Topical Collection "Polyelectrolytes"

Editors

Collection Editor
Dr. Christine Wandrey

Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC-GE, CH C1 392, station 6, CH-1015 Lausanne, Switzerland
Website | E-Mail
Fax: +41 21 693 96 85
Interests: water-soluble polymers; polyelectrolytes; polyelectrolyte complexes; hydrogels; biomaterials; radical polymerization/copolymerization; characterization of charged macromolecule; analytical ultracentrifugation
Collection Editor
Prof. Dr. Ruth Freitag

Chair for Process Biotechnology, Faculty of Engineering Sciences, University of Bayreuth, 95440 Bayreuth, Germany
Website | E-Mail
Fax: +49 921 55 7375
Interests: stimuli-responsive; materials; bioconjugates; synthetic biodelivery systems; bioseparation engineering; scaffolds for tissue engineering; encapsulation; monolithic stationary phases for chromatography and electrochromatography
Collection Editor
Dr. Ulrich Scheler

Head of teh Department Polyelectrolytes and Dispersions, Leibniz-Institut für Polymerforschung Dresden e.V., D-01069 Dresden, Germany
Website | E-Mail
Fax: +49 351 4658 231
Interests: structure, dynamics and charge in complex polymer and polyelectrolytes systems magnetic resonance (NMR & EPR) including methods developments

Topical Collection Information

Dear Colleagues,

Polyelectrolytes are the subject of very active research and development in fields such as chemistry, physics, biology, medicine, materials science, food science, and nanotechnology. Polyelectrolyte properties are intrinsic, not only to a multitude of single macromolecules, but also to their organized structures and molecular assemblies. Biopolymers, such as proteins, DNA, and polysaccharides, which are available in almost unlimited quantity in nature, as well as many synthetic polymers, which are industrially produced on a large scale, belong to this fascinating class of polymers. The importance of polyelectrolyte research is best documented by the exponential annual increase of scientific publications dedicated to polyelectrolytes.

This Topical Collection of Polymers intends to serve as an interdisciplinary platform addressing all polyelectrolyte related aspects. Overcoming the hurdles of single research disciplines will be the major goal of this platform. Original articles reporting recent progress on polyelectrolyte related research from different disciplines and review papers highlighting in particular interdisciplinary aspects are both invited. Launched in 2015, this Topical Collection remains open for submissions. We are looking forward to receiving your paper at any time.

Dr. Christine Wandrey
Prof. Dr. Ruth Freitag
Dr. Ulrich Scheler
Collection Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polyelectrolyte synthesis, modification and functionalization
  • advanced analysis and characterization of polyelectrolytes and their assemblies
  • thermodynamics, solubility, and phase diagrams
  • polyelectrolytes in solution and at interfaces
  • theory and simulations
  • polyelectrolyte phenomena
  • assemblies and multilayers
  • complexes and particles
  • conformation and counterions: theory vs. experiment
  • natural polyelectrolytes
  • synthetic polyelectrolytes
  • hybrid materials
  • polyelectrolytes in food and cosmetics
  • polyelectrolytes for biomaterials and pharmaceuticals
  • polyelectrolytes for industrial and environmental processes

Related Special Issues

Published Papers (58 papers)

2019

Jump to: 2018, 2017, 2016, 2015, 2014, 2011, 2010

Open AccessArticle Gelatin Films Modified with Acidic and Polyelectrolyte Polymers—Material Selection for Soft Gastroresistant Capsules
Polymers 2019, 11(2), 338; https://doi.org/10.3390/polym11020338
Received: 8 December 2018 / Revised: 4 February 2019 / Accepted: 10 February 2019 / Published: 15 February 2019
PDF Full-text (3099 KB) | HTML Full-text | XML Full-text
Abstract
The following investigation comprised the formation of acid-resistant gelatin-based films, intended for future use in soft-capsule technology. Such film compositions were obtained by including nonionized forms of acid-insoluble polymers in a gelatin-based film-forming mixture. The selected films were additionally modified with small amounts [...] Read more.
The following investigation comprised the formation of acid-resistant gelatin-based films, intended for future use in soft-capsule technology. Such film compositions were obtained by including nonionized forms of acid-insoluble polymers in a gelatin-based film-forming mixture. The selected films were additionally modified with small amounts of anionic polysaccharides that have potential to interact with gelatin, forming polyelectrolyte complexes. The obtained film compositions were subjected to, e.g., disintegration tests, adhesiveness tests, differential scanning calorimetry (DSC), and a transparency study. As a result of the performed study, some commercial enteric polymers (acrylates), as well as cellulose acetate phthalate, were selected as components that have the ability to coalesce and form a continuous phase within a gelatin film. The use of a small amount (1.5%) of additional gelling polymers improved the rheological characteristics and adhesive properties of the obtained films, with ί-carrageenan and gellan gum appearing to be the most beneficial. Full article
Figures

Graphical abstract

Open AccessArticle Upper Critical Solution Temperature (UCST) Behavior of Polystyrene-Based Polyampholytes in Aqueous Solution
Polymers 2019, 11(2), 265; https://doi.org/10.3390/polym11020265
Received: 15 December 2018 / Revised: 22 January 2019 / Accepted: 2 February 2019 / Published: 4 February 2019
PDF Full-text (2389 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates [...] Read more.
Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates the degree of polymerization (n = 20 or 97). The percentage VBTAC content in P(VBTAC/NaSS)n is always about 50 mol%, as revealed by 1H NMR measurements, meaning that P(VBTAC/NaSS)n is a close to stoichiometrically charge-neutralized polymer. Although P(VBTAC/NaSS)n cannot dissolve in pure water at room temperature, the addition of NaCl or heating solubilizes the polymers. Furthermore, P(VBTAC/NaSS)n exhibits upper critical solution temperature (UCST) behavior in aqueous NaCl solutions. The UCST is shifted to higher temperatures by increasing the polymer concentration and molecular weight, and by decreasing the NaCl concentration. The UCST behavior was measured ranging the polymer concentrations from 0.5 to 5.0 g/L. Full article
Figures

Graphical abstract

Open AccessArticle Layer-by-Layer Assembly and Electrochemical Study of Alizarin Red S-Based Thin Films
Polymers 2019, 11(1), 165; https://doi.org/10.3390/polym11010165
Received: 4 December 2018 / Revised: 21 December 2018 / Accepted: 2 January 2019 / Published: 18 January 2019
PDF Full-text (3575 KB) | HTML Full-text | XML Full-text
Abstract
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the [...] Read more.
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the complementary polymer. Unconventional LbL methods, including co-adsorption of ARS and poly(4-styrene sulfonate) (PSS) with BPEI to assemble (BPEI/(ARS+PSS))n, as well as pre-complexation of ARS with BPEI and further assembly with PSS to fabricate ((BPEI+ARS)/PSS)n, are designed for investigation and comparison. Film growth patterns, UV–Vis spectra and surface morphology of the three types of LbL assemblies are measured and compared to reveal the formation mechanism of the LbL films. Electrochemical properties including cyclic voltammetry and spectroelectrochemistry of (BPEI/ARS)120, (BPEI/(ARS+PSS))120 and ((BPEI+ARS)/PSS)120 films are studied, and the results show a slight color change due to the redox reaction of ARS. ((BPEI+ARS)/PSS)120 shows the best stability among the three samples. It is concluded that the manner of dye- incorporation has a great effect on the electrochemical properties of the resultant films. Full article
Figures

Graphical abstract

Open AccessArticle Polyelectrolyte Complexation of Oligonucleotides by Charged Hydrophobic—Neutral Hydrophilic Block Copolymers
Polymers 2019, 11(1), 83; https://doi.org/10.3390/polym11010083
Received: 10 December 2018 / Revised: 1 January 2019 / Accepted: 2 January 2019 / Published: 7 January 2019
PDF Full-text (5846 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polyelectrolyte complex micelles (PCMs, core-shell nanoparticles formed by complexation of a polyelectrolyte with a polyelectrolyte-hydrophilic neutral block copolymer) offer a solution to the critical problem of delivering therapeutic nucleic acids, Despite this, few systematic studies have been conducted on how parameters such as [...] Read more.
Polyelectrolyte complex micelles (PCMs, core-shell nanoparticles formed by complexation of a polyelectrolyte with a polyelectrolyte-hydrophilic neutral block copolymer) offer a solution to the critical problem of delivering therapeutic nucleic acids, Despite this, few systematic studies have been conducted on how parameters such as polycation charge density, hydrophobicity, and choice of charged group influence PCM properties, despite evidence that these strongly influence the complexation behavior of polyelectrolyte homopolymers. In this article, we report a comparison of oligonucleotide PCMs and polyelectrolyte complexes formed by poly(lysine) and poly((vinylbenzyl) trimethylammonium) (PVBTMA), a styrenic polycation with comparatively higher charge density, increased hydrophobicity, and a permanent positive charge. All of these differences have been individually suggested to provide increased complex stability, but we find that PVBTMA in fact complexes oligonucleotides more weakly than does poly(lysine), as measured by stability versus added salt. Using small angle X-ray scattering and electron microscopy, we find that PCMs formed from both cationic blocks exhibit very similar structure-property relationships, with PCM radius determined by the cationic block size and shape controlled by the hybridization state of the oligonucleotides. These observations narrow the design space for optimizing therapeutic PCMs and provide new insights into the rich polymer physics of polyelectrolyte self-assembly. Full article
Figures

Graphical abstract

Open AccessReview Protein–Polyelectrolyte Interaction: Thermodynamic Analysis Based on the Titration Method
Polymers 2019, 11(1), 82; https://doi.org/10.3390/polym11010082
Received: 28 November 2018 / Revised: 26 December 2018 / Accepted: 2 January 2019 / Published: 7 January 2019
PDF Full-text (5093 KB) | HTML Full-text | XML Full-text
Abstract
This review discussed the mechanisms including theories and binding stages concerning the protein–polyelectrolyte (PE) interaction, as well as the applications for both complexation and coacervation states of protein–PE pairs. In particular, this review focused on the applications of titration techniques, that is, turbidimetric [...] Read more.
This review discussed the mechanisms including theories and binding stages concerning the protein–polyelectrolyte (PE) interaction, as well as the applications for both complexation and coacervation states of protein–PE pairs. In particular, this review focused on the applications of titration techniques, that is, turbidimetric titration and isothermal titration calorimetry (ITC), in understanding the protein–PE binding process. To be specific, by providing thermodynamic information such as pHc, pHφ, binding constant, entropy, and enthalpy change, titration techniques could shed light on the binding affinity, binding stoichiometry, and driving force of the protein–PE interaction, which significantly guide the applications by utilization of these interactions. Recent reports concerning interactions between proteins and different types of polyelectrolytes, that is, linear polyelectrolytes and polyelectrolyte modified nanoparticles, are summarized with their binding differences systematically discussed and compared based on the two major titration techniques. We believe this short review could provide valuable insight in the understanding of the structure–property relationship and the design of applied biomedical PE-based systems with optimal performance. Full article
Figures

