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Polymers, Volume 9, Issue 8 (August 2017)

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Cover Story (view full-size image) Threadings are architecture-specific topological constraints that give rise to complex and [...] Read more.
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Open AccessReview
Characterization of Cell Scaffolds by Atomic Force Microscopy
Polymers 2017, 9(8), 383; https://doi.org/10.3390/polym9080383
Received: 30 July 2017 / Revised: 13 August 2017 / Accepted: 16 August 2017 / Published: 21 August 2017
Cited by 3 | Viewed by 2241 | PDF Full-text (1581 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This review reports on the use of the atomic force microscopy (AFM) in the investigation of cell scaffolds in recent years. It is shown how the technique is able to deliver information about the scaffold surface properties (e.g., topography), as well as about [...] Read more.
This review reports on the use of the atomic force microscopy (AFM) in the investigation of cell scaffolds in recent years. It is shown how the technique is able to deliver information about the scaffold surface properties (e.g., topography), as well as about its mechanical behavior (Young’s modulus, viscosity, and adhesion). In addition, this short review also points out the utilization of the atomic force microscope technique beyond its usual employment in order to investigate another type of basic questions related to materials physics, chemistry, and biology. The final section discusses in detail the novel uses that those alternative measuring modes can bring to this field in the future. Full article
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Open AccessRetraction
Retraction: Abdalla, S., et al. A Bio Polymeric Adhesive Produced by Photo Cross-Linkable Technique. Polymers 2016, 8, 292, doi:10.3390/polym8080292 and Abdalla, S., et al. Controlled Light Cross-Linking Technique to Prepare Healable Materials. Polymers 2017, 9, 241, doi:10.3390/polym9060241
Polymers 2017, 9(8), 382; https://doi.org/10.3390/polym9080382
Received: 17 August 2017 / Revised: 17 August 2017 / Accepted: 17 August 2017 / Published: 21 August 2017
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Abstract
These two articles [1,2] published in Polymers will be marked as retracted.[...] Full article
Open AccessArticle
Light-Driven Liquid Crystal Circular Dammann Grating Fabricated by a Micro-Patterned Liquid Crystal Polymer Phase Mask
Polymers 2017, 9(8), 380; https://doi.org/10.3390/polym9080380
Received: 27 June 2017 / Revised: 11 August 2017 / Accepted: 17 August 2017 / Published: 21 August 2017
Cited by 3 | Viewed by 2009 | PDF Full-text (1413 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports [...] Read more.
As one of the diffractive optical elements, circular Dammann grating has shown its excellent versatility in practical applications. The electrically switchable Dammann grating has been extensively investigated; however, the research on the optically tunable circular Dammann grating has received less attention and reports on this subject have been insufficient in the past decade. In this paper, three-order and eight-order binary-phase liquid crystal circular Dammann gratings with two mutually orthogonal photo-induced alignments in every two adjacent alignment domains, fabricated by a micro-patterned liquid crystal polymer phase mask, are proposed to generate annular uniform-intensity patterns in the far field. A simple maskless optical tuning of an eight-order liquid crystal circular Dammann grating is demonstrated by controlling the polarization of an ultraviolet light as well as the energy dose. The proposed liquid crystal circular Dammann gratings with high efficiencies and desirable uniformities exhibit outstanding optical as well as electrical tunabilities, enabling the widespread prospective applications in adaptive photonic chips stimulated flexibly by only light or by the combination of light and electric field. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Increased X-ray Visualization of Shape Memory Polymer Foams by Chemical Incorporation of Iodine Motifs
Polymers 2017, 9(8), 381; https://doi.org/10.3390/polym9080381
Received: 3 August 2017 / Revised: 18 August 2017 / Accepted: 18 August 2017 / Published: 20 August 2017
Cited by 1 | Viewed by 2240 | PDF Full-text (4203 KB) | HTML Full-text | XML Full-text
Abstract
Shape memory polymers can be programmed into a secondary geometry and recovered to their primary geometry with the application of a controlled stimulus. Porous shape memory polymer foam scaffolds that respond to body temperature show particular promise for embolic medical applications. A limitation [...] Read more.
Shape memory polymers can be programmed into a secondary geometry and recovered to their primary geometry with the application of a controlled stimulus. Porous shape memory polymer foam scaffolds that respond to body temperature show particular promise for embolic medical applications. A limitation for the minimally invasive delivery of these materials is an inherent lack of X-ray contrast. In this work, a triiodobenzene containing a monomer was incorporated into a shape memory polymer foam material system to chemically impart X-ray visibility and increase material toughness. Composition and process changes enabled further control over material density and thermomechanical properties. The proposed material system demonstrates a wide range of tailorable functional properties for the design of embolic medical devices, including X-ray visibility, expansion rate, and porosity. Enhanced visualization of these materials can improve the acute performance of medical devices used to treat vascular malformations, and the material porosity provides a healing scaffold for durable occlusion. Full article
(This article belongs to the Special Issue Shape Memory Polymers)
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Open AccessArticle
The Effect of Network Solvation on the Viscoelastic Response of Polymer Hydrogels
Polymers 2017, 9(8), 379; https://doi.org/10.3390/polym9080379
Received: 29 June 2017 / Revised: 11 August 2017 / Accepted: 15 August 2017 / Published: 19 August 2017
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Abstract
The majority of investigations consider the deformation response of hydrogels, fully controlled by the deformation behavior of their polymer network, neglecting the contribution caused by the presence of water. Here, we use molecular dynamics simulation in an attempt to include the effect of [...] Read more.
The majority of investigations consider the deformation response of hydrogels, fully controlled by the deformation behavior of their polymer network, neglecting the contribution caused by the presence of water. Here, we use molecular dynamics simulation in an attempt to include the effect of physically bound water via polymer chain solvation on the viscoelastic response of hydrogels. Our model allows us to control the solvation of chains as an independent variable. The solvation of the chain is independent of other factors, mainly the effect (pH) which interferes significantly in experiments. The solvation of hydrophilic chains was controlled by setting a partial charge on the chains and quantified by the Bjerrum length (BL). The BL was calculated from the partial electric charge of the solvent and macromolecular network. When the BL is short, the repulsive Van der Waals interactions are predominant in the vicinity of macromolecules and solvation is not observed. For a long BL, the water molecules in the solvation zone of network are in the same range as attractive intermolecular forces and the solvation occurs. The model also allows the consideration of molecules of water attached to two chains simultaneously, forming a temporary bridging. By elucidating the relations between solvation of the network and structural changes during the network deformation, one may predict the viscoelastic properties of hydrogels knowing the molecular structure of its polymer chains. Full article
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Open AccessArticle
Mechanical Properties of Composite Hydrogels of Alginate and Cellulose Nanofibrils
Polymers 2017, 9(8), 378; https://doi.org/10.3390/polym9080378
Received: 27 June 2017 / Revised: 10 August 2017 / Accepted: 17 August 2017 / Published: 19 August 2017
Cited by 10 | Viewed by 2390 | PDF Full-text (9988 KB) | HTML Full-text | XML Full-text
Abstract
Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan [...] Read more.
Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering. Full article
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Open AccessArticle
Effect of Sodium Hydroxide Treatments on the Tensile Strength and the Interphase Quality of Hemp Core Fiber-Reinforced Polypropylene Composites
Polymers 2017, 9(8), 377; https://doi.org/10.3390/polym9080377
Received: 21 July 2017 / Revised: 11 August 2017 / Accepted: 14 August 2017 / Published: 19 August 2017
Cited by 4 | Viewed by 2173 | PDF Full-text (3144 KB) | HTML Full-text | XML Full-text
Abstract
The formulation of greener composite materials by substituting glass fibers with natural fibers is a current field of research. If such natural fiber reinforcements come from industrial side streams, as hemp core fibers (HCFs) come from the extraction of hemp strands for the [...] Read more.
The formulation of greener composite materials by substituting glass fibers with natural fibers is a current field of research. If such natural fiber reinforcements come from industrial side streams, as hemp core fibers (HCFs) come from the extraction of hemp strands for the textile industry, an additional advantage can be identified. Nonetheless, such by-product fibers show some drawbacks, such as high lignin contents, which can make it difficult to obtain a good interphase between the fibers and the matrix and to obtain a good fiber individualization. A digestion treatment at different NaOH contents is proposed to eliminate soluble lignin and extractives from the surface of the fibers. At the same time, the use of a coupling agent solves incompatibilities between the fibers and the matrix. The composites were tensile tested and the impact of the proposed treatments is evaluated and discussed. Later, the Kelly-Tyson modified equation and a modified rule of mixtures—the micro-mechanic models—is used to study the impact of such treatments on the quality of the interphase between the polymer and the reinforcement. Both treatments showed a high impact on the tensile strength and the quality of the interphase, obtaining competitive composite materials reinforced with HCFs derived from a by-product. Full article
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Open AccessArticle
Effect of Catechol Content in Catechol-Conjugated Dextrans on Antiplatelet Performance
Polymers 2017, 9(8), 376; https://doi.org/10.3390/polym9080376
Received: 26 June 2017 / Revised: 17 August 2017 / Accepted: 17 August 2017 / Published: 19 August 2017
Cited by 1 | Viewed by 1862 | PDF Full-text (1820 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The surface coating of solid substrates using dextrans has gained a great deal of attention, because dextran-coated surfaces show excellent anti-fouling property as well as biocompatibility behavior. Much effort has been made to develop efficient methods for grafting dextrans on solid surfaces. This [...] Read more.
The surface coating of solid substrates using dextrans has gained a great deal of attention, because dextran-coated surfaces show excellent anti-fouling property as well as biocompatibility behavior. Much effort has been made to develop efficient methods for grafting dextrans on solid surfaces. This led to the development of catechol-conjugated dextrans (Dex-C) which can adhere to a number of solid surfaces, inspired by the underwater adhesion behavior of marine mussels. The present study is a systematic investigation of the characteristics of surface coatings developed with Dex-C. Various Dex-C with different catechol contents were synthesized and used as a surface coating material. The effect of catechol content on surface coating and antiplatelet performance was investigated. Full article
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Open AccessArticle
Correlation-Based Multiplexing of Complex Amplitude Data Pages in a Holographic Storage System Using Digital Holographic Techniques
Polymers 2017, 9(8), 375; https://doi.org/10.3390/polym9080375
Received: 30 June 2017 / Revised: 9 August 2017 / Accepted: 15 August 2017 / Published: 18 August 2017
Cited by 2 | Viewed by 1548 | PDF Full-text (2769 KB) | HTML Full-text | XML Full-text
Abstract
Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. [...] Read more.
Holographic recording media can store the amplitude and the phase, or the complex amplitude, of a beam on the basis of holography. Owing to this characteristic, digital data can be encoded onto the complex amplitude of a signal beam in holographic data storage. However, most of conventional holographic storage systems encode digital data onto the amplitude alone because there are difficulties for modulating and detecting the phase. To solve the difficulties, a holographic storage system using digital holographic techniques has been proposed. With the help of digital holographic techniques, it is possible to modulate and detect the complex amplitude of a signal beam. Moreover, the proposed system can modulate the complex amplitude of a reference beam. In this paper, by making use of the capability, a correlation-based multiplexing with uncorrelated reference beams is demonstrated in the proposed system. Multiple holograms can be recorded in the same volume of a recording medium with no need for mechanical movements. Experimental results show that the proposed system with a correlation-based multiplexing can improve the storage capacity and can utilize the full potential of a recording medium without crosstalk noise stem from the optical setup. Full article
(This article belongs to the Special Issue Photo-Responsive Polymers)
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Open AccessArticle
Bacterial Nanocellulose from Side-Streams of Kombucha Beverages Production: Preparation and Physical-Chemical Properties
Polymers 2017, 9(8), 374; https://doi.org/10.3390/polym9080374
Received: 15 July 2017 / Revised: 11 August 2017 / Accepted: 14 August 2017 / Published: 18 August 2017
Cited by 5 | Viewed by 3536 | PDF Full-text (8197 KB) | HTML Full-text | XML Full-text
Abstract
We focused on preparing cellulose nanofibrils by purification, separation, and mechanical treatment of Kombucha membranes (KM) resulted as secondary product from beverage production by fermentation of tea broth with symbiotic culture of bacteria and yeast (SCOBY). We purified KM using two alkaline solutions, [...] Read more.
