Polymers

16 pages, 1321 KiB

Open AccessArticle

The Effect of Co-Monomer Content on the Swelling/Shrinking and Mechanical Behaviour of Individually Adsorbed PNIPAM Microgel Particles

by Anna Burmistrova, Marcel Richter, Michael Eisele, Cagri Üzüm and Regine Von Klitzing^*

Stranski-Laboratorium für Physikalische und Theoretische Chemie, Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, D-10623 Berlin, Germany

Polymers 2011, 3(4), 1575-1590; https://doi.org/10.3390/polym3041575 - 26 Sep 2011

Cited by 126 | Viewed by 14764

Abstract

The swelling/deswelling behaviour of microgel particles in the bulk and at the surface was studied and correlated to their mechanical properties. We focused on two kinds of particles: pure PNIPAM and PNIPAM-co-AAc particles. It was shown that the two step volume [...] Read more.

The swelling/deswelling behaviour of microgel particles in the bulk and at the surface was studied and correlated to their mechanical properties. We focused on two kinds of particles: pure PNIPAM and PNIPAM-co-AAc particles. It was shown that the two step volume phase transition found for PNIPAM-co-AAc particles in the bulk disappears after the adsorption at the surface and only a one step transition was identified. The transition temperature increased strongly with increasing the co-monomer content. The dependence of the Young’s modulus of the adsorbed microgel particles on the temperature and the co-monomer content was discussed. The investigations were performed via DLS and SFM. Full article

(This article belongs to the Special Issue Polymer Nanogels and Microgels)

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9 pages, 535 KiB

Open AccessReview

Guiding Light in Electro-Optic Polymers

by Anna L. Pyayt

E.L. Ginzton Laboratory, Stanford University, Nano Building, 348 Via Pueblo Mall, Stanford, CA 94305, USA

Polymers 2011, 3(4), 1591-1599; https://doi.org/10.3390/polym3041591 - 26 Sep 2011

Cited by 10 | Viewed by 8228

Abstract

Electro-optic polymers have unique photonic, electro-optic and mechanical properties that make them attractive to use in a wide range of devices starting from ultra-high bandwidth light modulators for optical communications to miniature low power components for on-chip optical interconnects. The main building blocks [...] Read more.

Electro-optic polymers have unique photonic, electro-optic and mechanical properties that make them attractive to use in a wide range of devices starting from ultra-high bandwidth light modulators for optical communications to miniature low power components for on-chip optical interconnects. The main building blocks of those devices are optical waveguides, that due to versatility of the polymers can be fabricated as either traditional multi-layer polymer structures, silicon nano-slots filled with the polymer, or dynamically created waveguides based on field-induced guiding. In this paper we cover various types of waveguides and analyze their optimum designs depending on application. Full article

(This article belongs to the Special Issue Polymers for Optical Applications)

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7 pages, 230 KiB

Open AccessArticle

Preparation and Characterization of Organic-Inorganic Hybrid Hydrogel Electrolyte Using Alkaline Solution

by Masanobu Chiku, Shoji Tomita, Eiji Higuchi and Hiroshi Inoue^*

Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan

Polymers 2011, 3(4), 1600-1606; https://doi.org/10.3390/polym3041600 - 26 Sep 2011

Cited by 6 | Viewed by 7891

Abstract

Organic-inorganic hybrid hydrogel electrolytes were prepared by mixing hydrotalcite, cross-linked potassium poly(acrylate) and 6 M KOH solution. The organic-inorganic hybrid hydrogel electrolytes had high ionic conductivity (0.456–0.540 S cm⁻¹) at 30 °C. Moreover, the mechanical strength of the hydrogel electrolytes was [...] Read more.

Organic-inorganic hybrid hydrogel electrolytes were prepared by mixing hydrotalcite, cross-linked potassium poly(acrylate) and 6 M KOH solution. The organic-inorganic hybrid hydrogel electrolytes had high ionic conductivity (0.456–0.540 S cm⁻¹) at 30 °C. Moreover, the mechanical strength of the hydrogel electrolytes was high enough to form a 2–3 mm thick freestanding membrane because of the reinforcement with hydrotalcite. Full article

(This article belongs to the Special Issue Polymer Nanogels and Microgels)

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45 pages, 2117 KiB

Open AccessReview

Polysaccharides: The “Click” Chemistry Impact

by Pierre-Henri Elchinger^1,2, Pierre-Antoine Faugeras^1,2, Benjamin Boëns¹, François Brouillette², Daniel Montplaisir², Rachida Zerrouki¹

and Romain Lucas^3,*

¹ Laboratoire de Chimie des Substances Naturelles, EA1069, 123 Avenue Albert Thomas, 87060 Limoges, France

² Centre de recherche sur les matériaux lignocellulosiques, Université du Québec à Trois-Rivières, 3351 boul. des Forges, C.P. 500, Trois-Rivières (QC) G9A 5H7, France

³ Laboratoire Science des Procédés Céramiques et de Traitements de Surface - UMR CNRS 6638 12 Rue Atlantis, F-87068, Limoges, France

Polymers 2011, 3(4), 1607-1651; https://doi.org/10.3390/polym3041607 - 27 Sep 2011

Cited by 83 | Viewed by 18136

Abstract

Polysaccharides are complex but essential compounds utilized in many areas such as biomaterials, drug delivery, cosmetics, food chemistry or renewable energy. Modifications and functionalizations of such polymers are often necessary to achieve molecular structures of interest. In this area, the emergence of the [...] Read more.

Polysaccharides are complex but essential compounds utilized in many areas such as biomaterials, drug delivery, cosmetics, food chemistry or renewable energy. Modifications and functionalizations of such polymers are often necessary to achieve molecular structures of interest. In this area, the emergence of the “click” chemistry concept, and particularly the copper-catalyzed version of the Huisgen 1,3-dipolar cycloaddition reaction between terminal acetylenes and azides, had an impact on the polysaccharides chemistry. The present review summarizes the contribution of “click” chemistry in the world of polysaccharides. Full article

(This article belongs to the Collection Polysaccharides)

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10 pages, 499 KiB

Open AccessArticle

Novel Countercation in MMX-Type Mixed-Valence Chain Compound: Coexistence of Neutral and Protonated Amino Substituents

by Hiroaki Iguchi^1,*, Deli Jiang², Jimin Xie², Shinya Takaishi¹ and Masahiro Yamashita^1,*

¹ Department of Chemistry, Graduate School of Science, Tohoku University, 6-3 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-8578, Japan

² School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, China

Polymers 2011, 3(4), 1652-1661; https://doi.org/10.3390/polym3041652 - 6 Oct 2011

Cited by 6 | Viewed by 7006

Abstract

The first MMX-type quasi-one-dimensional (Q1D) Pt chain complex (MMX chain) that contains a mono-protonated diamine as countercation, {o-(H₃NC₆H₄NH₂)}₄[Pt₂(pop)₄I]·H₂O (pop = P₂H₂O [...] Read more.