Figure 1

2018

Jump to: 2019, 2017, 2016, 2015, 2014, 2011, 2010

Open AccessReview Intermolecular Interactions in Polyelectrolyte and Surfactant Complexes in Solution
Polymers 2019, 11(1), 51; https://doi.org/10.3390/polym11010051
Received: 29 November 2018 / Revised: 20 December 2018 / Accepted: 28 December 2018 / Published: 31 December 2018
PDF Full-text (4484 KB) | HTML Full-text | XML Full-text
Abstract
Polyelectrolytes are an important class of polymeric materials and are increasingly used in complex industrial formulations. A core use of these materials is in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions drives unique solution behavior and structure formation. In [...] Read more.
Polyelectrolytes are an important class of polymeric materials and are increasingly used in complex industrial formulations. A core use of these materials is in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions drives unique solution behavior and structure formation. In this review, we apply a molecular level perspective to the broad literature on polyelectrolyte-surfactant complexes, discussing explicitly the hydrophobic and electrostatic interaction contributions to polyelectrolyte surfactant complexes (PESCs), as well as the interplay between the two molecular interaction types. These interactions are sensitive to a variety of solution conditions, such as pH, ionic strength, mixing procedure, charge density, etc. and these parameters can readily be used to control the concentration at which structures form as well as the type of structure in the bulk solution. Full article
Figures

Graphical abstract

Open AccessReview Exploring Structure–Property Relationships of GAGs to Tailor ECM-Mimicking Hydrogels
Polymers 2018, 10(12), 1376; https://doi.org/10.3390/polym10121376
Received: 22 October 2018 / Revised: 3 December 2018 / Accepted: 9 December 2018 / Published: 11 December 2018
PDF Full-text (1593 KB) | HTML Full-text | XML Full-text
Abstract
Glycosaminoglycans (GAGs) are a class of linear polysaccharides that are ubiquitous in the extracellular matrix (ECM) and on cell surfaces. Due to their key role in development, homeostasis, pathogenesis, and regeneration, GAGs are increasingly used in the design of ECM-mimicking hydrogels to stimulate [...] Read more.
Glycosaminoglycans (GAGs) are a class of linear polysaccharides that are ubiquitous in the extracellular matrix (ECM) and on cell surfaces. Due to their key role in development, homeostasis, pathogenesis, and regeneration, GAGs are increasingly used in the design of ECM-mimicking hydrogels to stimulate tissue formation and regenerative processes via specifically orchestrated cell-instructive signals. These applications first and foremost build on the ability of GAGs to effectively bind, protect, and release morphogens. The specificity and strength of morphogen-GAG interactions are largely governed by the number and spatial distribution of negatively charged sulfate groups carried by GAGs. Herein, we summarize a mean-field approach to quantify the density of ionizable groups, GAG concentration, and cross-linking degree of GAG-containing hydrogels on the basis of microslit electrokinetic experiments. We further present and discuss a continuum model of mucosa that accounts for charge regulation by glycan-ion pairing in biological contexts and under conditions of macromolecular crowding. Finally, we discuss the modulation of the morphogen binding and transport in GAG hydrogels by selective desulfation of the GAG component. Full article
Figures

Figure 1

Open AccessArticle Separation and Characterization of Highly Charged Polyelectrolytes Using Free-Solution Capillary Electrophoresis
Polymers 2018, 10(12), 1331; https://doi.org/10.3390/polym10121331
Received: 26 October 2018 / Revised: 26 November 2018 / Accepted: 27 November 2018 / Published: 2 December 2018
PDF Full-text (2038 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The characterization of statistical copolymers of various charge densities remains an important and challenging analytical issue. Indeed, the polyelectrolyte (PE) effective electrophoretic mobility tends to level off above a certain charge density, due to the occurrence of Manning counterion condensation. Surprisingly, we demonstrate [...] Read more.
The characterization of statistical copolymers of various charge densities remains an important and challenging analytical issue. Indeed, the polyelectrolyte (PE) effective electrophoretic mobility tends to level off above a certain charge density, due to the occurrence of Manning counterion condensation. Surprisingly, we demonstrate in this work that it is possible to get highly resolutive separations of charged PE using free-solution capillary electrophoresis, even above the critical value predicted by the Manning counterion condensation theory. Full separation of nine statistical poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonate) polymers of different charge densities varying between 3% and 100% was obtained by adjusting the ionic strength of the background electrolyte (BGE) in counter electroosmotic mode. Distributions of the chemical charge density could be obtained for the nine PE samples, showing a strong asymmetry of the distribution for the highest-charged PE. This asymmetry can be explained by the different reactivity ratios during the copolymerization. To shed more light on the separation mechanism, effective and apparent selectivities were determined by a systematic study and modeling of the electrophoretic mobility dependence according to the ionic strength. It is demonstrated that the increase in resolution with increasing BGE ionic strength is not only due to a closer matching of the electroosmotic flow magnitude with the PE electrophoretic effective mobility, but also to an increase of the dependence of the PE effective mobility according to the charge density. Full article
Figures

Graphical abstract

Open AccessArticle Switchable Release of Bone Morphogenetic Protein from Thermoresponsive Poly(NIPAM-co-DMAEMA)/Cellulose Sulfate Particle Coatings
Polymers 2018, 10(12), 1314; https://doi.org/10.3390/polym10121314
Received: 26 October 2018 / Revised: 20 November 2018 / Accepted: 22 November 2018 / Published: 27 November 2018
PDF Full-text (3638 KB) | HTML Full-text | XML Full-text
Abstract
Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C [...] Read more.
Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C shrinking to RH = 74–103 nm at T = 60 °C. Obviously, PNIPAM-DMAEMA/CS undergoes volume phase transition (VPT) analogously to pure PNIPAM, when critical VPT temperature (VPTT) is exceeded. Temperature dependent turbidity measurements revealed broad VPT and VPTT 47 °C for PNIPAM-DMAEMA/CS colloid dispersions at pH = 7.0. FTIR spectroscopy on thermoresponsive PNIPAM-DMAEMA/CS particle coatings at germanium model substrates under HEPES buffer indicated both wet-adhesiveness and VPT behavior based on diagnostic band intensity increases with temperature. From respective temperature courses empirical VPTT ≈ 42 °C for PNIPAM-DMAEMA/CS coatings at pH = 7.0 were found, which were comparable to VPTT found for respective dispersions. Finally, the PNIPAM-DMAEMA/CS coatings were loaded with BMP-2 and model protein papain (PAP). Time dependent FTIR spectroscopic measurements showed, that for T = 37 °C there was a relative protein release of ≈30% for PAP and ≈10% for BMP-2 after 24 h, which did not increase further. Heating to T = 42 °C for PAP and to 47 °C for BMP-2 further secondary protein release of ≈20% after 24 h was found, respectively, interesting for clinical applications. BMP-2 eluted even at 47 °C was found to be still biologically active. Full article
Figures

Figure 1

Open AccessArticle Effect of the Surface Hydrophobicity Degree on the In Vitro Release of Polar and Non-Polar Drugs from Polyelectrolyte Matrix Tablets
Polymers 2018, 10(12), 1313; https://doi.org/10.3390/polym10121313
Received: 30 October 2018 / Revised: 23 November 2018 / Accepted: 23 November 2018 / Published: 27 November 2018
PDF Full-text (5081 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This work is the continuation of a series of studies focused on establishing the relationship between the surface thermodynamic properties of polyelectrolyte matrix tablets and drug release mechanisms. In this case, two model drugs with different polarity features, such as carbamazepine (non-polar) and [...] Read more.
This work is the continuation of a series of studies focused on establishing the relationship between the surface thermodynamic properties of polyelectrolyte matrix tablets and drug release mechanisms. In this case, two model drugs with different polarity features, such as carbamazepine (non-polar) and metoprolol succinate (polar) were used in combination with polymeric material hydroxypropyl-methyl cellulose (HPMC) and two polyelectrolytes derived from maleic anhydride corresponding to the sodium salts of poly(maleic acid-alt-ethylene) and poly(maleic acid-alt-octadecene) named PAM-0Na and PAM-18Na, respectively. The polymers were obtained and characterized as reported previously. Surface studies were performed by the sessile drop method, whilst the surface free energy was determined through Owens, Wendt, Rable and Kaeble (OWRK) semi-empirical model. By contrast, the drug release studies were performed by in vitro dissolution tests, where data were analyzed through dissolution efficiency. The results showed that, depending on the drug polarity, type and polymer proportion, surface properties and drug release processes are significantly affected. Full article
Figures

Graphical abstract

Open AccessArticle Design of Oligonucleotide Carriers: Importance of Polyamine Chain Length
Polymers 2018, 10(12), 1297; https://doi.org/10.3390/polym10121297
Received: 22 October 2018 / Revised: 16 November 2018 / Accepted: 21 November 2018 / Published: 23 November 2018
PDF Full-text (7748 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Amine containing polymers are extensively studied as special carriers for short-chain RNA (13–25 nucleotides), which are applied as gene silencing agents in gene therapy of various diseases including cancer. Elaboration of the oligonucleotide carriers requires knowledge about peculiarities of the oligonucleotide–polymeric amine interaction. [...] Read more.
Amine containing polymers are extensively studied as special carriers for short-chain RNA (13–25 nucleotides), which are applied as gene silencing agents in gene therapy of various diseases including cancer. Elaboration of the oligonucleotide carriers requires knowledge about peculiarities of the oligonucleotide–polymeric amine interaction. The critical length of the interacting chains is an important parameter which allows us to design sophisticated constructions containing oligonucleotide binding segments, solubilizing, protective and aiming parts. We studied interactions of (TCAG)n, n = 1–6 DNA oligonucleotides with polyethylenimine and poly(N-(3-((3-(dimethylamino)propyl)(methyl)amino)propyl)-N-methylacrylamide). The critical length for oligonucleotides in interaction with polymeric amines is 8–12 units and complexation at these length can be accompanied by “all-or-nothing” effects. New dimethylacrylamide based polymers with grafted polyamine chains were obtained and studied in complexation with DNA and RNA oligonucleotides. The most effective interaction and transfection activity into A549 cancer cells and silencing efficiency against vascular endothelial growth factor (VEGF) was found for a sample with average number of nitrogens in polyamine chain equal to 27, i.e., for a sample in which all grafted chains are longer than the critical length for polymeric amine–oligonucleotide complexation. Full article
Figures