We focused on preparing cellulose nanofibrils by purification, separation, and mechanical treatment of Kombucha membranes (KM) resulted as secondary product from beverage production by fermentation of tea broth with symbiotic culture of bacteria and yeast (SCOBY). We purified KM using two alkaline solutions, 1 and 4 M NaOH, which afterwards were subjected to various mechanical treatments. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) were employed to evaluate the purification degree, the size and aspect of cellulose fibrils after each treatment step, the physical-chemical properties of intermediary and final product, and for comparison with micro-crystalline cellulose from wooden sources. We determined that 1 M NaOH solution leads to approx. 85% purification, while a higher concentration assures almost 97% impurities removal. XRD analysis evidenced an increase in crystallinity from 37% to 87% after purification, the characteristic diffractograms of Iα and Iβ cellulose allomorphs, and a further decrease in crystallinity to 46% after microfluidization, fact correlated with a drastically decrease in fibrils’ size. FTIR analysis evidenced the appearance of new chain ends by specific transmission bands at 2941 and 2843cm−1. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessCommunication
Synthesis of Humin-Phenol-Formaldehyde Adhesive
Polymers 2017, 9(8), 373; https://doi.org/10.3390/polym9080373
Received: 27 May 2017 / Revised: 11 August 2017 / Accepted: 14 August 2017 / Published: 18 August 2017
Cited by 7 | Viewed by 2247 | PDF Full-text (2289 KB) | HTML Full-text | XML Full-text
Abstract
Humins are low-value-added byproducts from the biomass acid hydrolysis process. In the present work, humins were first employed as a phenol replacement for synthesis of modified phenol-formaldehyde adhesives through a two-step process. In this process, humins were first utilized to obtain alkaline soluble [...] Read more.
Humins are low-value-added byproducts from the biomass acid hydrolysis process. In the present work, humins were first employed as a phenol replacement for synthesis of modified phenol-formaldehyde adhesives through a two-step process. In this process, humins were first utilized to obtain alkaline soluble products, mainly consisting of phenolics, through a hydrothermal process. The obtained alkaline soluble products then reacted with phenol and formaldehyde to produce humin-phenol-formaldehyde adhesive (HPFA). The physicochemical properties of HPFA, including viscosity, bonding strength, pH, free formaldehyde level, free phenol level and solid content, met the requirements of the GB/T 14732-2006 Chinese National Standard. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessArticle
Microstructural and Mechanical Implications of Microscaled Assembly in Droplet-based Multi-Material Additive Manufacturing
Polymers 2017, 9(8), 372; https://doi.org/10.3390/polym9080372
Received: 30 June 2017 / Revised: 15 August 2017 / Accepted: 16 August 2017 / Published: 18 August 2017
Cited by 6 | Viewed by 2484 | PDF Full-text (11670 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
To reveal the potential and limits of multi-material three-dimensional (3D) printed parts in droplet-based additive manufacturing, a study combining tensile experiments and 3D imaging technique is proposed. A polymeric composite structure made of acrylonitrile butadiene styrene and thermoplastic polyurethane is manufactured using a [...] Read more.
To reveal the potential and limits of multi-material three-dimensional (3D) printed parts in droplet-based additive manufacturing, a study combining tensile experiments and 3D imaging technique is proposed. A polymeric composite structure made of acrylonitrile butadiene styrene and thermoplastic polyurethane is manufactured using a two extrusion head printer. The quality of the interface between the two thermoplastics is quantified by adjusting the number of intertwining droplets at the interface. Tensile experiments assisted with digital image correlation are performed with two-interface orientation to discriminate shearing and traction at the interface. The 3D imaging results, which are based on X-ray micro-tomography, show the distinct features of droplet-based additive manufacturing in terms of porosity content and connectivity. Interface properties are found to control, in an incomparable way, the mechanical response. It is found that the interface quality is determinant for enhancing the ultimate performance whereas the interface orientation is found to be the perfect leverage for varying the slope of the linear part. Full article
(This article belongs to the Special Issue Three-Dimensional Structures: Fabrication and Application)
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Open AccessArticle
Surface Modification of Poly(lactic acid) Fabrics with Plasma Pretreatment and Chitosan/Siloxane Polyesters Coating for Color Strength Improvement
Polymers 2017, 9(8), 371; https://doi.org/10.3390/polym9080371
Received: 12 July 2017 / Revised: 3 August 2017 / Accepted: 16 August 2017 / Published: 18 August 2017
Cited by 7 | Viewed by 1981 | PDF Full-text (1289 KB) | HTML Full-text | XML Full-text
Abstract
As people in the 21st century become increasingly environmentally aware, environmentally friendly products have come into focus. As such, environmentally friendly textiles and eco-textiles have become an international trend in research and development. Poly(lactic acid) fiber, which is biodegradable, holds much promise, but [...] Read more.
As people in the 21st century become increasingly environmentally aware, environmentally friendly products have come into focus. As such, environmentally friendly textiles and eco-textiles have become an international trend in research and development. Poly(lactic acid) fiber, which is biodegradable, holds much promise, but it is difficult to deep dye. This study used chitosan, succine anhydride, siloxane, and polyethylene glycol to produce a series of chitosan/siloxane polyesters that have a hydrophilic component (chitosan) and a hydrophobic component (siloxane), and this chitosan/siloxane polyester can be coated on poly(lactic acid) fiber, which we had subjected to Argon plasma treatment to increase their antimicrobial properties and to increase the fibers dyeing efficiency. The study shows that, after the surface plasma treatment, longer PEG chain lengths resulted in higher K/S values. This result suggests that the surface plasma pretreatment and chitosan/siloxane polyesters coating showed that lower ∆E values result in more leveling dyeing of poly(lactic acid) fiber. Full article
(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)
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Open AccessArticle
Molecular Dynamics Study on the Effect of Surface Hydroxyl Groups on Three-Phase Wettability in Oil-Water-Graphite Systems
Polymers 2017, 9(8), 370; https://doi.org/10.3390/polym9080370
Received: 30 June 2017 / Revised: 15 August 2017 / Accepted: 15 August 2017 / Published: 18 August 2017
Cited by 6 | Viewed by 2403 | PDF Full-text (4661 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a hydroxylated graphite surface is generated as a hydrophilic oleophobic material for the application of oil-water separation, and the effects of hydroxyl density on the three-phase wettability are studied in oil-water-graphite systems. We analyze the adsorption of water molecules on [...] Read more.