The first MMX-type quasi-one-dimensional (Q1D) Pt chain complex (MMX chain) that contains a mono-protonated diamine as countercation, {o-(H₃NC₆H₄NH₂)}₄[Pt₂(pop)₄I]·H₂O (pop = P₂H₂O₅^2–), was synthesized. According to the crystal structural analysis, –NH₂ group was hydrogen-bonded to either lattice H₂O molecule or –NH₃⁺ group in addition to typical hydrogen bond between –NH₃⁺ group and pop ligand. To control the partial deprotonation of the countercation will be an important method for achieving the high-conductive MMX-chain polymer by the hole doping. Full article

(This article belongs to the Special Issue Coordination Polymers)

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Graphical abstract

11 pages, 467 KiB

Open AccessArticle

Crystal Engineering: Synthesis and Structural Analysis of Coordination Polymers with Wavelike Properties

by Omar W. Steward^*, Miles V. Kaltenbach, Ashley B. Biernesser, Matthew J. Taylor, Katie J. Hovan, Jordan J. S. VerPlank, Ameera Haamid, Irina Karpov and Matasebia T. Munie

Department of Chemistry and Biochemistry, Bayer School of Natural and Environmental Sciences, 600 Forbes Avenue, Duquesne University, Pittsburgh, PA 15282, USA

Polymers 2011, 3(4), 1662-1672; https://doi.org/10.3390/polym3041662 - 7 Oct 2011

Cited by 6 | Viewed by 8391

Abstract

Supramolecular coordination polymers with wavelike structures have been synthesized by self-assembly and their structures analyzed using the sine trigonometric function.Slow evaporation of a methylene chloride-methanol solution of a 1:1 molar mixture of [M(tmhd)₂], where M = Co or Ni, and [...] Read more.

Supramolecular coordination polymers with wavelike structures have been synthesized by self-assembly and their structures analyzed using the sine trigonometric function.Slow evaporation of a methylene chloride-methanol solution of a 1:1 molar mixture of [M(tmhd)₂], where M = Co or Ni, and quinoxaline; a 1:2:1 molar mixture of [M(acac)₂], where M = Co or Ni, 2,2,6,6-tetramethyl-3,5-heptadione and quinoxaline; or a 1:2:1 molar mixture of [Co(acac)₂], dibenzoylmethane, and quinoxaline, yielded the crystalline coordination polymers. In the presence of the nitrogenous base, ligand scrambling occurs yielding the most insoluble product. The synthesis and structures of the following wavelike polymers are reported: trans-[Co(DBM)₂(qox)]_n·nH₂O (2), trans-[Co(tmhd)₂(qox)]_n(3), trans-[Ni(tmhd)₂(qox)]_n (4), where DBM⁻= dibenzoylmethanate, tmhd⁻= 2,2,6,6-tetramethyl-3,5-heptadionate, and qox = quinoxaline. The wavelike structures are generated by intramolecular steric interactions and crystal packing forces between the chains. Some of the tert-butyl groups show a two-fold disorder. The sine function, φ = A sin 2πx/λ, where φ = distance (Ǻ) along the polymer backbone, λ = wavelength (Ǻ), A = amplitude (Ǻ), x = distance (Ǻ) along the polymer axis, provides a method to approximate and visualize the polymer structures. Full article

(This article belongs to the Special Issue Coordination Polymers)

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Graphical abstract

11 pages, 412 KiB

Open AccessArticle

Metal-Free Polymethyl Methacrylate (PMMA) Nanoparticles by Enamine “Click” Chemistry at Room Temperature

by Lorea Buruaga¹ and José A. Pomposo^1,2,3,*

¹ Centro de Física de Materiales (CSIC, UPV/EHU) - Materials Physics Center, Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain

² Departamento de Física de Materiales, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20800 San Sebastián, Spain

³ IKERBASQUE - Basque Foundation for Science, Alameda Urquijo 36, 48011 Bilbao, Spain

Polymers 2011, 3(4), 1673-1683; https://doi.org/10.3390/polym3041673 - 7 Oct 2011

Cited by 29 | Viewed by 10739

Abstract

“Click” chemistry has become an efficient avenue to unimolecular polymeric nanoparticles through the self-crosslinking of individual polymer chains containing appropriate functional groups. Herein we report the synthesis of ultra-small (7 nm in size) polymethyl methacrylate (PMMA) nanoparticles (NPs) by the “metal-free” cross-linking of [...] Read more.

“Click” chemistry has become an efficient avenue to unimolecular polymeric nanoparticles through the self-crosslinking of individual polymer chains containing appropriate functional groups. Herein we report the synthesis of ultra-small (7 nm in size) polymethyl methacrylate (PMMA) nanoparticles (NPs) by the “metal-free” cross-linking of PMMA-precursor chains prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization containing b-ketoester functional groups. Intramolecular collapse was performed by the one-pot reaction of b-ketoester moieties with alkyl diamines in tetrahydrofurane at r.t. (i.e., by enamine formation). The collapsing process was followed by size exclusion chromatography and by nuclear magnetic resonance spectroscopy. The size of the resulting PMMA-NPs was determined by dynamic light scattering. Enamine “click” chemistry increases the synthetic toolbox for the efficient synthesis of metal-free, ultra-small polymeric NPs. Full article

(This article belongs to the Special Issue Click Chemistry in Polymer Science)

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50 pages, 2313 KiB

Open AccessReview

Biodegradable Cell-Seeded Nanofiber Scaffolds for Neural Repair

by Dong Han^* and Karen C. Cheung

Department of Electrical and Computer Engineering, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada

Polymers 2011, 3(4), 1684-1733; https://doi.org/10.3390/polym3041684 - 10 Oct 2011

Cited by 39 | Viewed by 12232

Abstract

Central and peripheral neural injuries are traumatic and can lead to loss of motor and sensory function, chronic pain, and permanent disability. Strategies that bridge the site of injury and allow axonal regeneration promise to have a large impact on restoring quality of [...] Read more.