Graphical abstract

Open AccessArticle Conformation Study of Dual Stimuli-Responsive Core-Shell Diblock Polymer Brushes
Polymers 2018, 10(10), 1084; https://doi.org/10.3390/polym10101084
Received: 30 August 2018 / Revised: 26 September 2018 / Accepted: 28 September 2018 / Published: 30 September 2018
PDF Full-text (3022 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Stimuli-responsive nanoparticles are among the most popular research topics. In this study, two types of core-shell (polystyrene with a photoiniferter (PSV) as the core and diblock as the shell) polymer brushes ([email protected]b-PAA and [email protected]b-PNIPA) were designed and prepared using [...] Read more.
Stimuli-responsive nanoparticles are among the most popular research topics. In this study, two types of core-shell (polystyrene with a photoiniferter (PSV) as the core and diblock as the shell) polymer brushes ([email protected]b-PAA and [email protected]b-PNIPA) were designed and prepared using surface-initiated photoiniferter-mediated polymerization (SI-PIMP). Moreover, their pH- and temperature-stimuli responses were explored by dynamic light scattering (DLS) and turbidimeter under various conditions. The results showed that the conformational change was determined on the basis of the competition among electrostatic repulsion, hydrophobic interaction, hydrogen bonding, and steric hindrance, which was also confirmed by protein adsorption experiments. These results are not only helpful for the design and synthesis of stimuli-responsive polymer brushes but also shed light on controlled protein immobilization under mild conditions. Full article
Figures

Graphical abstract

Open AccessArticle Sulfonated Poly(Arylene Ether Sulfone) and Perfluorosulfonic Acid Composite Membranes Containing Perfluoropolyether Grafted Graphene Oxide for Polymer Electrolyte Membrane Fuel Cell Applications
Polymers 2018, 10(6), 569; https://doi.org/10.3390/polym10060569
Received: 23 April 2018 / Revised: 21 May 2018 / Accepted: 22 May 2018 / Published: 23 May 2018
Cited by 3 | PDF Full-text (2273 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end [...] Read more.
Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end group onto the surface of GO via ring opening reaction between the carboxylic acid group in poly(hexafluoropropylene oxide) and the epoxide groups in GO, using 4-dimethylaminopyridine as a base catalyst. Both SPAES and PFSA composite membranes containing PFPE-GO showed much improved mechanical strength and dimensional stability, compared to each linear SPAES and PFSA membrane, respectively. The enhanced mechanical strength and dimensional stability of composite membranes can be ascribed to the homogeneous dispersion of rigid conjugated carbon units in GO through the increased interfacial interactions between PFPE-GO and SPAES/PFSA matrices. Full article
Figures

Graphical abstract

Open AccessArticle Effect of Counterion Valence on Conformational Behavior of Spherical Polyelectrolyte Brushes Confined between Two Parallel Walls
Polymers 2018, 10(4), 363; https://doi.org/10.3390/polym10040363
Received: 22 February 2018 / Revised: 21 March 2018 / Accepted: 22 March 2018 / Published: 24 March 2018
PDF Full-text (17800 KB) | HTML Full-text | XML Full-text
Abstract
We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. [...] Read more.
We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. For the monovalent case, the increase of the charge fraction leads to extended brush conformation for different slit width (distance between two walls) but collapsed brush in the presence of trivalent counterions is observed. The confinement does not affect electrostatic correlation between trivalent counterions and charged monomers. However, it was found that narrow slit width contributes to stronger electrostatic correlation for the monovalent case. This is because more monovalent counterions are inside the brush at strong confinement, but almost all trivalent counterions are trapped into the brush independently of the slit width. The diffusion of counterions under the confinement is related to the electrostatic correlation. Our simulations also reveal that the brush thickness depends on the slit width nonlinearly. Full article
Figures

Figure 1

2017

Jump to: 2019, 2018, 2016, 2015, 2014, 2011, 2010

Open AccessArticle Hydrophilic Polyelectrolyte Multilayers Improve the ELISA System: Antibody Enrichment and Blocking Free
Polymers 2017, 9(2), 51; https://doi.org/10.3390/polym9020051
Received: 19 December 2016 / Revised: 17 January 2017 / Accepted: 24 January 2017 / Published: 12 February 2017
Cited by 4 | PDF Full-text (1955 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as [...] Read more.
In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as cationic and anionic polyelectrolytes. On the negatively-charged (PDDA/PAA)3 polyelectrolyte multilayers the hydrophilic PAA surface could efficiently decrease the magnitude of the noise signal, by inhibiting nonspecific adsorption even without blocking reagent adsorption. Moreover, the (PDDA/PAA)3 substrate covalently immobilized the primary antibody, greatly increasing the amount of primary antibody adsorption and enhancing the specific detection signal compared with a conventional PS plate. The calibration curve of the (PDDA/PAA)3 substrate showed a wide linear range, for concentrations from 0.033 to 33 nM, a large specific signal change, and a detection limit of 33 pM, even though the conventional blocking reagent adsorption step was omitted. The (PDDA/PAA)3 substrate provided a high-performance ELISA system with a simple fabrication process and high sensitivity; the system presented here shows potential for a variety of immunosensor applications. Full article
Figures

Graphical abstract

Open AccessArticle The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes
Polymers 2017, 9(2), 50; https://doi.org/10.3390/polym9020050
Received: 19 November 2016 / Revised: 11 January 2017 / Accepted: 19 January 2017 / Published: 4 February 2017
Cited by 6 | PDF Full-text (2024 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) [...] Read more.
The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) molar mass on the interaction with statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been systematically investigated for different PAMAMPS chemical charge densities (15% and 100%) and different ionic strengths. The study of the ionic strength dependence of the binding constant allowed the determination of the total number of released counter-ions during the formation of the PEC, which can be compared to the total number of counter-ions initially condensed on the individual polyelectrolyte partners before the association. Interestingly, this fraction of released counter-ions, which was strongly dependent on the PLL molar mass, was almost independent of the PAMAMPS charge density. These findings are useful to predict the binding constant according to the molar mass and charge density of the polyelectrolyte partners. Full article
Figures

Graphical abstract

Open AccessArticle Polyion Complex Vesicles with Solvated Phosphobetaine Shells Formed from Oppositely Charged Diblock Copolymers
Polymers 2017, 9(2), 49; https://doi.org/10.3390/polym9020049
Received: 31 December 2016 / Revised: 24 January 2017 / Accepted: 30 January 2017 / Published: 4 February 2017
Cited by 9 | PDF Full-text (3860 KB) | HTML Full-text | XML Full-text
Abstract
Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer [...] Read more.
Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer agent. The degree of polymerization for PMPC, cationic PMAPTAC, and anionic PAMPS blocks was 20, 190, and 196, respectively. Combining two solutions of oppositely charged diblock copolymers, PMPC-b-PMAPTAC and PMPC-b-PAMPS, led to the spontaneous formation of polyion complex vesicles (PICsomes). The PICsomes were characterized using 1H NMR, static abd dynamic light scattering, transmittance electron microscopy (TEM), and atomic force microscopy. Maximum hydrodynamic radius (Rh) for the PICsome was observed at a neutral charge balance of the cationic and anionic diblock copolymers. The Rh value and aggregation number (Nagg) of PICsomes in 0.1 M NaCl was 78.0 nm and 7770, respectively. A spherical hollow vesicle structure was observed in TEM images. The hydrodynamic size of the PICsomes increased with concentration of the diblock copolymer solutions before mixing. Thus, the size of the PICsomes can be controlled by selecting an appropriate preparation method. Full article
Figures

Graphical abstract

Open AccessReview Engineering Cell Surfaces with Polyelectrolyte Materials for Translational Applications
Polymers 2017, 9(2), 40; https://doi.org/10.3390/polym9020040
Received: 11 December 2016 / Revised: 18 January 2017 / Accepted: 19 January 2017 / Published: 28 January 2017
Cited by 3 | PDF Full-text (4330 KB) | HTML Full-text | XML Full-text
Abstract
Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field. [...] Read more.
Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field. Over the past decade, modification of cell surfaces with natural or synthetic materials has been studied to exploit this complexity for both fundamental and translational goals. In this review we present the existing biomedical technologies for engineering cell surfaces with one important class of materials, polyelectrolytes. We begin by introducing the challenges facing the cell surface engineering field. We then discuss the features of polyelectrolytes and how these properties can be harnessed to solve challenges in cell therapy, tissue engineering, cell-based drug delivery, sensing and tracking, and immune modulation. Throughout the review, we highlight opportunities to drive the field forward by bridging new knowledge of polyelectrolytes with existing translational challenges. Full article
Figures

Figure 1

Open AccessArticle Polymer Conformations in Ionic Microgels in the Presence of Salt: Theoretical and Mesoscale Simulation Results
Polymers 2017, 9(1), 15; https://doi.org/10.3390/polym9010015
Received: 21 November 2016 / Revised: 22 December 2016 / Accepted: 29 December 2016 / Published: 5 January 2017
Cited by 14 | PDF Full-text (1109 KB) | HTML Full-text | XML Full-text
Abstract
We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account [...] Read more.
We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account explicitly, and charge-charge interactions are described by the Coulomb potential. By varying the charge interaction strength and salt concentration, we characterize the swelling of the polyelectrolytes and the charge distribution. In particular, we determine the amount of trapped mobile charges inside the microgel and the Debye screening length. Moreover, we analyze the polymer extension theoretically in terms of the tension blob model taking into account counterions and salt ions implicitly by the Debye–Hückel model. Our studies reveal a strong dependence of the amount of ions absorbed in the interior of the microgel on the electrostatic interaction strength, which is related to the degree of the gel swelling. This implies a dependence of the inverse Debye screening length κ on the ion concentration; we find a power-law increase of κ with the Coulomb interaction strength with the exponent 3 / 5 for a salt-free microgel and an exponent 1 / 2 for moderate salt concentrations. Additionally, the radial dependence of polymer conformations and ion distributions is addressed. Full article
Figures

Graphical abstract

2016

Jump to: 2019, 2018, 2017, 2015, 2014, 2011, 2010

Open AccessArticle Influence of Polyelectrolyte Multilayer Properties on Bacterial Adhesion Capacity
Polymers 2016, 8(10), 345; https://doi.org/10.3390/polym8100345
Received: 16 August 2016 / Revised: 11 September 2016 / Accepted: 14 September 2016 / Published: 26 September 2016
Cited by 3 | PDF Full-text (8966 KB) | HTML Full-text | XML Full-text
Abstract
Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were [...] Read more.
Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were determined by atomic force microscopy and tensiometry. The surface charge was examined by the zeta potential measurements of silica particles covered with polyelectrolyte multilayers, whereby ionic strength and polyelectrolyte concentrations significantly influenced the build-up process. For adhesion experiments, we used the bacterium Pseudomonas aeruginosa. The extent of adhered bacteria on the surface was determined by scanning electron microscopy. The results showed that the extent of adhered bacteria mostly depends on the type of terminating polyelectrolyte layer, since relatively low differences in surface roughness and hydrophobicity were obtained. In the case of polyelectrolyte multilayers terminating with a positively charged layer, bacterial adhesion was more pronounced than in the case when the polyelectrolyte layer was negatively charged. Full article
Figures