In this paper, a hydroxylated graphite surface is generated as a hydrophilic oleophobic material for the application of oil-water separation, and the effects of hydroxyl density on the three-phase wettability are studied in oil-water-graphite systems. We analyze the adsorption of water molecules on the hydroxylated surfaces and obtain the relationship between water-oil-solid interfacial properties and the hydroxyl density, which results from the synthetic effects of the orientation of molecules and hydrogen bonds. With the increase of hydroxyl density, the water-solid contact angle first decreases rapidly, and then remains constant. The density of the hydrogen bond formed between hydroxyls and water molecules in the adsorption layer can explain the regularity of the three-phase wettability. The orientation of the water molecules in the adsorption layer shows insignificant variation, owing to the hydrogen bond network formed between the water molecules; thus, little change is observed in the hydrogen bond density in the adsorption layer. Full article
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Open AccessArticle
Constraining Polymers into β-Turns: Miscibility and Phase Segregation Effects in Lipid Monolayers
Polymers 2017, 9(8), 369; https://doi.org/10.3390/polym9080369
Received: 28 July 2017 / Revised: 11 August 2017 / Accepted: 13 August 2017 / Published: 17 August 2017
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Abstract
Abstract: Investigation of model biomembranes and their interactions with natural or synthetic macromolecules are of great interest to design membrane systems with specific properties such as drug-delivery. Here we study the behavior of amphiphilic β-turn mimetic polymer conjugates at the air–water interface [...] Read more.
Abstract: Investigation of model biomembranes and their interactions with natural or synthetic macromolecules are of great interest to design membrane systems with specific properties such as drug-delivery. Here we study the behavior of amphiphilic β-turn mimetic polymer conjugates at the air–water interface and their interactions with lipid model membranes. For this endeavor we synthesized two different types of conjugates containing either hydrophobic polyisobutylene (PIB, Mn = 5000 g·mol−1) or helical poly(n-hexyl isocyanate) (PHIC, Mn = 4000 g·mol−1), both polymers being immiscible, whereas polyisobutylene as a hydrophobic polymer can incorporate into lipid membranes. The conjugates were investigated using Langmuir-film techniques coupled with epifluorescence microscopy and AFM (Atomic Force Microscopy), in addition to their phase behavior in mixed lipid/polymer membranes composed of DPPC (dipalmitoyl-sn-glycero-3-phosphocholine). It was found that the DPPC monolayers are strongly disturbed by the presence of the polymer conjugates and that domain formation of the polymer conjugates occurs at high surface pressures (π > 30 mN·m−1). Full article
(This article belongs to the Special Issue From Amphiphilic to Polyphilic Polymers)
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Open AccessFeature PaperArticle
The Effect of Hydrogen Bonding on Radical Semi-Batch Copolymerization of Butyl Acrylate and 2-Hydroxyethyl Acrylate
Polymers 2017, 9(8), 368; https://doi.org/10.3390/polym9080368
Received: 24 July 2017 / Revised: 12 August 2017 / Accepted: 15 August 2017 / Published: 17 August 2017
Cited by 2 | Viewed by 2134 | PDF Full-text (1422 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The radical copolymerization of butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) was investigated under batch and semi-batch operations, with a focus on the influence of hydrogen-bonding on acrylate backbiting. The effect of hydrogen bonding on HEA to BA relative incorporation rates during copolymerization, [...] Read more.
The radical copolymerization of butyl acrylate (BA) and 2-hydroxyethyl acrylate (HEA) was investigated under batch and semi-batch operations, with a focus on the influence of hydrogen-bonding on acrylate backbiting. The effect of hydrogen bonding on HEA to BA relative incorporation rates during copolymerization, previously seen in low-conversion kinetic studies, was also observed under high-conversion semi-batch conditions. However, overall reaction rates (as indicated by free monomer concentrations), polymer molar masses, and branching levels did not vary as copolymer HEA content was increased from 0 to 40 wt % in the semi-batch system. In contrast, introduction of a H-bonding solvent, n-pentanol, led to an observable decrease in branching levels, and branching levels were also reduced in batch (co)polymerizations with HEA. These differences can be attributed to the low levels of unreacted HEA in the starved-feed semi-batch system. Full article
(This article belongs to the Special Issue Tailored Polymer Synthesis by Advanced Polymerization Techniques)
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Open AccessArticle
pH-Induced Association and Dissociation of Intermolecular Complexes Formed by Hydrogen Bonding between Diblock Copolymers
Polymers 2017, 9(8), 367; https://doi.org/10.3390/polym9080367
Received: 26 July 2017 / Revised: 12 August 2017 / Accepted: 15 August 2017 / Published: 17 August 2017
Cited by 3 | Viewed by 1710 | PDF Full-text (3638 KB) | HTML Full-text | XML Full-text
Abstract
Poly(sodium styrenesulfonate)–block–poly(acrylic acid) (PNaSS–b–PAA) and poly(sodium styrenesulfonate)–blockpoly(N-isopropylacrylamide) (PNaSS–bPNIPAM) were prepared via reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a PNaSS-based macro-chain transfer agent. The molecular weight distributions (Mw/M [...] Read more.
Poly(sodium styrenesulfonate)–block–poly(acrylic acid) (PNaSS–b–PAA) and poly(sodium styrenesulfonate)–blockpoly(N-isopropylacrylamide) (PNaSS–bPNIPAM) were prepared via reversible addition–fragmentation chain transfer (RAFT) radical polymerization using a PNaSS-based macro-chain transfer agent. The molecular weight distributions (Mw/Mn) of PNaSS–b–PAA and PNaSS–bPNIPAM were 1.18 and 1.39, respectively, suggesting that these polymers have controlled structures. When aqueous solutions of PNaSS–b–PAA and PNaSS–bPNIPAM were mixed under acidic conditions, water-soluble PNaSS–bPAA/PNaSS–bPNIPAM complexes were formed as a result of hydrogen bonding interactions between the pendant carboxylic acids in the PAA block and the pendant amide groups in the PNIPAM block. The complex was characterized by 1H NMR, dynamic light scattering, static light scattering, and transmission electron microscope measurements. The light scattering intensity of the complex depended on the mixing ratio of PNaSS–b–PAA and PNaSS–bPNIPAM. When the molar ratio of the N-isopropylacrylamide (NIPAM) and acrylic acid (AA) units was near unity, the light scattering intensity reached a maximum, indicating stoichiometric complex formation. The complex dissociated at a pH higher than 4.0 because the hydrogen bonding interactions disappeared due to deprotonation of the pendant carboxylic acids in the PAA block. Full article
(This article belongs to the Special Issue Polymer Micelles) Printed Edition available
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Open AccessArticle
Pulp Fines—Characterization, Sheet Formation, and Comparison to Microfibrillated Cellulose
Polymers 2017, 9(8), 366; https://doi.org/10.3390/polym9080366
Received: 28 July 2017 / Revised: 13 August 2017 / Accepted: 13 August 2017 / Published: 17 August 2017
Cited by 4 | Viewed by 2062 | PDF Full-text (4455 KB) | HTML Full-text | XML Full-text
Abstract
In the pulp and paper industry different types of pulp or fiber fines are generated during the pulping (primary fines, mechanical fines), and/or the refining process (secondary fines). Besides fibers, these cellulosic microparticles are a further component of the paper network. Fines, which [...] Read more.