Central and peripheral neural injuries are traumatic and can lead to loss of motor and sensory function, chronic pain, and permanent disability. Strategies that bridge the site of injury and allow axonal regeneration promise to have a large impact on restoring quality of life for these patients. Engineered materials can be used to guide axonal growth. Specifically, nanofiber structures can mimic the natural extracellular matrix, and aligned nanofibers have been shown to direct neurite outgrowth and support axon regeneration. In addition, cell-seeded scaffolds can assist in the remyelination of the regenerating axons. The electrospinning process allows control over fiber diameter, alignment, porosity, and morphology. Biodegradable polymers have been electrospun and their use in tissue engineering has been demonstrated. This paper discusses aspects of electrospun biodegradable nanofibers for neural regeneration, how fiber alignment affects cell alignment, and how cell-seeded scaffolds can increase the effectiveness of such implants. Full article

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16 pages, 954 KiB

Open AccessArticle

Effect of Compatibilization on Poly-ε-Caprolactone Grafting onto Poly(ethylene-co-vinyl alcohol)

by Samira Touhtouh^1,2,3, Frederic Becquart^1,2,3, Caroline Pillon^1,2,3 and Mohamed Taha^1,2,3,*

¹ Université de Lyon, F-42023, Saint Etienne, France

² CNRS, UMR 5223, Ingénierie des Matériaux Polymères, 42023, Saint-Etienne, France

³ IMP@UJM, Université de Saint-Etienne, Jean Monnet, F-42023, Saint-Etienne, France

Polymers 2011, 3(4), 1734-1749; https://doi.org/10.3390/polym3041734 - 11 Oct 2011

Cited by 10 | Viewed by 7713

Abstract

The non-miscibility of the reactants during solvent free poly-ε-caprolactone grafting onto poly(ethylene-co-vinyl alcohol) (EVOH) dramatically affects reaction kinetics. Different solutions were proposed to accelerate the exchange reactions between poly(ethylene-co-vinyl alcohol) and poly-ε-caprolactone. Reactions were conducted in a batch reactor [...] Read more.

The non-miscibility of the reactants during solvent free poly-ε-caprolactone grafting onto poly(ethylene-co-vinyl alcohol) (EVOH) dramatically affects reaction kinetics. Different solutions were proposed to accelerate the exchange reactions between poly(ethylene-co-vinyl alcohol) and poly-ε-caprolactone. Reactions were conducted in a batch reactor or a mini twin-screw extruder. The addition of a poly(ethylene-co-vinyl alcohol)-g-poly-ε-caprolactone copolymer increased the compatibility of the reactants and led to a higher reaction rate. This copolymer was either prepared separately and added at the reaction beginning or prepared in situ grafting caprolactone from EVOH. The reactive system evolution was analyzed using molar mass evolution, microstructure characterization, thermal properties and the reactive blend morphology. The compatibilization effect combined with optimized reaction conditions, such as concentration and nature of catalyst and temperature, resulted in an important increase in reaction rates. Among the tested catalysts, 1,5,7-Triazabicyclo [4.4.0]dec-5-ene was a more efficient catalyst for grafting reactions than Tin (II) 2-ethylhexanoate. Full article

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26 pages, 4018 KiB

Open AccessReview

Coordination Polymers and Metal Organic Frameworks Derived from 1,2,4-Triazole Amino Acid Linkers

by Anil D. Naik, Marinela M. Dîrtu, Antoine P. Railliet, Jacqueline Marchand-Brynaert and Yann Garcia^*

Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium

Polymers 2011, 3(4), 1750-1775; https://doi.org/10.3390/polym3041750 - 11 Oct 2011

Cited by 59 | Viewed by 13922

Abstract

The perceptible appearance of biomolecules as prospective building blocks in the architecture of coordination polymers (CPs) and metal-organic frameworks (MOFs) are redolent of their inclusion in the synthon/tecton library of reticular chemistry. In this frame, for the first time a synthetic strategy has [...] Read more.

The perceptible appearance of biomolecules as prospective building blocks in the architecture of coordination polymers (CPs) and metal-organic frameworks (MOFs) are redolent of their inclusion in the synthon/tecton library of reticular chemistry. In this frame, for the first time a synthetic strategy has been established for amine derivatization in amino acids into 1,2,4-triazoles. A set of novel 1,2,4-triazole derivatized amino acids were introduced as superlative precursors in the design of 1D coordination polymers, 2D chiral helicates and 3D metal-organic frameworks. Applications associated with these compounds are diverse and include gas adsorption-porosity partitioning, soft sacrificial matrix for morphology and phase selective cadmium oxide synthesis, Fe^II spin crossover materials, zinc-b-lactamases inhibitors, logistics for generation of chiral/non-centrosymmetric networks; and thus led to a foundation of a new family of functional CPs and MOFs that are reviewed in this invited contribution. Full article

(This article belongs to the Special Issue Coordination Polymers)

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Graphical abstract

18 pages, 1103 KiB

Open AccessReview

Regeneration Approaches for Dental Pulp and Periapical Tissues with Growth Factors, Biomaterials, and Laser Irradiation

by Chiaki Kitamura^1,*, Tatsuji Nishihara², Masamichi Terashita³, Yasuhiko Tabata⁴, Eijiro Jimi⁵, Ayako Washio¹ and Shizu Hirata¹

¹ Division of Pulp Biology, Operative Dentistry, and Endodontics, Department of Cariology and Periodontology, Kyushu Dental College, Manazuru 2-6-1, Kokurakita, Kitakyushu 803 8580, Japan

² Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental College, Manazuru 2-6-1, Kokurakita, Kitakyushu 803-8580, Japan

³ Division of Comprehensive Dentistry, Department of Clinical Communication and Practice, Kyushu Dental College, Manazuru 2-6-1, Kokurakita, Kitakyushu 803-8580, Japan

⁴ Department of Biomaterials, Institute for Frontier Medical Sciences, Kyoto University, 53 Kawara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan

⁵ Division of Molecular Signaling and Biochemistry, Department of Biosciences, Kyushu Dental College, Manazuru 2-6-1, Kokurakita, Kitakyushu 803-8580, Japan

Polymers 2011, 3(4), 1776-1793; https://doi.org/10.3390/polym3041776 - 12 Oct 2011

Cited by 17 | Viewed by 14500

Abstract

In current dental practice, restorative and endodontic procedures have been developed in an attempt to preserve the vitality of dental pulp after exposure to external stimuli such as caries infection. When damage to dental pulp is reversible, pulp wound healing can proceed, whereas [...] Read more.

In current dental practice, restorative and endodontic procedures have been developed in an attempt to preserve the vitality of dental pulp after exposure to external stimuli such as caries infection. When damage to dental pulp is reversible, pulp wound healing can proceed, whereas irreversible damage induces pathological changes in dental pulp, eventually requiring its removal. Furthermore, dentists sometimes extract non-vital teeth because of severe caries progression, critical size of periapical lesion, and tooth fracture. To overcome the limitations of presently available therapies, it is important to develop regeneration therapy for dental pulp and periapical tissues. In this review, we focus on the regeneration of dental pulp and periapical tissues by application of exogenous growth factors and scaffolds, as well as low-intensity laser irradiation as an auxiliary therapy for regeneration therapy. Full article

(This article belongs to the Special Issue Polymers for Oro-Dental and Cranio- Maxillo-Facial Applications)

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11 pages, 428 KiB

Open AccessArticle

Dependence of Optical and Microstructure Properties of Thiol-Capped Silver Nanoparticles Embedded in Polymeric Matrix

by Angela Longo^1,*, Gianfranco Carotenuto¹

, Mariano Palomba¹ and Sergio De Nicola²

¹ Institute for Composite and Biomedical Materials, National Research Council (IMCB-CNR), P.le Tecchio 80, 80125 Naples, Italy

² National Institute of Optics, National Research Council (INO-CNR), Viale Campi Flegrei 34, 80078 Pozzuoli, Italy

Polymers 2011, 3(4), 1794-1804; https://doi.org/10.3390/polym3041794 - 13 Oct 2011

Cited by 21 | Viewed by 8395

Abstract

Thiol-capped silver nanoparticles were prepared by in situ thermal decomposition of different silver(I)-thiolates precursors in a polymeric matrix. Depending on the structure of the organic coating, contact-free distribution of metal nanoparticles or nanoparticles aggregates were achieved. The structure and morphology of nanocomposites was [...] Read more.