Graphical abstract

Open AccessCommunication Rheological Properties of DNA Molecules in Solution: Molecular Weight and Entanglement Influences
Polymers 2016, 8(8), 279; https://doi.org/10.3390/polym8080279
Received: 17 June 2016 / Revised: 25 July 2016 / Accepted: 29 July 2016 / Published: 3 August 2016
Cited by 2 | PDF Full-text (434 KB) | HTML Full-text | XML Full-text
Abstract
Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA [...] Read more.
Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA from salmon sperm was purified and then studied in solutions in a wide concentration range (between 0.5 and 1600 mg/mL). The intrinsic viscosity of this low molecular weight DNA sample was firstly determined and the evidence of the overlap concentration was detected around the concentration of 125 mg/mL. The chain characteristics of these short molecules were studied in terms of the influence of their molecular weight on the solution viscosities and on the overlap parameter CDNA[η]. Furthermore, to complete previously reported experimental data, solutions of a large molecular weight DNA from calf-thymus were studied in a high concentration range (up to 40 mg/mL). The rheological behavior is discussed in terms of the generalized master curve obtained from the variation of the specific viscosity at zero shear rate (ηsp,0) as a function of CDNA[η]. Full article
Figures

Graphical abstract

Open AccessArticle Physicochemical Properties of Biopolymer Hydrogels Treated by Direct Electric Current
Polymers 2016, 8(7), 248; https://doi.org/10.3390/polym8070248
Received: 22 April 2016 / Revised: 17 June 2016 / Accepted: 27 June 2016 / Published: 12 July 2016
Cited by 6 | PDF Full-text (2414 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC) [...] Read more.
The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC) of 400 mA for a duration of five minutes. There were three types of gels prepared for the purpose of the study: C, control; H, gels on the basis of hydrosols that were treated with DC; and G, gels treated with DC. In the course of the study, the authors carried out the following analyses: Texture Profile Analysis (TPA), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Swelling Ratio (SR). Furthermore, the color and pH of hydrogels were measured. The FTIR spectra showed that the structures of gelatine, carrageenan and sodium alginate do not significantly change upon applying DC. The results of TPA, SR, color and pH measurement indicate that hydrogels’ properties are significantly dependent on the type of polymer, its concentration and the type of the gel. By changing those parameters, the characteristics of such gels can be additionally tuned, which extends their applicability, e.g., in the food industry. Moreover, the analysis revealed that SR of H gel gelatine after 72 h of storage was 1.84-times higher than SR of the control sample, which indicated that this gel may be considered as a possible component for wound dressing materials. Full article
Figures

Figure 1

Open AccessArticle Effect of Very High Charge Density and Monomer Constitution on the Synthesis and Properties of Cationic Polyelectrolytes
Polymers 2016, 8(6), 234; https://doi.org/10.3390/polym8060234
Received: 8 March 2016 / Revised: 16 May 2016 / Accepted: 30 May 2016 / Published: 16 June 2016
PDF Full-text (3599 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The [...] Read more.
The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The high level of counterion condensation reduces the ionic strength in the polymerizing batch when the monomer molecules connect to PEL chains. This has the consequence that the hydrodynamic and excluded volume of the PEL molecules will change. Studies of the free radical polymerization revealed non-ideal polymerization kinetics already at low conversion and additionally autoacceleration above a certain monomer concentration and conversion. Similar autoacceleration was not observed for monomers yielding PEL with charge spacing of 0.25 or 0.5 nm. Coulomb interactions, monomer association, steric effects, and specific features of the monomer constitution have been evaluated concerning their contributions to the concentration dependence and conversion dependence of kinetic parameters. The different backbone constitutions of di-M and di-A not only influence the polymerization kinetics but also equip poly(di-M) with higher hydrolytic stability. The experimental results confirm the impact of electrochemical parameters and the necessity to reconsider their inclusion in kinetic models. Full article
Figures

Graphical abstract

Open AccessArticle SANS from Salt-Free Aqueous Solutions of Hydrophilic and Highly Charged Star-Branched Polyelectrolytes
Polymers 2016, 8(6), 228; https://doi.org/10.3390/polym8060228
Received: 29 February 2016 / Revised: 14 May 2016 / Accepted: 23 May 2016 / Published: 8 June 2016
Cited by 4 | PDF Full-text (1593 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q1 [...] Read more.
Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q1*, is related to a position order between star cores and scales as q1* ∝ c1/3. The second, of abscissa q2*, is also observed in the scattering function of a semi-dilute solution of NaPSS linear polyelectrolytes. In the dilute regime (c < c*, non-overlapping stars), peak abscissa does not depend on concentration c and is just an intramolecular characteristic associated with the electrostatic repulsion between arms of the same star. In the semi-dilute regime, due to the star interpenetration, the scattering function – through the peak position, reflects repulsion between arms of the same star or of different stars. The c threshold between these distinct c-dependencies of q2* in the dilute and semi-dilute regimes is estimated as c*. Just as simple is the measurement of the geometrical radius R of the star obtained from the q1* value at c* through the relation 2R = 2π/q1*. By considering NaPSS stars of the same functionality with different degrees of polymerization per arm Na, we find R scaling linearly with Na, suggesting an elongated average conformation of the arms. This is in agreement with theoretical predictions and simulations. Meanwhile the value of q2* measured in the dilute regime does not allow any inhomogeneous counterion distribution inside the stars to be revealed. Full article
Figures

Graphical abstract

Open AccessArticle Influence of Polyplex Formation on the Performance of Star-Shaped Polycationic Transfection Agents for Mammalian Cells
Polymers 2016, 8(6), 224; https://doi.org/10.3390/polym8060224
Received: 12 April 2016 / Revised: 30 May 2016 / Accepted: 1 June 2016 / Published: 6 June 2016
Cited by 6 | PDF Full-text (2023 KB) | HTML Full-text | XML Full-text
Abstract
Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have [...] Read more.
Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have never before been compared side-by-side, e.g., in view of structural effects. Herein four star-shaped polycationic structures, all based on (2-dimethylamino) ethyl methacrylate (DMAEMA) building blocks, were investigated for their potential to deliver DNA to adherent (CHO, L929, HEK-293) and non-adherent (Jurkat, primary human T lymphocytes) mammalian cells. The investigated vectors included three structures where the PDMAEMA arms (different arm length and grafting densities) had been grown from a center silsesquioxane or silica-coated γ-Fe2O3-core and one micellar structure self-assembled from poly(1,2-butadiene)-block PDMAEMA polymers. All nano-stars combined high transfection potential with excellent biocompatibility. The micelles slightly outperformed the covalently linked agents. For method development and optimization, the absolute amount of polycation added to the cells was more important than the N/P-ratio (ratio between polycation nitrogen and DNA phosphate), provided a lower limit was passed and enough polycation was present to overcompensate the negative charge of the plasmid DNA. Finally, the matrix (NaCl vs. HEPES-buffered glucose solution), but also the concentrations adjusted during polyplex formation, affected the results. Full article
Figures

Graphical abstract

Open AccessArticle Polypeptide-Nanoparticle Interactions and Corona Formation Investigated by Monte Carlo Simulations
Polymers 2016, 8(6), 203; https://doi.org/10.3390/polym8060203
Received: 19 February 2016 / Revised: 11 May 2016 / Accepted: 12 May 2016 / Published: 25 May 2016
Cited by 8 | PDF Full-text (4349 KB) | HTML Full-text | XML Full-text
Abstract
Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and [...] Read more.
Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and denaturation. In this paper, the impact of neutral and charged nanoparticles (NPs) is investigated by Monte Carlo simulations on polypeptide (PP) chains with primary structure based on bovine serum albumin. The influence of pH, salt valency, and NP surface charge density is systematically studied. It is found that the PP is extended at extreme pH, when no complex formation is observed, and folded at physiological pH. PP adsorption around oppositely-charged NPs strongly limits chain structural changes and modifies its acid/base properties. At physiological pH, the complex formation occurs only with positively-charged NPs. The presence of salts, in particular those with trivalent cations, introduces additional electrostatic interactions, resulting in a mitigation of the impact of negative NPs. Thus, the corona structure is less dense with locally-desorbed segments. On the contrary, very limited impact of salt cation valency is observed when NPs are positive, due to the absence of competitive effects between multivalent cations and NP. Full article
Figures

Graphical abstract

Open AccessFeature PaperArticle Porphyrin Diacid-Polyelectrolyte Assemblies: Effective Photocatalysts in Solution
Polymers 2016, 8(5), 180; https://doi.org/10.3390/polym8050180
Received: 19 March 2016 / Revised: 18 April 2016 / Accepted: 25 April 2016 / Published: 4 May 2016
Cited by 9 | PDF Full-text (7752 KB) | HTML Full-text | XML Full-text
Abstract
Developing effective and versatile photocatalytic systems is of great potential in solar energy conversion. Here we investigate the formation of supramolecular catalysts by electrostatic self-assembly in aqueous solution: Combining positively charged porphyrins with negatively charged polyelectrolytes leads to nanoscale assemblies where, next to [...] Read more.
Developing effective and versatile photocatalytic systems is of great potential in solar energy conversion. Here we investigate the formation of supramolecular catalysts by electrostatic self-assembly in aqueous solution: Combining positively charged porphyrins with negatively charged polyelectrolytes leads to nanoscale assemblies where, next to electrostatic interactions, π–π interactions also play an important role. Porphyrin diacid-polyelectrolyte assemblies exhibit a substantially enhanced catalytic activity for the light-driven oxidation of iodide. Aggregates with the hexavalent cationic porphyrin diacids show up to 22 times higher catalytic activity than the corresponding aggregates under neutral conditions. The catalytic activity can be increased by increasing the valency of the porphyrin and by choice of the loading ratio. The structural investigation of the supramolecular catalysts took place via atomic force microscopy and small angle neutron scattering. Hence, a new facile concept for the design of efficient and tunable self-assembled photocatalysts is presented. Full article
Figures

Figure 1

Open AccessArticle Evaluation of the Performance of Dual Polyelectrolyte Systems on the Re-Flocculation Ability of Calcium Carbonate Aggregates in Turbulent Environment
Polymers 2016, 8(5), 174; https://doi.org/10.3390/polym8050174
Received: 17 January 2016 / Revised: 28 March 2016 / Accepted: 18 April 2016 / Published: 29 April 2016
Cited by 2 | PDF Full-text (927 KB) | HTML Full-text | XML Full-text
Abstract
Flocculation can be used in turbulent environments resulting in floc breakage due to shearing. The degree of re-flocculation relates directly to product quality and process efficiency. This study aimed at looking for alternatives to improve the re-flocculation ability of aggregates when polyelectrolytes (PEL) [...] Read more.
Flocculation can be used in turbulent environments resulting in floc breakage due to shearing. The degree of re-flocculation relates directly to product quality and process efficiency. This study aimed at looking for alternatives to improve the re-flocculation ability of aggregates when polyelectrolytes (PEL) are used as flocculation agents. Moreover, because branched PEL have proved previously to lead to high flocculation efficiencies, the work presented focus on the improvement of the re-flocculation ability of branched PEL. Thus, a selection of branched polymers were used primarily as flocculation aid and after flocs break up a linear polymer was added to the system in order to improve re-flocculation. Different mixtures were tested with the objective to try to induce, during re-flocculation, complementary flocculation mechanisms, favoring the patching mechanism. Re-flocculation improved significantly with this strategy. Laser Diffraction Spectroscopy was used to monitor the flocculation and re-flocculation processes supplying information about the floc size and structure. Since inorganic materials, namely bentonite, have been widely used to improve the re-flocculation capacity of polyelectrolytes, the results of using dual polyelectrolyte systems were compared with the effect of adding bentonite to the system. Full article
Figures