In the pulp and paper industry different types of pulp or fiber fines are generated during the pulping (primary fines, mechanical fines), and/or the refining process (secondary fines). Besides fibers, these cellulosic microparticles are a further component of the paper network. Fines, which are defined as the fraction of pulp that is able to pass through a mesh screen or a perforated plate having a hole diameter of 76 μm, are known to influence the properties of the final paper product. To better understand the effect and properties of this material, fines have to be separated from the pulp and investigated as an independent material. In the present study, fines are isolated from the pulp fraction by means of a laboratory pressure screen. To allow for further processing, the solids content of the produced fines suspension was increased using dissolved air flotation. Morphological properties of different types of fines and other cellulosic microparticles, such as microfibrillated celluloses (MFC) are determined and compared to each other. Furthermore, handsheets are prepared from these materials and properties, such as apparent density, contact angle, modulus of elasticity, and strain are measured giving similar results for the analyzed types of fines in comparison to the tested MFC grades. The analysis of the properties of fiber fines contributes on the one hand to a better understanding of how these materials influences the final paper products, and on the other hand, helps in identifying other potential applications of this material. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessArticle
Biodegradation Studies of Novel Fluorinated Di-Vinyl Urethane Monomers and Interaction of Biological Elements with Their Polymerized Films
Polymers 2017, 9(8), 365; https://doi.org/10.3390/polym9080365
Received: 21 June 2017 / Revised: 1 August 2017 / Accepted: 11 August 2017 / Published: 17 August 2017
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Abstract
The monomeric components of resin composites in dental restorative materials are susceptible to hydrolysis in the oral cavity. The main objective of this study was to assess the bio-stability of fluorinated urethane dimethacrylates and determine the nature of fluoro-chemistry interactions with protein and [...] Read more.
The monomeric components of resin composites in dental restorative materials are susceptible to hydrolysis in the oral cavity. The main objective of this study was to assess the bio-stability of fluorinated urethane dimethacrylates and determine the nature of fluoro-chemistry interactions with protein and bacterial adhesion (both sources of hydrolytic activity) onto cured resin. Degradation studies were performed in the presence of either albumin (in a mildly alkaline pH) or cholesterol esterase (CE). The surface chemistry of the polymers was assessed by water contact angle measurements, pre- and post- incubation with albumin. Adhesion of Streptococcus mutans to cured resin was investigated. The fluorinated monomers were more stable against degradation when compared to the commercial monomer bisphenol A-diglycidyl methacrylate (BisGMA). While fluorinated monomers showed hydrolytic stability with respect to CE, all fluorinated monomers underwent some degree of degradation with albumin. The fluoro-chemistry did not reduce protein and/or bacterial adhesion onto the surface, however post incubation with albumin, the fluorinated surfaces still presented hydrophobic character as determined by the high contact angle values ranging from 79° to 86°. These monomers could potentially be used to increase the hydrophobicity of polymeric composites and provide a means to moderate esterolytic degradation associated with the monomeric component of the polymers within the oral cavity. Full article
(This article belongs to the Special Issue Advance of Polymers Applied to Biomedical Applications: Biointerface)
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Open AccessFeature PaperReview
Hydrogel Based Sensors for Biomedical Applications: An Updated Review
Polymers 2017, 9(8), 364; https://doi.org/10.3390/polym9080364
Received: 20 July 2017 / Revised: 10 August 2017 / Accepted: 12 August 2017 / Published: 16 August 2017
Cited by 35 | Viewed by 3694 | PDF Full-text (1135 KB) | HTML Full-text | XML Full-text
Abstract
Biosensors that detect and convert biological reactions to a measurable signal have gained much attention in recent years. Between 1950 and 2017, more than 150,000 papers have been published addressing the applications of biosensors in different industries, but to the best of our [...] Read more.
Biosensors that detect and convert biological reactions to a measurable signal have gained much attention in recent years. Between 1950 and 2017, more than 150,000 papers have been published addressing the applications of biosensors in different industries, but to the best of our knowledge and through careful screening, critical reviews that describe hydrogel based biosensors for biomedical applications are rare. This review discusses the biomedical application of hydrogel based biosensors, based on a search performed through Web of Science Core, PubMed (NLM), and Science Direct online databases for the years 2000–2017. In this review, we consider bioreceptors to be immobilized on hydrogel based biosensors, their advantages and disadvantages, and immobilization techniques. We identify the hydrogels that are most favored for this type of biosensor, as well as the predominant transduction strategies. We explain biomedical applications of hydrogel based biosensors including cell metabolite and pathogen detection, tissue engineering, wound healing, and cancer monitoring, and strategies for small biomolecules such as glucose, lactate, urea, and cholesterol detection are identified. Full article
(This article belongs to the Special Issue Hydrogels in Tissue Engineering and Regenerative Medicine)
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Open AccessArticle
Hydrogen-Bonded Polymer Complex Thin Film of Poly(2-oxazoline) and Poly(acrylic acid)
Polymers 2017, 9(8), 363; https://doi.org/10.3390/polym9080363
Received: 7 July 2017 / Revised: 9 August 2017 / Accepted: 11 August 2017 / Published: 15 August 2017
Cited by 8 | Viewed by 2119 | PDF Full-text (1963 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The hydrogen-bonded polymer complex thin film of poly(2-ethyl-2-oxazoline) (PEOX) and poly(acrylic acid) (PAA) was fabricated with layer-by-layer (LbL) assembly. The film shows exponential growth at early stage and transfers to linear growth after 10 assembling cycles, and the stable thickness increment per assembling [...] Read more.