Thiol-capped silver nanoparticles were prepared by in situ thermal decomposition of different silver(I)-thiolates precursors in a polymeric matrix. Depending on the structure of the organic coating, contact-free distribution of metal nanoparticles or nanoparticles aggregates were achieved. The structure and morphology of nanocomposites was analyzed by Transmission Electron Microscopy (TEM), and X-Ray Diffraction (XRD). Nanoparticles’ interaction was investigated by differential scanning calorimetry (DSC), and UV-Visible spectroscopy. In particular, only silver nanoparticles coated by n-alkyl thiols aggregated, while a contact-free dispersion was obtained by cyclohexyl thiol-capped silver nanoparticles. Full article

(This article belongs to the Special Issue Polymers for Optical Applications)

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28 pages, 1294 KiB

Open AccessArticle

Polymer and Water Dynamics in Poly(vinyl alcohol)/Poly(methacrylate) Networks. A Molecular Dynamics Simulation and Incoherent Neutron Scattering Investigation

by Gaio Paradossi¹, Ivana Finelli¹, Francesca Natali², Mark T. F. Telling^3,4 and Ester Chiessi^1,*

¹ Department of Chemical Sciences and Technologies, University of Rome Tor Vergata, Via della Ricerca Scientifica 000133 Rome, Italy

² CNR OGG and CRS-SOFT, c/o ILL, 6 Rue Jules Horowitz, BP 156-38042 Grenoble, France

³ Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK

⁴ ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, OX11 OQX, UK

Polymers 2011, 3(4), 1805-1832; https://doi.org/10.3390/polym3041805 - 17 Oct 2011

Cited by 21 | Viewed by 11743

Abstract

Chemically cross-linked polymer networks of poly(vinyl alcohol)/poly(methacrylate) form monolitic hydrogels and microgels suitable for biomedical applications, such as in situ tissue replacement and drug delivery. In this work, molecular dynamics (MD) simulation and incoherent neutron scattering methods are used to study the local [...] Read more.

Chemically cross-linked polymer networks of poly(vinyl alcohol)/poly(methacrylate) form monolitic hydrogels and microgels suitable for biomedical applications, such as in situ tissue replacement and drug delivery. In this work, molecular dynamics (MD) simulation and incoherent neutron scattering methods are used to study the local polymer dynamics and the polymer induced modification of water properties in poly(vinyl alcohol)/poly(methacrylate) hydrogels. This information is particularly relevant when the diffusion of metabolites and drugs is a requirement for the polymer microgel functionality. MD simulations of an atomic detailed model of the junction domain at the experimental hydration degree were carried out at 283, 293 and 313 K. The polymer-water interaction, the polymer connectivity and the water dynamics were investigated as a function of temperature. Simulation results are compared with findings of elastic and quasi-elastic incoherent neutron scattering measurements, experimental approaches which sample the same space-time window of MD simulations. This combined analysis shows a supercooled water component and an increase of hydrophilicity and mobility with temperature of these amphiphilic polymer networks. Full article

(This article belongs to the Special Issue Polymer Nanogels and Microgels)

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Graphical abstract

16 pages, 937 KiB

Open AccessArticle

Gold-Poly(methyl methacrylate) Nanocomposite Films for Plasmonic Biosensing Applications

by Mohammed Alsawafta¹, Simona Badilescu^2,*, Abhilash Paneri², Vo-Van Truong¹ and Muthukumaram Packirisamy²

¹ Physics Department, Concordia University, 1455 de Maisonneuve Blvd. W., Montréal, QC H3G 1M8, Canada

² Mechanical and Industrial Engineering Department, Concordia University, 1455 de Maisonneuve Blvd. W., Montréal, QC H3G 1M8, Canada

Polymers 2011, 3(4), 1833-1848; https://doi.org/10.3390/polym3041833 - 25 Oct 2011

Cited by 61 | Viewed by 10577

Abstract

Gold-poly(methyl methacrylate) nanocomposites are prepared by an in situ method, by irradiating spin-coated films containing the polymer and the gold precursor dissolved in acetone. The reduction of gold ions results in the formation of Au that nucleates and grows within the polymer film. [...] Read more.

Gold-poly(methyl methacrylate) nanocomposites are prepared by an in situ method, by irradiating spin-coated films containing the polymer and the gold precursor dissolved in acetone. The reduction of gold ions results in the formation of Au that nucleates and grows within the polymer film. It is shown that, depending on the energy source, gold nanoparticles with different shapes can be formed. Nanocomposites prepared through UV-, thermal-, and MW-irradiation, respectively, show a low sensitivity toward the environment. However, by annealing the samples at temperatures well above the glass transition temperature of the polymer, the response to dielectric environment appears to be enhanced significantly. The sensitivity of samples synthesized through the three different methods is found to be comparable, around 100 nm/RIU. The increased sensitivity of the annealed sample is accounted for by the increased mobility of both polymer chains and gold nanoparticles in the rubbery state of the material and the presence of the monomer. Gold nanoparticles “freed” from the strong interaction with the polymer are now able to feel the molecules from the surrounding environment. The results show that, by using adequate post-synthesis heat treatments, gold-polymer nanocomposites can be used as plasmonic sensing platforms. Full article

(This article belongs to the Special Issue Polymer-Inorganic Hybrids and Their Applications)

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17 pages, 1124 KiB

Open AccessArticle

Preparation of Novel Hydrolyzing Urethane Modified Thiol-Ene Networks

by Nicole M. Mackey¹, Bridget S. Confait¹, James H. Wynne² and J. Paige Buchanan^1,*,†

¹ Department of Chemistry and Biochemistry, University of Southern Mississippi, 118 College Drive, Hattiesburg, MS 39406, USA

² Chemistry Division, Naval Research Laboratory, 4555 Overlook Ave, SW, Washington, DC 20375, USA

^† J. Paige Buchanan was formerly known as J. Paige Phillips.

Polymers 2011, 3(4), 1849-1865; https://doi.org/10.3390/polym3041849 - 25 Oct 2011

Cited by 4 | Viewed by 10707

Abstract

Novel tetra-functional hydrolyzing monomers were prepared from the reaction of TEOS and select alkene-containing alcohols, ethylene glycol vinyl ether or 2-allyloxy ethanol, and combined with trimethylolpropane tris(3-mercaptopropionate) (tri-thiol) in a thiol-ene “click” polymerization reaction to produce clear, colorless thiol-ene networks using both radiation [...] Read more.