Figure 1

Open AccessArticle Thermodynamic Analysis of the Conformational Transition in Aqueous Solutions of Isotactic and Atactic Poly(Methacrylic Acid) and the Hydrophobic Effect
Polymers 2016, 8(5), 168; https://doi.org/10.3390/polym8050168
Received: 25 January 2016 / Revised: 15 April 2016 / Accepted: 20 April 2016 / Published: 28 April 2016
Cited by 4 | PDF Full-text (3499 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) [...] Read more.
The affinity of amphiphilic compounds for water is important in various processes, e.g., in conformational transitions of biopolymers, protein folding/unfolding, partitioning of drugs in the living systems, and many others. Herein, we study the conformational transition of two isomer forms of poly(methacrylic acid) (PMA), isotactic (iPMA) and atactic (aPMA), in water. These isomers are chemically equivalent and differ only in the arrangement of functional groups along the chain. A complete thermodynamic analysis of the transition of the PMA chains from the compact to the extended form (comprising the conformational transition) in water in the presence of three alkali chlorides is conducted by determining the free energy, enthalpy, and entropy changes of the process as a function of temperature, and therefrom also the heat capacity change. The heat capacity change of the transition is positive (+20 J/K mol) for aPMA and negative (−50 J/K mol) for iPMA. This result suggests a different affinity of PMA isomers for water. The conformational transition of iPMA is parallel to the transfer of polar solutes into water, whereas that of aPMA agrees with the transfer of nonpolar solutes into water. Full article
Figures

Figure 1

Open AccessArticle Mesogenic Polyelectrolyte Gels Absorb Organic Solvents and Liquid Crystalline Molecules
Polymers 2016, 8(4), 148; https://doi.org/10.3390/polym8040148
Received: 28 January 2016 / Revised: 12 April 2016 / Accepted: 13 April 2016 / Published: 19 April 2016
Cited by 4 | PDF Full-text (1564 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper, mesogenic polyelectrolyte gels (MPEgels) tethering mesogenic groups on the side chains were synthesized from a mesogenic monomer and ionic monomer via a conventional radical polymerization process. The obtained MPEgels absorbed various organic solvents in a wide range of dielectric constants [...] Read more.
In this paper, mesogenic polyelectrolyte gels (MPEgels) tethering mesogenic groups on the side chains were synthesized from a mesogenic monomer and ionic monomer via a conventional radical polymerization process. The obtained MPEgels absorbed various organic solvents in a wide range of dielectric constants from chloroform (ε = 7.6) to DMSO (ε = 46.5). The electrostatic repulsion among the polymer chains and the osmotic pressure between the interior and exterior of the MPEgel is responsible for the high swelling ability, revealed by the common ion effect using tetra(n-hexyl)ammonium tetra(3,5-bis(trifluoromethyl)phenylborate (THATFPB). The obtained MPEgels could also absorb liquid crystalline molecules such as 4-cyano-4’-pentylbiphenyl (5CB), analogously caused by the above-mentioned polyelectrolyte characteristic. The MPEgels exhibited liquid crystal transition temperature (TNI) on differential scanning calorimetry (DSC) measurement, and the increase of the ionic group content lowered TNI. The MPEgels absorbing liquid crystalline molecules exhibited differing TNI, dependent on the compatibility of the mesogenic group on the side chain to the liquid crystalline molecule. Full article
Figures

Graphical abstract

Open AccessArticle Modification of Spherical Polyelectrolyte Brushes by Layer-by-Layer Self-Assembly as Observed by Small Angle X-ray Scattering
Polymers 2016, 8(4), 145; https://doi.org/10.3390/polym8040145
Received: 31 January 2016 / Revised: 14 March 2016 / Accepted: 8 April 2016 / Published: 15 April 2016
Cited by 7 | PDF Full-text (4109 KB) | HTML Full-text | XML Full-text
Abstract
Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the [...] Read more.
Multilayer modified spherical polyelectrolyte brushes were prepared through alternate deposition of positively charged poly(allylamine hydrochloride) (PAH) and negatively charged poly-l-aspartic acid (PAsp) onto negatively charged spherical poly(acrylic acid) (PAA) brushes (SPBs) on a poly(styrene) core. The charge reversal determined by the zeta potential indicated the success of layer-by-layer (LBL) deposition. The change of the structure during the construction of multilayer modified SPBs was observed by small-angle X-ray scattering (SAXS). SAXS results indicated that some PAH chains were able to penetrate into the PAA brush for the PAA-PAH double-layer modified SPBs whereas part of the PAH moved towards the outer layer when the PAsp layer was loaded to form a PAA-PAH-PAsp triple-layer system. The multilayer modified SPBs were stable upon changing the pH (5 to 9) and ionic strength (1 to 100 mM). The triple-layer modified SPBs were more tolerated to high pH (even at 11) compared to the double-layer ones. SAXS is proved to be a powerful tool for studying the inner structure of multilayer modified SPBs, which can establish guidelines for the a range of potential applications of multilayer modified SPBs. Full article
Figures

Graphical abstract

Open AccessReview Activated Charge-Reversal Polymeric Nano-System: The Promising Strategy in Drug Delivery for Cancer Therapy
Polymers 2016, 8(4), 99; https://doi.org/10.3390/polym8040099
Received: 29 January 2016 / Revised: 10 March 2016 / Accepted: 14 March 2016 / Published: 5 April 2016
Cited by 7 | PDF Full-text (3902 KB) | HTML Full-text | XML Full-text
Abstract
Various polymeric nanoparticles (NPs) with optimal size, tumor-targeting functionalization, or microenvironment sensitive characteristics have been designed to solve several limitations of conventional chemotherapy. Nano-sized polymeric drug carrier systems have remarkably great advantages in drug delivery and cancer therapy, which are still plagued with [...] Read more.
Various polymeric nanoparticles (NPs) with optimal size, tumor-targeting functionalization, or microenvironment sensitive characteristics have been designed to solve several limitations of conventional chemotherapy. Nano-sized polymeric drug carrier systems have remarkably great advantages in drug delivery and cancer therapy, which are still plagued with severe deficiencies, especially insufficient cellular uptake. Recently, surface charge of medical NPs has been demonstrated to play an important role in cellular uptake. NPs with positive charge show higher affinity to anionic cell membranes such that with more efficient cellular internalization, but otherwise cause severe aggregation and fast clearance in circulation. Thus, surface charge-reversal NPs, specifically activated at the tumor site, have shown to elegantly resolve the enhanced cellular uptake in cancer cells vs. non-specific protein adsorption dilemma. Herein, this review mainly focuses on the effect of tumor-site activated surface charge reversal NPs on tumor treatment, including the activated mechanisms and various applications in suppressing cancer cells, killing cancer stem cell and overcoming multidrug resistance, with the emphasis on recent research in these fields. With the comprehensive and in-depth understanding of the activated surface charge reversal NPs, this approach might arouse great interest of scientific research on enhanced efficient polymeric nano-carriers in cancer therapy. Full article
Figures

Graphical abstract

Open AccessArticle The Effect of Temperature Treatment on the Structure of Polyelectrolyte Multilayers
Polymers 2016, 8(4), 120; https://doi.org/10.3390/polym8040120
Received: 29 January 2016 / Revised: 14 March 2016 / Accepted: 24 March 2016 / Published: 2 April 2016
Cited by 5 | PDF Full-text (958 KB) | HTML Full-text | XML Full-text
Abstract
The study addresses the effect of thermal treatment on the internal structure of polyelectrolyte multilayers (PEMs). In order to get insight into the internal structure of PEMs, Neutron Reflectometry (NR) was used. PEMs with a deuterated inner block towards the substrate and a [...] Read more.
The study addresses the effect of thermal treatment on the internal structure of polyelectrolyte multilayers (PEMs). In order to get insight into the internal structure of PEMs, Neutron Reflectometry (NR) was used. PEMs with a deuterated inner block towards the substrate and a non-deuterated outer block were prepared and measured in 1% RH and in D2O before and after a thermal treatment. Complementarily, PEMs with the same number of layers but completely non-deuterated were investigated by ellipsometry. The analysis for the overall thickness (d), the average scattering length density (SLD) and the refractive index (n) indicate a degradation of the PEM. The loss in material is independent of the number of layers, i.e., only a constant part of the PEM is affected by degradation. The analysis of the internal structure revealed a more complex influence of thermal treatment on PEM structure. Only the outermost part of the PEM degenerates, while the inner part becomes denser during the thermal treatment. In addition, the swelling behavior of PEMs is influenced by the thermal treatment. The untreated PEM shows a well pronounced odd—even effect, i.e., PDADMAC-terminated PEMs take up more water than PSS-terminated PEMs. After the thermal treatment, the odd-even effect becomes much weaker. Full article
Figures

Graphical abstract

Open AccessArticle Systematic Limitations in Concentration Analysis via Anomalous Small-Angle X-ray Scattering in the Small Structure Limit
Polymers 2016, 8(3), 85; https://doi.org/10.3390/polym8030085
Received: 10 February 2016 / Revised: 7 March 2016 / Accepted: 8 March 2016 / Published: 16 March 2016
Cited by 1 | PDF Full-text (2764 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb2+ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering [...] Read more.
Anomalous small angle scattering measurements have been applied to diluted solutions of anionic polyacrylates decorated by specifically-interacting Pb2+ cations, revealing partial collapse of the polyacrylate into pearl-like subdomains with a size on the order of a few nanometers. From the pure-resonant scattering contribution of the Pb2+ cations, and from subsequent analysis of the resonant-invariant, the amount of Pb2+ cations condensed onto the polyanions with respect to the total amount of Pb2+ cations in the solvent was estimated. In order to scrutinize systematic limitations in the determination of the chemical concentrations of resonant scattering counterions in the collapsed phase, Monte Carlo simulations have been performed. The simulations are based on structural confinements at variable size in the range of few nanometers, which represent the collapsed subdomains in the polyanions. These confinements were gradually filled to a high degree of the volume fraction with resonant scattering counterions giving access to a resonant-invariant at a variable degree of filling. The simulations revealed in the limit of small structures a significant underestimation of the true degree of filling of the collapsed subdomains when determining chemical concentrations of Pb2+ cations from the resonant invariant. Full article
Figures