The hydrogen-bonded polymer complex thin film of poly(2-ethyl-2-oxazoline) (PEOX) and poly(acrylic acid) (PAA) was fabricated with layer-by-layer (LbL) assembly. The film shows exponential growth at early stage and transfers to linear growth after 10 assembling cycles, and the stable thickness increment per assembling cycle in the linear region could be higher than 100 nm. The film growth should be related with polymer chain diffusion during LbL assembly. The effects of assembling time, rinsing time, temperature, pH value, concentration and molecular weight on the thin film growth were investigated. Increasing the assembly time, the temperature and the concentration is favorable to produce the thick film. Prolonging rinsing time is good for preparing smooth film. The film can be constructed below pH 4.5 while the prepared film will not completely dissolve until pH value elevates to 7.0. Molecular weight has a subtle effect on the PEOX/PAA film growth. The PEOX-PAA pair that has a big molecular weight contrast shows fast film growth in the linear region. Full article
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Open AccessArticle
Aromatic Modification of Low Molecular Weight PEI for Enhanced Gene Delivery
Polymers 2017, 9(8), 362; https://doi.org/10.3390/polym9080362
Received: 17 July 2017 / Revised: 3 August 2017 / Accepted: 3 August 2017 / Published: 15 August 2017
Cited by 3 | Viewed by 1914 | PDF Full-text (6491 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Low molecular weight polyethylenimine (1800 Da, also referred to as oligoethylenimines, OEI) was modified with amino acids, including two aromatic amino acids (tryptophan, phenylalanine) and an aliphatic amino acid (leucine). The substitution degree of amino acids could be controlled by adjusting the feeding [...] Read more.
Low molecular weight polyethylenimine (1800 Da, also referred to as oligoethylenimines, OEI) was modified with amino acids, including two aromatic amino acids (tryptophan, phenylalanine) and an aliphatic amino acid (leucine). The substitution degree of amino acids could be controlled by adjusting the feeding mole ratio of the reactants. Fluorescence spectroscopy and circular dichroism experiments demonstrated that the indole ring of tryptophan may intercalate into the DNA base pairs and contribute to efficient DNA condensation. In vitro gene expression results revealed that the modified OEIs (OEI-AAs) may provide higher transfection efficiency even than high molecular weight polyethylenimine (25 kDa, PEI), especially the aromatic tryptophan substituted OEI. Moreover, OEI-AAs exhibited excellent serum tolerance, and up to 137 times higher transfection efficiency than PEI 25 kDa that was obtained in the presence of serum. The cytotoxicity of OEI-AAs is much lower than PEI 25 kDa. This study may afford a new method for the development of low molecular weight oligomeric non-viral gene vectors with both high efficiency and biocompatibility. Full article
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Open AccessArticle
Synthesis and Application of Novel Magnetic Ion-Imprinted Polymers for Selective Solid Phase Extraction of Cadmium (II)
Polymers 2017, 9(8), 360; https://doi.org/10.3390/polym9080360
Received: 4 July 2017 / Revised: 10 August 2017 / Accepted: 10 August 2017 / Published: 14 August 2017
Cited by 4 | Viewed by 2281 | PDF Full-text (3856 KB) | HTML Full-text | XML Full-text
Abstract
Ion-imprinted polymers (IIPs) have received much attention in the fields of separation and purification. Nevertheless, selectivity of IIPs for trace target ions in complicated matrix remains a challenge. In this work, a cadmium magnetic ion-imprinted polymer (MIIP) was synthesized via surface imprinting, using [...] Read more.
Ion-imprinted polymers (IIPs) have received much attention in the fields of separation and purification. Nevertheless, selectivity of IIPs for trace target ions in complicated matrix remains a challenge. In this work, a cadmium magnetic ion-imprinted polymer (MIIP) was synthesized via surface imprinting, using methacrylic acid and acrylamide as dual functional monomers, vinyltrimethoxysilane as ligand, Fe3O4@SiO2 as support, azodiisobutyronitrile as initiator, and ethylene glycol dimethacrylate as crosslinker. The MIIP was characterized by transmission electron microscopy, infrared spectroscopy, thermal gravimetric analysis, and a vibrating sample magnetometer. The maximum adsorption capacities of the MIIP and magnetic non-imprinted polymer for Cd(II) were 46.8 and 14.7 mg·g−1, respectively. The selectivity factors of Pb(II), Cu(II), and Ni(II) were 3.17, 2.97, and 2.57, respectively, which were greater than 1. The adsorption behavior of Cd(II) followed the Freundlich isotherm and a pseudo second order model. The MIIP was successfully used for the selective extraction and determination of trace Cd(II) in representative rice samples. The limit of detection and recovery of the method was 0.05 µg·L−1 and 80–103%, respectively, with a relative standard deviation less than 4.8%. This study shows that MIIP provides an attractive strategy for heavy metal detection. Full article
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Open AccessArticle
Surface Molecularly Imprinted Polymer Film with Poly(p-aminothiophenol) Outer Layer Coated on Gold Nanoparticles Inner Layer for Highly Sensitive and Selective Sensing Paraoxon
Polymers 2017, 9(8), 359; https://doi.org/10.3390/polym9080359
Received: 19 July 2017 / Revised: 9 August 2017 / Accepted: 10 August 2017 / Published: 12 August 2017
Cited by 5 | Viewed by 2196 | PDF Full-text (2311 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This paper presents the fabrication of a molecularly imprinted, polymer-based disposable electrochemical sensor for paraoxon (PO) determination. The sensor was based on a screen-printed carbon electrode (SPCE) modified with a surface molecularly imprinted poly (p-aminothiophenol) (PATP)/gold nanoparticles (AuNPs) composite film, which [...] Read more.