Novel tetra-functional hydrolyzing monomers were prepared from the reaction of TEOS and select alkene-containing alcohols, ethylene glycol vinyl ether or 2-allyloxy ethanol, and combined with trimethylolpropane tris(3-mercaptopropionate) (tri-thiol) in a thiol-ene “click” polymerization reaction to produce clear, colorless thiol-ene networks using both radiation and thermal-cure techniques. These networks were characterized for various mechanical characteristics, and found to posses T_g’s (DSC), hardness, tack, and thermal stability (TGA) consistent with their molecular structures. A new ene-modified urethane oligomer was prepared based on the aliphatic polyisocyanate Desmodur^®N 3600 and added to the thiol-ene hydrolyzable network series in increasing amounts, creating a phase-segregated material having two T_g’s. An increase in water absorption in the ene-modified urethane formulations leading to a simultaneous increase in the rate of hydrolysis was supported by TGA data, film hardness measurements, and an NMR study of closely related networks. This phenomenon was attributed to the additional hydrogen bonding elements and polar functionality brought to the film with the addition of the urethane segment. SEM was utilized for visual analysis of topographical changes in the film’s surface upon hydrolysis and provides support for surface-driven erosion. Coatings prepared in this study are intended for use as hydrolyzing networks for marine coatings to protect against ship fouling. Full article

(This article belongs to the Special Issue Click Chemistry in Polymer Science)

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9 pages, 349 KiB

Open AccessArticle

One-Dimensional Helical Homochiral Metal-Organic Framework Built from 2,2′-Dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic Acid

by Koichi Tanaka^1,*, Yuki Kikumoto¹ and Motoo Shiro²

¹ Department of Chemistry and Materials Engineering, Faculty of Chemistry, Materials and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan

² Rigaku X-ray Laboratory, 3-9-12 Matsubara-cho, Akishima, Tokyo 196-8666, Japan

Polymers 2011, 3(4), 1866-1874; https://doi.org/10.3390/polym3041866 - 1 Nov 2011

Cited by 3 | Viewed by 8099

Abstract

A homochiral metal-organic framework (MOF) based on enantiopure (R)-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid was synthesized. X-ray crystal diffraction studies revealed that the MOF adopts a one-dimensional infinite right-handed helical tubular structure along the a-axis, which serves as a host for the inclusion of [...] Read more.

A homochiral metal-organic framework (MOF) based on enantiopure (R)-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxylic acid was synthesized. X-ray crystal diffraction studies revealed that the MOF adopts a one-dimensional infinite right-handed helical tubular structure along the a-axis, which serves as a host for the inclusion of guest dimethylformamide (DMF) molecules. Full article

(This article belongs to the Special Issue Coordination Polymers)

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27 pages, 607 KiB

Open AccessReview

Biomedical Activity of Chitin/Chitosan Based Materials—Influence of Physicochemical Properties Apart from Molecular Weight and Degree of N-Acetylation

by Jolanta Kumirska^1,*, Mirko X. Weinhold², Jorg Thöming²

and Piotr Stepnowski¹

¹ Faculty of Chemistry, University of Gdansk, Sobieskiego 18/19, PL-80-952 Gdansk, Poland

² UFT—Centre for Environmental Research and Sustainable Technology, University of Bremen, Leobener Straße UFT, D-28359 Bremen, Germany

Polymers 2011, 3(4), 1875-1901; https://doi.org/10.3390/polym3041875 - 3 Nov 2011

Cited by 257 | Viewed by 23133

Abstract

The physicochemical nature of chitin and chitosan, which influences the biomedical activity of these compounds, is strongly related to the source of chitin and the conditions of the chitin/chitosan production process. Apart from widely described key factors such as weight-averaged molecular weight (M [...] Read more.

The physicochemical nature of chitin and chitosan, which influences the biomedical activity of these compounds, is strongly related to the source of chitin and the conditions of the chitin/chitosan production process. Apart from widely described key factors such as weight-averaged molecular weight (M_W) and degree of N-acetylation (DA), other physicochemical parameters like polydispersity (M_W/M_N), crystallinity or the pattern of acetylation (P_A) have to be taken into consideration. From the biological point of view, these parameters affect a very important factor—the solubility of chitin and chitosan in water and organic solvents. The physicochemical properties of chitosan solutions can be controlled by manipulating solution conditions (temperature, pH, ionic strength, concentration, solvent). The degree of substitution of the hydroxyl and the amino groups or the degree of quaternization of the amino groups also influence the mechanical and biological properties of chitosan samples. Finally, a considerable research effort has been directed towards developing safe and efficient chitin/chitosan-based products because many factors, like the size of nanoparticles, can determine the biomedical characteristics of medicinal products. The influence of these factors on the biomedical activity of chitin/chitosan-based products is presented in this report in more detail. Full article

(This article belongs to the Collection Polysaccharides)

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9 pages, 221 KiB

Open AccessCommunication

Bacterial Inactivation Kinetics of Dialdehyde Starch Aqueous Suspension

by Le Song¹, Samuel R. Farrah² and Ronald H. Baney^1,*

¹ Department of Materials and Science and Engineering, University of Florida, Gainesville, FL 32611, USA

² Department of Microbiology and Cell Sciences, University of Florida, Gainesville, FL 32611, USA

Polymers 2011, 3(4), 1902-1910; https://doi.org/10.3390/polym3041902 - 3 Nov 2011

Cited by 14 | Viewed by 7722

Abstract

The bacterial inactivation kinetics of dialdehyde starch (DAS) aqueous suspension was studied by the relationship between the minimal lethal concentration (MLC) and the inactivation time at four different temperatures. The relationship between MLC and exposure time was found to follow the first-order Chick-Watson [...] Read more.

The bacterial inactivation kinetics of dialdehyde starch (DAS) aqueous suspension was studied by the relationship between the minimal lethal concentration (MLC) and the inactivation time at four different temperatures. The relationship between MLC and exposure time was found to follow the first-order Chick-Watson law. This first-order inactivation kinetics was modeled by pseudo-first order chemical reaction. This model was validated by the successful predication of the bacterial inactivation response at room temperature. Full article

(This article belongs to the Collection Polysaccharides)

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23 pages, 1940 KiB

Open AccessReview

Water-Soluble Stimuli Responsive Star-Shaped Segmented Macromolecules

by Zacharoula Iatridi¹

and Constantinos Tsitsilianis^1,2,*

¹ Department of Chemical Engineering, University of Patras, 26504 Patras, Greece

² Institute of Chemical Engineering and High Temperature Chemical Processes ICE/HT-FORTH, P.O. Box 1414, 26504 Patras, Greece

Polymers 2011, 3(4), 1911-1933; https://doi.org/10.3390/polym3041911 - 3 Nov 2011

Cited by 60 | Viewed by 14890

Abstract

Star shaped segmented macromolecules constitute an interesting class of polymeric materials whose properties differ remarkably from those appearing in their linear counterparts. This review highlights the work done in the last decade, dealing with the self-assembly of star-shaped block copolymers and terpolymers of [...] Read more.