Graphical abstract

Open AccessArticle Polyelectrolyte Threading through a Nanopore
Polymers 2016, 8(3), 73; https://doi.org/10.3390/polym8030073
Received: 23 January 2016 / Revised: 23 February 2016 / Accepted: 24 February 2016 / Published: 3 March 2016
Cited by 2 | PDF Full-text (6678 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time ⟨ τ ⟩ is shown to follow a scaling law Nα, and the exponent α increases monotonically from [...] Read more.
Threading charged polymers through a nanopore, driven by electric fields E, is investigated by means of Langevin dynamics simulations. The mean translocation time 〈 τ 〉 is shown to follow a scaling law Nα, and the exponent α increases monotonically from 1.16 (4) to 1.40 (3) with E. The result is double-checked by the calculation of mean square displacement of translocation coordinate, which asserts a scaling behavior tβ (for t near τ) with β complying with the relation αβ = 2. At a fixed chain length N, 〈τ〉 displayed a reciprocal scaling behavior E−1 in the weak and also in the strong fields, connected by a transition E−1.64(5) in the intermediate fields. The variations of the radius of gyration of chain and the positions of chain end are monitored during a translocation process; far-from-equilibrium behaviors are observed when the driving field is strong. A strong field can strip off the condensed ions on the chain when it passes the pore. The total charges of condensed ions are hence decreased. The studies for the probability and density distributions reveal that the monomers in the trans-region are gathered near the wall and form a pancake-like density profile with a hump cloud over it in the strong fields, due to fast translocation. Full article
Figures

Graphical abstract

Open AccessFeature PaperArticle pH-Responsive Intra- and Inter-Molecularly Micelle Formation of Anionic Diblock Copolymer in Water
Polymers 2016, 8(2), 56; https://doi.org/10.3390/polym8020056
Received: 25 January 2016 / Revised: 14 February 2016 / Accepted: 16 February 2016 / Published: 19 February 2016
PDF Full-text (2173 KB) | HTML Full-text | XML Full-text
Abstract
Poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-block-poly(sodium11-(acrylamido)undecanoate) (PAMPS–PAaU) was synthesized via reversible addition-fragmentation chain transfer (RAFT)-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (Mw/Mn = 1.23). The pH-induced association behavior [...] Read more.
Poly(sodium2-(acrylamido)-2-methylpropanesulfonate)-block-poly(sodium11-(acrylamido)undecanoate) (PAMPS–PAaU) was synthesized via reversible addition-fragmentation chain transfer (RAFT)-controlled radical polymerization. The “living” polymerization of PAaU was evidenced by the fact that the molecular weight distribution was narrow (Mw/Mn = 1.23). The pH-induced association behavior of PAMPS–PAaU in 0.1 M NaCl aqueous solutions as a function of solution pH was investigated by 1H NMR spin-spin relaxation time, dynamic light scattering (DLS), static light scattering (SLS), and fluorescence probe techniques. These results indicated that PAMPS–PAaU formed polymer micelles in 0.1 M NaCl aqueous solutions at pH < 9. At pH = 8–9, the polymer formed the micelles intramolecularly due to hydrophobic self-association of the PAaU block within the single polymer chain. On the other hand, at pH < 8, micellization occurred intermolecularly to form polymer micelles comprising hydrophobic PAaU cores and hydrophilic PAMPS shells. Full article
Figures

Graphical abstract

Open AccessArticle Conformation and Rheological Properties of Calf-Thymus DNA in Solution
Polymers 2016, 8(2), 51; https://doi.org/10.3390/polym8020051
Received: 7 January 2016 / Revised: 3 February 2016 / Accepted: 5 February 2016 / Published: 11 February 2016
Cited by 8 | PDF Full-text (6880 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Studies of DNA molecule behavior in aqueous solutions performed through different approaches allow assessment of the solute-solvent interactions and examination of the strong influence of conformation on its physicochemical properties, in the presence of different ionic species and ionic concentrations. Firstly, the conformational [...] Read more.
Studies of DNA molecule behavior in aqueous solutions performed through different approaches allow assessment of the solute-solvent interactions and examination of the strong influence of conformation on its physicochemical properties, in the presence of different ionic species and ionic concentrations. Firstly, the conformational behavior of calf-thymus DNA molecules in TE buffer solution is presented as a function of temperature. Secondly, their rheological behavior is discussed, as well as the evidence of the critical concentrations, i.e., the overlap and the entanglement concentrations (C* and Ce, respectively) from steady state flow and oscillatory dynamic shear experiments. The determination of the viscosity in the Newtonian plateau obtained from flow curves η ( ) allows estimation of the intrinsic viscosity and the specific viscosities at zero shear when C[η] < 40. At end, a generalized master curve is obtained from the variation of the specific viscosity as a function of the overlap parameter C[η]. The variation of the exponent s obtained from the power law η~ s for both flow and dynamic results is discussed in terms of Graessley’s analysis. In the semi-dilute regime with entanglements, a dynamic master curve is obtained as a function of DNA concentration (CDNA > 2.0 mg/mL) and temperature (10 °C < T < 40 °C). Full article
Figures

Graphical abstract

2015

Jump to: 2019, 2018, 2017, 2016, 2014, 2011, 2010

Open AccessReview Recent Progress and Perspectives in the Electrokinetic Characterization of Polyelectrolyte Films
Polymers 2016, 8(1), 7; https://doi.org/10.3390/polym8010007
Received: 2 December 2015 / Revised: 22 December 2015 / Accepted: 23 December 2015 / Published: 31 December 2015
Cited by 3 | PDF Full-text (1637 KB) | HTML Full-text | XML Full-text
Abstract
The analysis of the charge, structure and molecular interactions of/within polymeric substrates defines an important analytical challenge in materials science. Accordingly, advanced electrokinetic methods and theories have been developed to investigate the charging mechanisms and structure of soft material coatings. In particular, there [...] Read more.
The analysis of the charge, structure and molecular interactions of/within polymeric substrates defines an important analytical challenge in materials science. Accordingly, advanced electrokinetic methods and theories have been developed to investigate the charging mechanisms and structure of soft material coatings. In particular, there has been significant progress in the quantitative interpretation of streaming current and surface conductivity data of polymeric films from the application of recent theories developed for the electrohydrodynamics of diffuse soft planar interfaces. Here, we review the theory and experimental strategies to analyze the interrelations of the charge and structure of polyelectrolyte layers supported by planar carriers under electrokinetic conditions. To illustrate the options arising from these developments, we discuss experimental and simulation data for plasma-immobilized poly(acrylic acid) films and for a polyelectrolyte bilayer consisting of poly(ethylene imine) and poly(acrylic acid). Finally, we briefly outline potential future developments in the field of the electrokinetics of polyelectrolyte layers. Full article
Figures

Graphical abstract

2014

Jump to: 2019, 2018, 2017, 2016, 2015, 2011, 2010

Open AccessArticle Charge Inversion Effects in Electrophoresis of Polyelectrolytes in the Presence of Multivalent Counterions and Transversal Electric Fields
Polymers 2014, 6(12), 2942-2960; https://doi.org/10.3390/polym6122942
Received: 2 August 2014 / Revised: 14 November 2014 / Accepted: 20 November 2014 / Published: 4 December 2014
Cited by 1 | PDF Full-text (646 KB) | HTML Full-text | XML Full-text
Abstract
By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component [...] Read more.
By molecular dynamics simulations we investigate the transport of charged polymers in confinement, under externally applied electric fields, in straight cylinders of uniform diameter and in the presence of monovalent or multivalent counterions. The applied electric field has two components; a longitudinal component along the axis of the cylinder and a transversal component perpendicular to the cylinder axis. The direction of electrophoretic velocity depends on the polyelectrolyte length, valency of the counterions present in solution and transversal electric field value. A statistical model is put forward in order to explain these observations. Full article
Figures

Figure 1

Open AccessReview Polyelectrolyte Multilayers in Microfluidic Systems for Biological Applications
Polymers 2014, 6(8), 2100-2115; https://doi.org/10.3390/polym6082100
Received: 22 May 2014 / Revised: 15 July 2014 / Accepted: 22 July 2014 / Published: 31 July 2014
Cited by 7 | PDF Full-text (1351 KB) | HTML Full-text | XML Full-text
Abstract
The formation of polyelectrolyte multilayers (PEMs) for the first time, two decades ago, demonstrating the assembly on charged substrates in a very simple and efficient way, has proven to be a reliable method to obtain structures tunable at the nanometer scale. Much effort [...] Read more.
The formation of polyelectrolyte multilayers (PEMs) for the first time, two decades ago, demonstrating the assembly on charged substrates in a very simple and efficient way, has proven to be a reliable method to obtain structures tunable at the nanometer scale. Much effort has been put into the assembly of these structures for their use in biological applications. A number of these efforts have been in combination with microfluidic systems, which add to the nanoassembly that is already possible with polyelectrolytes, a new dimension in the construction of valuable structures, some of them not possible with conventional systems. This review focuses on the advancements demonstrated by the combination of PEMs and microfluidic systems, and their use in biological applications. Full article
Figures

Graphical abstract

Open AccessArticle Lipid Monolayers with Adsorbed Oppositely Charged Polyelectrolytes: Influence of Reduced Charge Densities
Polymers 2014, 6(7), 1999-2017; https://doi.org/10.3390/polym6071999
Received: 30 April 2014 / Revised: 26 June 2014 / Accepted: 27 June 2014 / Published: 10 July 2014
Cited by 2 | PDF Full-text (801 KB) | HTML Full-text | XML Full-text
Abstract
Polyelectrolytes in dilute solutions (0.01 mmol/L) adsorb in a two-dimensional lamellar phase to oppositely charged lipid monolayers at the air/water interface. The interchain separation is monitored by Grazing Incidence X-ray Diffraction. On monolayer compression, the interchain separation decreases to a factor of two. [...] Read more.
Polyelectrolytes in dilute solutions (0.01 mmol/L) adsorb in a two-dimensional lamellar phase to oppositely charged lipid monolayers at the air/water interface. The interchain separation is monitored by Grazing Incidence X-ray Diffraction. On monolayer compression, the interchain separation decreases to a factor of two. To investigate the influence of the electrostatic interaction, either the line charge density of the polymer is reduced (a statistic copolymer with 90% and 50% charged monomers) or mixtures between charged and uncharged lipids are used (dipalmitoylphosphatidylcholine (DPPC)/ dioctadecyldimethylammonium bromide (DODAB)) On decrease of the surface charge density, the interchain separation increases, while on decrease of the linear charge density, the interchain separation decreases. The ratio between charged monomers and charged lipid molecules is fairly constant; it decreases up to 30% when the lipids are in the fluid phase. With decreasing surface charge or linear charge density, the correlation length of the lamellar order decreases. Full article
Figures