This paper presents the fabrication of a molecularly imprinted, polymer-based disposable electrochemical sensor for paraoxon (PO) determination. The sensor was based on a screen-printed carbon electrode (SPCE) modified with a surface molecularly imprinted poly (p-aminothiophenol) (PATP)/gold nanoparticles (AuNPs) composite film, which consisted of a PATP outer layer and an AuNPs inner layer. We report a novel strategy, combining surface molecularly imprinting and self-assembly directed electro-polymerization with high densely imprinting PO molecules in the PATP/AuNPs film. Firstly, AuNPs were in situ electrodeposited at the electrode surface, and then assembled with electropolmerizable functional monomer p-aminothiophenol (ATP). Subsequently, PO molecules were assembled onto the ATP monolayer-modified AuNPs, forming a basis of surface molecular imprinting. After that, replenished PO molecules were embedded in the PATP/AuNPs film by PO and the ATP molecular self-assembly directed electro-polymerization in the polymerization precursor mixture. The resulting imprinted PATP/AuNPs/SPCE possesses high sensitivity, affinity, and selectivity toward PO, with a low detection limit of 1 × 10−9 M. The proposed sensor was successfully applied for the determination of PO in fruit and vegetables, giving satisfactory recoveries. The strategy reported herein can be further expected to fabricate various molecular imprinted sensors for the determination of other pesticide residuals. Full article
(This article belongs to the Special Issue Polymer Based Bio-Sensors)
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Open AccessArticle
Influence of Temperature on the Electromechanical Properties of Ionic Liquid-Doped Ionic Polymer-Metal Composite Actuators
Polymers 2017, 9(8), 358; https://doi.org/10.3390/polym9080358
Received: 28 July 2017 / Revised: 8 August 2017 / Accepted: 9 August 2017 / Published: 12 August 2017
Cited by 7 | Viewed by 2740 | PDF Full-text (6327 KB) | HTML Full-text | XML Full-text
Abstract
Ionic polymer-metal composite (IPMC) actuators have considerable potential for a wide range of applications. Although IPMC actuators are widely studied for their electromechanical properties, most studies have been conducted at the ambient conditions. The electromechanical performance of IPMC actuators at higher temperature is [...] Read more.
Ionic polymer-metal composite (IPMC) actuators have considerable potential for a wide range of applications. Although IPMC actuators are widely studied for their electromechanical properties, most studies have been conducted at the ambient conditions. The electromechanical performance of IPMC actuators at higher temperature is still far from understood. In this study, the effect of temperature on the electromechanical behavior (the rate of deformation and curvature) and electrochemical behavior (current flow) of ionic liquid doped IPMC actuators are examined and reported. Both electromechanical and electrochemical studies were conducted in air at temperatures ranging from 25 °C to 90 °C. Electromechanically, the actuators showed lower cationic curvature with increasing temperature up to 70 °C and a slower rate of deformation with increasing temperature up to 50 °C. A faster rate of deformation was recorded at temperatures higher than 50 °C, with a maximum rate at 60 °C. The anionic response showed a lower rate of deformation and a higher anionic curvature with increasing temperatures up to 50 °C with an abrupt increase in the rate of deformation and decrease of curvature at 60 °C. In both cationic and anionic responses, actuators started to lose functionality and show unpredictable performance for temperatures greater than 60 °C, with considerable fluctuations at 70 °C. Electrochemically, the current flow across the actuators was increased gradually with increasing temperature up to 80 °C during the charging and discharging cycles. A sudden increase in current flow was recorded at 90 °C indicating a shorted circuit and actuator failure. Full article
(This article belongs to the Special Issue Electroactive Polymers and Gels)
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Open AccessArticle
Development of Synergistic Antimicrobial Coating of p-Aramid Fibers Using Ag Nanoparticles and Glycidyltrimethylammonium Chloride (GTAC) without the Aid of a Cross-Linking Agent
Polymers 2017, 9(8), 357; https://doi.org/10.3390/polym9080357
Received: 5 July 2017 / Revised: 3 August 2017 / Accepted: 6 August 2017 / Published: 11 August 2017
Cited by 1 | Viewed by 1706 | PDF Full-text (2981 KB) | HTML Full-text | XML Full-text
Abstract
Functional p-aramid fibers that can express antimicrobial activity were produced by simple processing of silver nanoparticles (AgNPs), which are well known as antimicrobial agents, by using glycidyltrimethylammonium chloride (GTAC), a quaternary ammonium salt. P-aramid fibers were treated with GTAC by the pad-dry-cure process [...] Read more.
Functional p-aramid fibers that can express antimicrobial activity were produced by simple processing of silver nanoparticles (AgNPs), which are well known as antimicrobial agents, by using glycidyltrimethylammonium chloride (GTAC), a quaternary ammonium salt. P-aramid fibers were treated with GTAC by the pad-dry-cure process and put into an Ag colloid solution for reactions at 40 °C for 90 min to prepare GTAC/AgNPs-treated p-aramid fibers. Through these processes, GTAC was used as a substitute for existing cross-linking agents. The changes in the degree of attachment of AgNPs to the surface of p-aramid fibers were determined using a scanning electron microscope according to parameters such as GTAC concentration, Ag colloid concentration, and reaction temperature. Through this study, the following results were obtained: (i) The tensile strength of AgNPs/GTAC-treated p-aramid fibers was found to be about 80% of that of untreated p-aramid fibers; (ii) Thermogravimetric analysis showed that the thermal stability of p-aramid fibers did not change much after GTAC/AgNPs treatment and (iii) Antimicrobial activity analysis showed that AgNPs/GTAC-treated p-aramid fibers exhibited superior antibacterial properties compared to untreated p-aramid fibers, which may or may not be the effect of GTAC or AgNPs, or both. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessArticle
Directional Alignment of Polyfluorene Copolymers at Patterned Solid-Liquid Interfaces
Polymers 2017, 9(8), 356; https://doi.org/10.3390/polym9080356
Received: 26 June 2017 / Revised: 2 August 2017 / Accepted: 3 August 2017 / Published: 11 August 2017
Cited by 1 | Viewed by 1729 | PDF Full-text (3607 KB) | HTML Full-text | XML Full-text
Abstract
Polyfluorene and its derivatives have been recognized as efficient light-emitting semiconductors. However, directional alignment of polyfluorene copolymers at a large scale has rarely been observed, in particular for the two relatively more amorphous members of poly-9,9-dioctylfluorene-co-bethiadisazole (F8BT) and poly-(9,9-dioctylfluorenyl-2,7-diyl)-co-(N, [...] Read more.