Star shaped segmented macromolecules constitute an interesting class of polymeric materials whose properties differ remarkably from those appearing in their linear counterparts. This review highlights the work done in the last decade, dealing with the self-assembly of star-shaped block copolymers and terpolymers of various topologies in aqueous media. This article focuses on a specific class of star shaped macromolecules designated as stimuli responsive. These stars bearblock/arms undergo sharp phase transitions upon responding to stimuli, such as temperature, pH, ionic strength and so forth. These transitions impose dramatic transformations on the morphology and, accordingly, in the functionality of the nanostructured associates. The number of arms, the specific functionality and topology of the different arm/blocks and the overall macromolecular architecture of the star polymer, significantly influence their behavior in terms of self-assembly and responsiveness. Full article

(This article belongs to the Special Issue Water-Soluble Polymers)

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10 pages, 682 KiB

Open AccessArticle

Synthesis and Characterization of Novel Copper(II) 2D Coordination Polymers from a Fluorinated Flexible Ligand with Remarkable Clathration Ability

by Tomohiro Beni and Kayoko Kasai^*

Department of Science Education, Miyagi University of Education, 149 Aoba, Aramaki, Aoba-ku, Sendai 980-0845, Japan

Polymers 2011, 3(4), 1934-1943; https://doi.org/10.3390/polym3041934 - 7 Nov 2011

Viewed by 6334

Abstract

Two-dimensional (2D) grid coordination polymers were prepared by the reaction of 1,4-bis(4-pyridylmethyl)tetrafluorobenzene (bpf) with Cu(NO₃)₂ in the presence of aromatic compounds. Crystal structures of {[Cu(bpf)₂(NO₃)₂]·(biphenyl)₂}_n (1), {[Cu(bpf)₂(NO [...] Read more.

Two-dimensional (2D) grid coordination polymers were prepared by the reaction of 1,4-bis(4-pyridylmethyl)tetrafluorobenzene (bpf) with Cu(NO₃)₂ in the presence of aromatic compounds. Crystal structures of {[Cu(bpf)₂(NO₃)₂]·(biphenyl)₂}_n (1), {[Cu(bpf)₂(NO₃)₂]·(m-C₆H₄(OMe)₂)₂}_n (2), {[Cu(bpf)₂(NO₃)₂]·Ph^tBu}_n (3) and {[Cu(bpf)₂(NO₃)(H₂O)]NO₃·(bpf)_0.5}_n (4) were determined. The grid networks were held together by C–H···O and C–H···F hydrogen bonds via the NO₃⁻ anions and the tetrafluorophenylene rings of bpf, respectively. Biphenyl, m-dimethoxybenzene, t-butylbenzene, and bpf molecules were clathrated in cyclic cavities of the grid networks through arene-perfluoroarene interactions. These coordination networks have remarkable clathration ability for aromatic compounds. Full article

(This article belongs to the Special Issue Coordination Polymers)

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28 pages, 849 KiB

Open AccessArticle

Threshold Particle Diameters in Miniemulsion Reversible-Deactivation Radical Polymerization

by Hidetaka Tobita

Department of Materials Science and Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 901-8507, Japan

Polymers 2011, 3(4), 1944-1971; https://doi.org/10.3390/polym3041944 - 11 Nov 2011

Cited by 13 | Viewed by 7021

Abstract

Various types of controlled/living radical polymerizations, or using the IUPAC recommended term, reversible-deactivation radical polymerization (RDRP), conducted inside nano-sized reaction loci are considered in a unified manner, based on the polymerization rate expression, R_p= k_p[M]K[Interm]/[ [...] Read more.

Various types of controlled/living radical polymerizations, or using the IUPAC recommended term, reversible-deactivation radical polymerization (RDRP), conducted inside nano-sized reaction loci are considered in a unified manner, based on the polymerization rate expression, R_p= k_p[M]K[Interm]/[Trap]. Unique miniemulsion polymerization kinetics of RDRP are elucidated on the basis of the following two factors: (1) A high single molecule concentration in a nano-sized particle; and (2) a significant statistical concentration variation among particles. The characteristic particle diameters below which the polymerization rate start to deviate significantly (1) from the corresponding bulk polymerization, and (2) from the estimate using the average concentrations, can be estimated by using simple equations. For stable-radical-mediated polymerization (SRMP) and atom-transfer radical polymerization (ATRP), an acceleration window is predicted for the particle diameter range, . For reversible-addition-fragmentation chain-transfer polymerization (RAFT), degenerative-transfer radical polymerization (DTRP) and also for the conventional nonliving radical polymerization, a significant rate increase occurs for . On the other hand, for the polymerization rate is suppressed because of a large statistical variation of monomer concentration among particles. Full article

(This article belongs to the Special Issue Living Polymerization Techniques)

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38 pages, 506 KiB

Open AccessReview

Water Soluble Polymers for Pharmaceutical Applications

by Veeran Gowda Kadajji and Guru V. Betageri^*

Department of Pharmaceutical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA

Polymers 2011, 3(4), 1972-2009; https://doi.org/10.3390/polym3041972 - 11 Nov 2011

Cited by 514 | Viewed by 74062

Abstract

Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers [...] Read more.

Advances in polymer science have led to the development of novel drug delivery systems. Some polymers are obtained from natural resources and then chemically modified for various applications, while others are chemically synthesized and used. A large number of natural and synthetic polymers are available. In the present paper, only water soluble polymers are described. They have been explained in two categories (1) synthetic and (2) natural. Drug polymer conjugates, block copolymers, hydrogels and other water soluble drug polymer complexes have also been explained. The general properties and applications of different water soluble polymers in the formulation of different dosage forms, novel delivery systems and biomedical applications will be discussed. Full article

(This article belongs to the Special Issue Water-Soluble Polymers)

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8 pages, 173 KiB

Open AccessReview

Role of Antimicrobial Peptides in Inflammatory Bowel Disease

by Jan-Michel Otte^1,* and Stefan Vordenbäumen²

¹ Department of Internal Medicine I, St. Josef-Hospital, Ruhr-University, Gudrunstr. 56, 44791 Bochum, Germany

² Department of Endocrinology, Diabetology and Rheumatology, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany

Polymers 2011, 3(4), 2010-2017; https://doi.org/10.3390/polym3042010 - 16 Nov 2011

Cited by 15 | Viewed by 7052

Abstract

Inflammatory bowel diseases (IBD) are characterized by a chronic relapsing inflammation of the gastrointestinal mucosa. The etiology and pathogenesis of these disorders such as Crohn’s disease and ulcerative colitis are incompletely understood. Recently, antimicrobial peptides, which are expressed by leukocytes and epithelia, have [...] Read more.