Graphical abstract

Open AccessArticle Salt Effect on Osmotic Pressure of Polyelectrolyte Solutions: Simulation Study
Polymers 2014, 6(7), 1897-1913; https://doi.org/10.3390/polym6071897
Received: 21 March 2014 / Revised: 24 June 2014 / Accepted: 26 June 2014 / Published: 4 July 2014
Cited by 11 | PDF Full-text (1079 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Abstract: We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo [...] Read more.
Abstract: We present results of the hybrid Monte Carlo/molecular dynamics simulations of the osmotic pressure of salt solutions of polyelectrolytes. In our simulations, we used a coarse-grained representation of polyelectrolyte chains, counterions and salt ions. During simulation runs, we alternate Monte Carlo and molecular dynamics simulation steps. Monte Carlo steps were used to perform small ion exchange between simulation box containing salt ions (salt reservoir) and simulation box with polyelectrolyte chains, counterions and salt ions (polyelectrolyte solution). This allowed us to model Donnan equilibrium and partitioning of salt and counterions across membrane impermeable to polyelectrolyte chains. Our simulations have shown that the main contribution to the system osmotic pressure is due to salt ions and osmotically active counterions. The fraction of the condensed (osmotically inactive) counterions first increases with decreases in the solution ionic strength then it saturates. The reduced value of the system osmotic coefficient is a universal function of the ratio of the concentration of osmotically active counterions and salt concentration in salt reservoir. Simulation results are in a very good agreement with osmotic pressure measurements in sodium polystyrene sulfonate, DNA, polyacrylic acid, sodium polyanetholesulfonic acid, polyvinylbenzoic acid, and polydiallyldimethylammonium chloride solutions. Full article
Figures

Figure 1

Open AccessArticle Stimuli-Responsive Polyelectrolyte Brushes As a Matrix for the Attachment of Gold Nanoparticles: The Effect of Brush Thickness on Particle Distribution
Polymers 2014, 6(7), 1877-1896; https://doi.org/10.3390/polym6071877
Received: 16 April 2014 / Revised: 23 June 2014 / Accepted: 24 June 2014 / Published: 27 June 2014
Cited by 24 | PDF Full-text (1259 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The effect of brush thickness on the loading of gold nanoparticles (AuNPs) within stimuli-responsive poly-(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) polyelectrolyte brushes is reported. Atom transfer radical polymerization (ATRP) was used to grow polymer brushes via a “grafting from” approach. The brush thickness was tuned [...] Read more.
The effect of brush thickness on the loading of gold nanoparticles (AuNPs) within stimuli-responsive poly-(N,N-(dimethylamino ethyl) methacrylate) (PDMAEMA) polyelectrolyte brushes is reported. Atom transfer radical polymerization (ATRP) was used to grow polymer brushes via a “grafting from” approach. The brush thickness was tuned by varying the polymerization time. Using a new type of sealed reactor, thick brushes were synthesized. A systematic study was performed by varying a single parameter (brush thickness), while keeping all other parameters constant. AuNPs of 13 nm in diameter were attached by incubation. X-ray reflectivity, electron scanning microscopy and ellipsometry were used to study the particle loading, particle distribution and interpenetration of the particles within the brush matrix. A model for the structure of the brush/particle hybrids was derived. The particle number densities of attached AuNPs depend on the brush thickness, as do the optical properties of the hybrids. An increasing particle number density was found for increasing brush thickness, due to an increased surface roughness. Full article
Figures

Graphical abstract

Open AccessArticle The Effect of Salt on the Complex Coacervation of Vinyl Polyelectrolytes
Polymers 2014, 6(6), 1756-1772; https://doi.org/10.3390/polym6061756
Received: 5 May 2014 / Revised: 3 June 2014 / Accepted: 4 June 2014 / Published: 16 June 2014
Cited by 79 | PDF Full-text (1785 KB) | HTML Full-text | XML Full-text
Abstract
Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation [...] Read more.
Complex coacervation is an electrostatically-driven phase separation phenomenon that is utilized in a wide range of everyday applications and is of great interest for the creation of self-assembled materials. Here, we utilized turbidity to characterize the effect of salt type on coacervate formation using two vinyl polyelectrolytes, poly(acrylic acid sodium salt) (pAA) and poly(allylamine hydrochloride) (pAH), as simple models for industrial and biological coacervates. We confirmed the dominant role of salt valence on the extent of coacervate formation, while demonstrating the presence of significant secondary effects, which can be described by Hofmeister-like behavior. These results revealed the importance of ion-specific interactions, which are crucial for the informed design of coacervate-based materials for use in complex ionic environments, and can enable more detailed theoretical investigations on the role of subtle electrostatic and thermodynamic effects in complex coacervation. Full article
Figures

Graphical abstract

Open AccessArticle A Coarse-Grained DNA Model Parameterized from Atomistic Simulations by Inverse Monte Carlo
Polymers 2014, 6(6), 1655-1675; https://doi.org/10.3390/polym6061655
Received: 15 April 2014 / Revised: 15 May 2014 / Accepted: 18 May 2014 / Published: 30 May 2014
Cited by 28 | PDF Full-text (815 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Computer modeling of very large biomolecular systems, such as long DNA polyelectrolytes or protein-DNA complex-like chromatin cannot reach all-atom resolution in a foreseeable future and this necessitates the development of coarse-grained (CG) approximations. DNA is both highly charged and mechanically rigid semi-flexible polymer [...] Read more.
Computer modeling of very large biomolecular systems, such as long DNA polyelectrolytes or protein-DNA complex-like chromatin cannot reach all-atom resolution in a foreseeable future and this necessitates the development of coarse-grained (CG) approximations. DNA is both highly charged and mechanically rigid semi-flexible polymer and adequate DNA modeling requires a correct description of both its structural stiffness and salt-dependent electrostatic forces. Here, we present a novel CG model of DNA that approximates the DNA polymer as a chain of 5-bead units. Each unit represents two DNA base pairs with one central bead for bases and pentose moieties and four others for phosphate groups. Charges, intra- and inter-molecular force field potentials for the CG DNA model were calculated using the inverse Monte Carlo method from all atom molecular dynamic (MD) simulations of 22 bp DNA oligonucleotides. The CG model was tested by performing dielectric continuum Langevin MD simulations of a 200 bp double helix DNA in solutions of monovalent salt with explicit ions. Excellent agreement with experimental data was obtained for the dependence of the DNA persistent length on salt concentration in the range 0.1–100 mM. The new CG DNA model is suitable for modeling various biomolecular systems with adequate description of electrostatic and mechanical properties. Full article
Figures

Graphical abstract

Open AccessArticle Development of a Biocompatible Layer-by-Layer Film System Using Aptamer Technology for Smart Material Applications
Polymers 2014, 6(5), 1631-1654; https://doi.org/10.3390/polym6051631
Received: 17 March 2014 / Revised: 4 May 2014 / Accepted: 8 May 2014 / Published: 23 May 2014
Cited by 9 | PDF Full-text (2854 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Aptamers are short, single-stranded nucleic acids that fold into well-defined three dimensional (3D) structures that allow for binding to a target molecule with affinities and specificities that can rival or in some cases exceed those of antibodies. The compatibility of aptamers with nanostructures [...] Read more.
Aptamers are short, single-stranded nucleic acids that fold into well-defined three dimensional (3D) structures that allow for binding to a target molecule with affinities and specificities that can rival or in some cases exceed those of antibodies. The compatibility of aptamers with nanostructures such as thin films, in combination with their affinity, selectivity, and conformational changes upon target interaction, could set the foundation for the development of novel smart materials. In this study, the development of a biocompatible aptamer-polyelectrolyte film system was investigated using a layer-by-layer approach. Using fluorescence microscopy, we demonstrated the ability of the sulforhodamine B aptamer to bind its cognate target while sequestered in a chitosan-hyaluronan film matrix. Studies using Ultraviolet-visible (UV-Vis) spectrophotometry also suggest that deposition conditions such as rinsing time and volume play a strong role in the internal film interactions and growth mechanisms of chitosan-hyaluronan films. The continued study and development of aptamer-functionalized thin films provides endless new opportunities for novel smart materials and has the potential to revolutionize the field of controlled release. Full article
Figures

Graphical abstract

Open AccessArticle Structure of Microgels with Debye–Hückel Interactions
Polymers 2014, 6(5), 1602-1617; https://doi.org/10.3390/polym6051602
Received: 31 March 2014 / Revised: 13 May 2014 / Accepted: 19 May 2014 / Published: 23 May 2014
Cited by 29 | PDF Full-text (1089 KB) | HTML Full-text | XML Full-text
Abstract
The structural properties of model microgel particles are investigated by molecular dynamics simulations applying a coarse-grained model. A microgel is comprised of a regular network of polymers internally connected by tetra-functional cross-links and with dangling ends at its surface. The self-avoiding polymers are [...] Read more.
The structural properties of model microgel particles are investigated by molecular dynamics simulations applying a coarse-grained model. A microgel is comprised of a regular network of polymers internally connected by tetra-functional cross-links and with dangling ends at its surface. The self-avoiding polymers are modeled as bead-spring linear chains. Electrostatic interactions are taken into account by the Debye–Hückel potential. The microgels exhibit a quite uniform density under bad solvent conditions with a rather sharp surface. With increasing Debye length, structural inhomogeneities appear, their surface becomes fuzzy and, at very large Debye lengths, well defined again. Similarly, the polymer conformations change from a self-avoiding walk to a rod-like behavior. Thereby, the average polymer radius of gyration follows a scaling curve in terms of polymer length and persistence length, with an asymptotic rod-like behavior for swollen microgels and self-avoiding walk behavior for weakly swollen gel particles. Full article
Figures

Graphical abstract

Open AccessReview Structures and Synthesis of Zwitterionic Polymers
Polymers 2014, 6(5), 1544-1601; https://doi.org/10.3390/polym6051544
Received: 16 April 2014 / Revised: 3 May 2014 / Accepted: 8 May 2014 / Published: 23 May 2014
Cited by 121 | PDF Full-text (463 KB) | HTML Full-text | XML Full-text
Abstract
The structures and synthesis of polyzwitterions (“polybetaines”) are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus [...] Read more.
The structures and synthesis of polyzwitterions (“polybetaines”) are reviewed, emphasizing the literature of the past decade. Particular attention is given to the general challenges faced, and to successful strategies to obtain polymers with a true balance of permanent cationic and anionic groups, thus resulting in an overall zero charge. Also, the progress due to applying new methodologies from general polymer synthesis, such as controlled polymerization methods or the use of “click” chemical reactions is presented. Furthermore, the emerging topic of responsive (“smart”) polyzwitterions is addressed. The considerations and critical discussions are illustrated by typical examples. Full article
Figures