Polyfluorene and its derivatives have been recognized as efficient light-emitting semiconductors. However, directional alignment of polyfluorene copolymers at a large scale has rarely been observed, in particular for the two relatively more amorphous members of poly-9,9-dioctylfluorene-co-bethiadisazole (F8BT) and poly-(9,9-dioctylfluorenyl-2,7-diyl)-co-(N,N0-diphenyl)-N,N′di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) molecules. Furthermore, the directional alignment of PFB has not been observed so far due to the triphenylamine units in its molecular structures. We present, in this work, a solution-processible method to achieve large-scale alignment of F8BT and PFB molecules into fibers as long as millimeters in a defined direction. Spin-coating the polymer film on to a glass substrate patterned by one-dimensional dielectric nano-grating structures through interference lithography and subsequent modification using 1,5-pentanediol have been used in all of the preparation procedures. Polymer fibers have been obtained in an arrangement parallel to the grating lines. The microscopic, spectroscopic, and photoconductive performances verified the formation and the quality of these directionally-aligned polymeric fibers. Full article
(This article belongs to the Special Issue Host-Guest Polymer Complexes) Printed Edition available
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Open AccessArticle
Isolation and Characterization of Cellulose Nanocrystals from Oil Palm Mesocarp Fiber
Polymers 2017, 9(8), 355; https://doi.org/10.3390/polym9080355
Received: 12 July 2017 / Revised: 9 August 2017 / Accepted: 9 August 2017 / Published: 11 August 2017
Cited by 7 | Viewed by 2099 | PDF Full-text (4689 KB) | HTML Full-text | XML Full-text
Abstract
The aim was to explore the utilization of oil palm mesocarp fiber (OPMF) as a source for the production of cellulose nanocrystals (CNC). OPMF was first treated with alkali and then bleached before the production of CNC by acid hydrolysis (H2SO [...] Read more.
The aim was to explore the utilization of oil palm mesocarp fiber (OPMF) as a source for the production of cellulose nanocrystals (CNC). OPMF was first treated with alkali and then bleached before the production of CNC by acid hydrolysis (H2SO4). The produced materials were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), a scanning electron microscope (SEM) and a transmission electron microscope (TEM). It was proven that acid hydrolysis can increase the crystallinity of bleached OPMF and reduce the dimension of cellulose to nano scale. Changes in the peaks of the FTIR spectrum at 2852 (C-H stretching), 1732 (C=O stretching) and 1234 cm−1 (C-O stretching) indicated that the alkali treatment completely removed hemicelluloses and lignin from the fiber surface. This can be seen from the thermogram obtained from the TGA characterization. Morphological characterization clearly showed the formation of rod-shaped CNCs. The promising results prove that OPMF is a valuable source for the production of CNC. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Open AccessFeature PaperReview
Poly(3,4-ethylenedioxythiophene) (PEDOT) Derivatives: Innovative Conductive Polymers for Bioelectronics
Polymers 2017, 9(8), 354; https://doi.org/10.3390/polym9080354
Received: 26 June 2017 / Revised: 7 August 2017 / Accepted: 8 August 2017 / Published: 11 August 2017
Cited by 24 | Viewed by 5564 | PDF Full-text (3017 KB) | HTML Full-text | XML Full-text
Abstract
Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (conductivity, stability, transparency and biocompatibility). The gold standard material is the commercially available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect [...] Read more.
Poly(3,4-ethylenedioxythiophene)s are the conducting polymers (CP) with the biggest prospects in the field of bioelectronics due to their combination of characteristics (conductivity, stability, transparency and biocompatibility). The gold standard material is the commercially available poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). However, in order to well connect the two fields of biology and electronics, PEDOT:PSS presents some limitations associated with its low (bio)functionality. In this review, we provide an insight into the synthesis and applications of innovative poly(ethylenedioxythiophene)-type materials for bioelectronics. First, we present a detailed analysis of the different synthetic routes to (bio)functional dioxythiophene monomer/polymer derivatives. Second, we focus on the preparation of PEDOT dispersions using different biopolymers and biomolecules as dopants and stabilizers. To finish, we review the applications of innovative PEDOT-type materials such as biocompatible conducting polymer layers, conducting hydrogels, biosensors, selective detachment of cells, scaffolds for tissue engineering, electrodes for electrophysiology, implantable electrodes, stimulation of neuronal cells or pan-bio electronics. Full article
(This article belongs to the Special Issue Conductive Polymers 2017)
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Open AccessArticle
Facile, Efficient Copolymerization of Ethylene with Norbornene-Containing Dienes Promoted by Single Site Non-Metallocene Oxovanadium(V) Catalytic System
Polymers 2017, 9(8), 353; https://doi.org/10.3390/polym9080353
Received: 23 July 2017 / Revised: 8 August 2017 / Accepted: 8 August 2017 / Published: 11 August 2017
Cited by 2 | Viewed by 1674 | PDF Full-text (2200 KB) | HTML Full-text | XML Full-text
Abstract
Non-metallocene oxovanadium(V) complexes bearing either [ONNO]-type amine pyridine bis(phenolate) ligands or [ONN]-type amine pyridine phenolate ligands were employed as efficient catalysts to copolymerize ethylene with several unsymmetrical norbornene-containing dienes, such as 5-vinyl-2-norbornene (VNB), 5-ethylidene-2-norbornene (ENB) or dicyclopentadiene (DCPD), producing copolymers with high comonomer [...] Read more.
Non-metallocene oxovanadium(V) complexes bearing either [ONNO]-type amine pyridine bis(phenolate) ligands or [ONN]-type amine pyridine phenolate ligands were employed as efficient catalysts to copolymerize ethylene with several unsymmetrical norbornene-containing dienes, such as 5-vinyl-2-norbornene (VNB), 5-ethylidene-2-norbornene (ENB) or dicyclopentadiene (DCPD), producing copolymers with high comonomer incorporations (VNB: 33.0 mol %; ENB: 30.4 mol %; DCPD: 31.6 mol %, respectively) and high molecular weight (VNB: 86.4 kDa; ENB: 256 kDa; DCPD: 86.4 kDa, respectively). The enchainment of the dienes was proven to be exclusive of vinyl-addition via the C=C double bond of the norbornene ring while the other double bond was retained near the backbone without crosslinking. During the copolymerization of ethylene with ENB, a positive ‘comonomer effect’ was observed. The catalytic activities of the catalysts as well as the molecular weights and comonomer incorporations of the resultant copolymers could be tuned within a wide range by varying the structures of the catalysts and copolymerization conditions. The [ONN]-type oxovanadium(V) complexes showed higher catalytic activities than those of [ONNO]-type oxovanadium(V) complexes, irrespective of the structure of the dienes. In addition, the dominant chain transfer pathway of the non-metallocene oxovanadium(V) catalytic system promoted copolymerization was proven to be transfer to aluminum compounds. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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