Inflammatory bowel diseases (IBD) are characterized by a chronic relapsing inflammation of the gastrointestinal mucosa. The etiology and pathogenesis of these disorders such as Crohn’s disease and ulcerative colitis are incompletely understood. Recently, antimicrobial peptides, which are expressed by leukocytes and epithelia, have been implicated in the pathogenesis of IBD. Antimicrobial peptides are pivotal for intestinal defense, shaping the composition of the luminal flora and contributing thereby to the maintenance of intestinal homeostasis. Apart from their antimicrobial activity affecting commensal bacteria, immunomodulatory properties of antimicrobial peptides have been identified, which link innate and adaptive immune response. There is increasing evidence that alterations in mucosal levels of these peptides contribute to IBD pathogenensis. Full article

(This article belongs to the Special Issue Antibacterial Polymers: From Natural Inspiration to Practical Applications)

21 pages, 1091 KiB

Open AccessArticle

Incorporation of Hyperbranched Supramolecules into Nafion Ionic Domains via Impregnation and In-Situ Photopolymerization

by Nadzrinahamin A. Nazir¹, Thein Kyu^1,*, Anna M. Reinsel², Matthew Espe², Mami Nosaka³, Hiruto Kudo³ and Tadatomi Nishikubo³

¹ Department of Polymer Engineering, University of Akron, Akron, OH 44325, USA

² Department of Chemistry, University of Akron, Akron, OH 44325, USA

³ Department of Applied Chemistry, Kanagawa University, Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

Polymers 2011, 3(4), 2018-2038; https://doi.org/10.3390/polym3042018 - 28 Nov 2011

Cited by 20 | Viewed by 11943

Abstract

Nafion membranes were impregnated with photocurable supramolecules, viz., hyperbranched polyester having pendant functional carboxylic acid groups (HBPEAc-COOH) by swelling in methanol and subsequently photocured in-situ after drying. Structure-property relationships of the HBPEAc-COOH impregnated Nafion membranes were analyzed on the basis of Fourier transform [...] Read more.

Nafion membranes were impregnated with photocurable supramolecules, viz., hyperbranched polyester having pendant functional carboxylic acid groups (HBPEAc-COOH) by swelling in methanol and subsequently photocured in-situ after drying. Structure-property relationships of the HBPEAc-COOH impregnated Nafion membranes were analyzed on the basis of Fourier transform infrared (FTIR) spectroscopy, solid-state nuclear magnetic resonance (SSNMR) and dynamic mechanical analysis (DMA). FTIR and SSNMR investigations revealed that about 7 wt % of HBPEAc-COOH was actually incorporated into the ionic domains of Nafion. The FTIR study suggests possible complexation via inter-species hydrogen bonding between the carboxylic groups of HBPEAc-COOH and the sulfonate groups of Nafion. The α-relaxation peak corresponding to the glass transition temperature of the ionic domains of the neat Nafion-acid form was found to increase from ~100 to ~130 °C upon impregnation with enhanced modulus afforded by the cured polyester network within the ionic domains. The AC impedance fuel cell measurement of the impregnated membrane exhibited an increasing trend of proton conductivity with increasing temperature, which eventually surpassed that of neat Nafion above 100 °C. Of particular importance is that the present paper is the first to successfully incorporate polymer molecules/networks into the Nafion ionic domains by means of impregnation with hyperbranched supramolecules followed by in-situ photopolymerization. Full article

(This article belongs to the Special Issue Dendrimers and Hyperbranched Polymers)

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14 pages, 815 KiB

Open AccessArticle

The Influence of Synthesis Parameters on Particle Size and Photoluminescence Characteristics of Ligand Capped Tb³⁺:LaF₃

by Kyle Gipson¹, Courtney Kucera¹, Derek Stadther², Kathryn Stevens¹, John Ballato¹ and Phil Brown^1,*

¹ Center for Optical Materials Science & Engineering Technologies (COMSET), School of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA

² Department of Physics, Furman University, Greenville, SC 29613, USA

Polymers 2011, 3(4), 2039-2052; https://doi.org/10.3390/polym3042039 - 29 Nov 2011

Cited by 12 | Viewed by 8232

Abstract

Organic ligand surface-treated Tb³⁺:LaF₃ was synthesized in water and methanol for subsequent incorporation into polymethyl methacrylate (PMMA) via solution-precipitation chemistry in order to produce optically active polymer nanocomposites. Nanoparticle agglomerate diameters ranged from 388 ± 188 nm when synthesized in [...] Read more.

Organic ligand surface-treated Tb³⁺:LaF₃ was synthesized in water and methanol for subsequent incorporation into polymethyl methacrylate (PMMA) via solution-precipitation chemistry in order to produce optically active polymer nanocomposites. Nanoparticle agglomerate diameters ranged from 388 ± 188 nm when synthesized in water and 37 ± 2 nm when synthesized in methanol. Suspension stability is paramount for producing optically transparent materials. Methanol nanoparticle synthesized at a pH of 3 exhibited the smallest agglomerate size. Optical spectroscopy, dynamic light scattering, transmission electron microscopy, scanning transmission electron microscopy, and zeta potential analysis were used to characterize the particles synthesized. Full article

(This article belongs to the Special Issue Polymers for Optical Applications)

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25 pages, 764 KiB

Open AccessReview

Mechanisms of Light Energy Harvesting in Dendrimers and Hyperbranched Polymers

by David S. Bradshaw and David L. Andrews^*

School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK

Polymers 2011, 3(4), 2053-2077; https://doi.org/10.3390/polym3042053 - 5 Dec 2011

Cited by 34 | Viewed by 9808

Abstract

Since their earliest synthesis, much interest has arisen in the use of dendritic and structurally allied forms of polymer for light energy harvesting, especially as organic adjuncts for solar energy devices. With the facility to accommodate a proliferation of antenna chromophores, such materials [...] Read more.