Graphical abstract

Open AccessArticle pH and Salt Effects on the Associative Phase Separation of Oppositely Charged Polyelectrolytes
Polymers 2014, 6(5), 1414-1436; https://doi.org/10.3390/polym6051414
Received: 27 March 2014 / Revised: 9 May 2014 / Accepted: 9 May 2014 / Published: 16 May 2014
Cited by 40 | PDF Full-text (3356 KB) | HTML Full-text | XML Full-text
Abstract
The classical Voorn-Overbeek thermodynamic theory of complexation and phase separation of oppositely charged polyelectrolytes is generalized to account for the charge accessibility and hydrophobicity of polyions, size of salt ions, and pH variations. Theoretical predictions of the effects of pH and salt concentration [...] Read more.
The classical Voorn-Overbeek thermodynamic theory of complexation and phase separation of oppositely charged polyelectrolytes is generalized to account for the charge accessibility and hydrophobicity of polyions, size of salt ions, and pH variations. Theoretical predictions of the effects of pH and salt concentration are compared with published experimental data and experiments we performed, on systems containing poly(acrylic acid) (PAA) as the polyacid and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) or poly(diallyldimethyl ammonium chloride) (PDADMAC) as the polybase. In general, the critical salt concentration below which the mixture phase separates, increases with degree of ionization and with the hydrophobicity of polyelectrolytes. We find experimentally that as the pH is decreased below 7, and PAA monomers are neutralized, the critical salt concentration increases, while the reverse occurs when pH is raised above 7. We predict this asymmetry theoretically by introducing a large positive Flory parameter (= 0.75) for the interaction of neutral PAA monomers with water. This large positive Flory parameter is supported by molecular dynamics simulations, which show much weaker hydrogen bonding between neutral PAA and water than between charged PAA and water, while neutral and charged PDMAEMA show similar numbers of hydrogen bonds. This increased hydrophobicity of neutral PAA at reduced pH increases the tendency towards phase separation despite the reduction in charge interactions between the polyelectrolytes. Water content and volume of coacervate are found to be a strong function of the pH and salt concentration. Full article
Figures

Figure 1

Open AccessReview Does Electrical Conductivity of Linear Polyelectrolytes in Aqueous Solutions Follow the Dynamic Scaling Laws? A Critical Review and a Summary of the Key Relations
Polymers 2014, 6(4), 1207-1231; https://doi.org/10.3390/polym6041207
Received: 14 February 2014 / Revised: 4 April 2014 / Accepted: 11 April 2014 / Published: 22 April 2014
Cited by 6 | PDF Full-text (660 KB) | HTML Full-text | XML Full-text
Abstract
In this review, we focus on the electrical conductivity of aqueous polyelectrolyte solutions in the light of the dynamic scaling laws, recently proposed by Dobrynin and Rubinstein, to take into account the polymer conformations in different concentration regimes, both in good and poor [...] Read more.
In this review, we focus on the electrical conductivity of aqueous polyelectrolyte solutions in the light of the dynamic scaling laws, recently proposed by Dobrynin and Rubinstein, to take into account the polymer conformations in different concentration regimes, both in good and poor solvent conditions. This approach allows us to separate contributions due to polymer conformation from those due to the ionic character of the chain, and offers the possibility to extend the validity of the Manning conductivity model to dilute and semidilute regimes. The electrical conductivity in the light of the scaling approach compares reasonably well with the observed values for different polyelectrolytes in aqueous solutions, over an extended concentration range, from the dilute to the semidilute regime. Full article
Figures

Figure 1

2011

Jump to: 2019, 2018, 2017, 2016, 2015, 2014, 2010

Open AccessArticle Behavior of Na+-Polystyrene Sulfonate at the Interface with Single-Walled Carbon Nanotubes (SWNTs) and Its Implication to SWNT Suspension Stability
Polymers 2011, 3(2), 942-954; https://doi.org/10.3390/polym3020942
Received: 16 May 2011 / Accepted: 12 June 2011 / Published: 14 June 2011
Cited by 11 | PDF Full-text (813 KB) | HTML Full-text | XML Full-text
Abstract
The assembly of sodium polystyrene sulfonate (Na+-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation [...] Read more.
The assembly of sodium polystyrene sulfonate (Na+-PSS) at the surface of single-walled carbon nanotubes (SWNTs) in pH 3 aqueous solution is described. Rather than forming linear or sheet-like chain morphologies over SWNT surfaces, Na+-PSS adopts a spherically collapsed conformation believed to be the result of cation (either Na+ or H+) condensation onto the ionized polymer chain. It is well reported that cations (and also anions) adsorb preferentially onto single-walled and multi-walled carbon nanotube surfaces leading to an increased ion concentration in the near surface regions relative to the bulk solution. This work provides experimental evidence for preferentially absorbed cation condensation onto PSS anions until those cations are spaced at distances corresponding to the Bjerrum length ( B), as defined by the Manning theory of ion condensation, at the SWNT surface. The resulting electrostearic repulsions allow the SWNTs to remain suspended for days. Furthermore , coulombic repulsion among SWNT bundles after cation adsorption alone is not sufficient to form stable suspensions—but rather the stearic repulsions associated with spherically collapsed PSS at the nanotube surface is responsible for suspension stability. It is believed that the ultrasonic agitation drives cations into the small spaces between SWNT bundles and coulombic potential attracts the PSS to those regions. Full article
Open AccessArticle Using Light Scattering to Screen Polyelectrolytes (PEL) Performance in Flocculation
Polymers 2011, 3(2), 915-927; https://doi.org/10.3390/polym3020915
Received: 27 April 2011 / Accepted: 23 May 2011 / Published: 27 May 2011
Cited by 12 | PDF Full-text (334 KB) | HTML Full-text | XML Full-text
Abstract
Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the [...] Read more.
Flocculation of precipitated calcium carbonate (PCC) was monitored using light diffraction spectroscopy (LDS). Four cationic polyacrylamides of high molar mass and with different degrees of branching, all copolymers of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (Q9), were tested. LDS supplied information about the kinetic curves for flocs growth and also for the flocs structure evolution. Flocculation kinetics, flocs size and structure, flocs resistance and reflocculation capacity could be correlated with the degree of branching of the polyelectrolytes (PEL). Furthermore, PEL with different degrees of branching corresponded to different values for the intrinsic viscosity, indicating differences in the polymer conformation, which explained well the performance differences in flocculation. Full article
Figures

Graphical abstract

Open AccessArticle Counterion Condensation and Effective Charge of PAMAM Dendrimers
Polymers 2011, 3(2), 812-819; https://doi.org/10.3390/polym3020812
Received: 24 March 2011 / Accepted: 14 April 2011 / Published: 27 April 2011
Cited by 15 | PDF Full-text (359 KB) | HTML Full-text | XML Full-text
Abstract
PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino [...] Read more.
PAMAM dendrimers are used as a model system to investigate the effects of counterion condensation and the effective charge for spherical polyelectrolytes. Because of their amino groups, PAMAM dendrimers are weak polyelectrolytes. Lowering the pH results in an increasing protonation of the amino groups which is monitored via the proton chemical shifts of the adjacent CH2 groups. The effective charge is determined from a combination of diffusion and electrophoresis NMR. The fraction of the charges, which are effective for the interaction with an external electric field or other charges, decreases with increasing generation (size) of the dendrimers. Full article
Figures

Graphical abstract

Open AccessArticle Polyelectrolyte Complex Nanoparticles of Poly(ethyleneimine) and Poly(acrylic acid): Preparation and Applications
Polymers 2011, 3(2), 762-778; https://doi.org/10.3390/polym3020762
Received: 28 February 2011 / Accepted: 29 March 2011 / Published: 12 April 2011
Cited by 25 | PDF Full-text (530 KB) | HTML Full-text | XML Full-text
Abstract
In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, [...] Read more.
In this contribution we outline polyelectrolyte (PEL) complex (PEC) nanoparticles, prepared by mixing solutions of the low cost PEL components poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC). It was found, that the size and internal structure of PEI/PAC particles can be regulated by process, media and structural parameters. Especially, mixing order, mixing ratio, PEL concentration, pH and molecular weight, were found to be sensible parameters to regulate the size (diameter) of spherical PEI/PAC nanoparticles, in the range between 80–1,000 nm, in a defined way. Finally, applications of dispersed PEI/PAC particles as additives for the paper making process, as well as for drug delivery, are outlined. PEI/PAC nanoparticles mixed directly on model cellulose film showed a higher adsorption level applying the mixing order 1. PAC 2. PEI compared to 1. PEI 2. PAC. Surface bound PEI/PAC nanoparticles were found to release a model drug compound and to stay immobilized due to the contact with the aqueous release medium. Full article
Open AccessArticle Phase Diagrams of the Aqueous Two-Phase Systems of Poly(ethylene glycol)/Sodium Polyacrylate/Salts
Polymers 2011, 3(1), 587-601; https://doi.org/10.3390/polym3010587
Received: 15 February 2011 / Accepted: 7 March 2011 / Published: 9 March 2011
Cited by 29 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text
Abstract
Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na2SO4, sodium adipate and sodium azelate) and salt concentrations on the position of [...] Read more.
Aqueous two-phase systems consisting of polyethylene glycol (PEG), sodium polyacrylate (NaPAA), and a salt have been studied. The effects of the polymer size, salt type (NaCl, Na2SO4, sodium adipate and sodium azelate) and salt concentrations on the position of the binodal curve were investigated. The investigated PEG molecules had a molar mass of 2,000 to 8,000 g/mol, while that of NaPAA was 8,000 g/mol. Experimental phase diagrams, and tie lines and calculated phase diagrams, based on Flory-Huggins theory of polymer solutions are presented. Due to strong enthalpic and entropic balancing forces, the hydrophobicity of the added salt has a strong influence on the position of the binodal, which could be reproduced by model calculations. Full article

2010

Jump to: 2019, 2018, 2017, 2016, 2015, 2014, 2011

Open AccessArticle Polyelectrolytes: Influence on Evaporative Self-Assembly of Particles and Assembly of Multilayers with Polymers, Nanoparticles and Carbon Nanotubes
Polymers 2010, 2(4), 690-708; https://doi.org/10.3390/polym2040690
Received: 14 October 2010 / Revised: 19 November 2010 / Accepted: 6 December 2010 / Published: 9 December 2010
Cited by 5 | PDF Full-text (3974 KB) | HTML Full-text | XML Full-text
Abstract
Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte [...] Read more.
Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte multilayer coatings bring multifunctionality to spherical particles and planar films. Studying the construction of polyelectrolyte assemblies is convenient in the planar layout: it is reported here for incorporation of gold and magnetic nanoparticles as well as of carbon nanotubes. Gold nanoparticles concentration is controlled within the films. Potential applications of both spherical structures and planar films are highlighted. Full article
Figures

Figure 1

Open AccessArticle Glucan Particle Encapsulated Rifampicin for Targeted Delivery to Macrophages