Since their earliest synthesis, much interest has arisen in the use of dendritic and structurally allied forms of polymer for light energy harvesting, especially as organic adjuncts for solar energy devices. With the facility to accommodate a proliferation of antenna chromophores, such materials can capture and channel light energy with a high degree of efficiency, each polymer unit potentially delivering the energy of one photon—or more, when optical nonlinearity is involved. To ensure the highest efficiency of operation, it is essential to understand the processes responsible for photon capture and channelling of the resulting electronic excitation. Highlighting the latest theoretical advances, this paper reviews the principal mechanisms, which prove to involve a complex interplay of structural, spectroscopic and electrodynamic properties. Designing materials with the capacity to capture and control light energy facilitates applications that now extend from solar energy to medical photonics. Full article

(This article belongs to the Special Issue Dendrimers and Hyperbranched Polymers)

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10 pages, 1555 KiB

Open AccessCommunication

Embryonic Stem Cells Maintain an Undifferentiated State on Dendrimer-Immobilized Surface with d-Glucose Display

by Shohreh Mashayekhan^1,*, Mee-Hae Kim², Masahiro Kino-oka², Jun-ichi Miyazaki³ and Masahito Taya⁴

¹ Department of Chemical & Petroleum Engineering, Sharif University of Technology, Azadi Ave, Tehran, 11365-8639, Iran

² Laboratory of BioProcess Systems Engineering, Department of Biotechnology, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan

³ Division of Stem Cell Regulation Research (G6), Graduate School of Medicine, Osaka University, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan

⁴ Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama-cho, Toyonaka, Osaka, 560-8531, Japan

Polymers 2011, 3(4), 2078-2087; https://doi.org/10.3390/polym3042078 - 5 Dec 2011

Cited by 1 | Viewed by 7143

Abstract

In serial passaging cultures of mouse embryonic stem (ES) cells, we employed a dendrimer-immobilized substrate that displayed d-glucose as a terminal ligand. The d-glucose-displaying dendrimer (GLU/D) surface caused the ES cells to form loosely attached spherical colonies, while those on a gelatin-coated surface [...] Read more.

In serial passaging cultures of mouse embryonic stem (ES) cells, we employed a dendrimer-immobilized substrate that displayed d-glucose as a terminal ligand. The d-glucose-displaying dendrimer (GLU/D) surface caused the ES cells to form loosely attached spherical colonies, while those on a gelatin-coated surface formed flatter colonies that were firmly attached to the surface. Despite the morphological similarities between the colonies on the GLU/D surface and aggregates on a conventional bacteriological dish, immunostaining and RT-PCR analyses revealed the maintenance of cells within the spherical colonies on the GLU/D surface in an undifferentiated state with very low expressions of primitive endoderm markers. On the bacteriological dish, however, the cells within the aggregates showed a different cellular state with partial differentiation into the primitive endoderm lineage, and the expression level increased gradually along with the number of passages. These results indicate that the GLU/D surface can be a potential tool for controlling the ES cell morphology and then govern their self-renewal and fate. Full article

(This article belongs to the Special Issue Dendrimers and Hyperbranched Polymers)

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19 pages, 559 KiB

Open AccessArticle

Effects of D-Lysine Substitutions on the Activity and Selectivity of Antimicrobial Peptide CM15

by Heather M. Kaminski and Jimmy B. Feix^*

Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA

Polymers 2011, 3(4), 2088-2106; https://doi.org/10.3390/polym3042088 - 6 Dec 2011

Cited by 29 | Viewed by 7275

Abstract

Despite their potent antimicrobial activity, the usefulness of antimicrobial peptides (AMPs) as antibiotics has been limited by their toxicity to eukaryotic cells and a lack of stability in vivo. In the present study we examined the effects of introducing D-lysine residues into [...] Read more.

Despite their potent antimicrobial activity, the usefulness of antimicrobial peptides (AMPs) as antibiotics has been limited by their toxicity to eukaryotic cells and a lack of stability in vivo. In the present study we examined the effects of introducing D-lysine residues into a 15-residue hybrid AMP containing residues 1–7 of cecropin A and residues 2–9 of melittin (designated CM15). Diastereomeric analogs of CM15 containing between two and five D-lysine substitutions were evaluated for their antimicrobial activity, lysis of human erythrocytes, toxicity to murine macrophages, ability to disrupt cell membranes, and protease stability. All of the analogs caused rapid permeabilization of the Staphylococcus aureus cell envelope, as indicated by uptake of SYTOX green. Permeabilization of the plasma membrane of RAW264.7 macrophages was also observed for CM15, but this was substantially diminished for the D-lysine containing analogs. The introduction of D-lysine caused moderate decreases in antimicrobial activity for all analogs studied, with a much more pronounced reduction in toxicity to eukaryotic cells, leading to marked improvements in antimicrobial efficacy. Circular dichroism studies indicated a progressive loss of helical secondary structure upon introduction of D-lysine residues, with a good correspondence between helical content and eukaryotic cell cytotoxicity. Overall, these studies indicate that disruption of amphipathic secondary structure reduces both antimicrobial activity and eukaryotic cell toxicity, but that the reduction in eukaryotic cell cytotoxicity is more pronounced, leading to an overall gain in antimicrobial selectivity. Full article

(This article belongs to the Special Issue Antibacterial Polymers: From Natural Inspiration to Practical Applications)

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26 pages, 1332 KiB

Open AccessReview

Water Soluble Responsive Polymer Brushes

by Michael P. Weir¹ and Andrew J. Parnell^2,*

¹ Bragg Institute, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia

² Department of Physics and Astronomy, The University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK

Polymers 2011, 3(4), 2107-2132; https://doi.org/10.3390/polym3042107 - 7 Dec 2011

Cited by 38 | Viewed by 12263

Abstract

Responsive polymer brushes possess many interesting properties that enable them to control a range of important interfacial behaviours, including adhesion, wettability, surface adsorption, friction, flow and motility. The ability to design a macromolecular response to a wide variety of external stimuli makes polymer [...] Read more.

Responsive polymer brushes possess many interesting properties that enable them to control a range of important interfacial behaviours, including adhesion, wettability, surface adsorption, friction, flow and motility. The ability to design a macromolecular response to a wide variety of external stimuli makes polymer brushes an exciting class of functional materials, and has been made possible by advances in modern controlled polymerization techniques. In this review we discuss the physics of polymer brush response along with a summary of the techniques used in their synthesis. We then review the various stimuli that can be used to switch brush conformation; temperature, solvent quality, pH and ionic strength as well as the relatively new area of electric field actuation We discuss examples of devices that utilise brush conformational change, before highlighting other potential applications of responsive brushes in real world devices. Full article

(This article belongs to the Special Issue Water-Soluble Polymers)

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9 pages, 632 KiB

Open AccessCommunication

Design of Improved Metal-Organic Framework (MOF) H₂ Adsorbents

by Terumi Furuta^*, Izuru Kanoya, Hiroshi Sakai and Mitsuya Hosoe

Honda R&D Co., Ltd., Fundamental Technology Research Center, 1-4-1 Chuo, Wako-shi, Saitama, 351-0193, Japan

Polymers 2011, 3(4), 2133-2141; https://doi.org/10.3390/polym3042133 - 12 Dec 2011

Cited by 13 | Viewed by 8768

Abstract

We attempted synthesis of the hydrogen adsorption material suitable for the fuel cell vehicles (FCEVs). The designed and synthesized Cu₂(3,5-Pyridinedicarboxylate)₂ (=Cu₂PDC₂) metal complex showed an extremely high volumetric uptake density for a physisorption material, even though [...] Read more.

We attempted synthesis of the hydrogen adsorption material suitable for the fuel cell vehicles (FCEVs). The designed and synthesized Cu₂(3,5-Pyridinedicarboxylate)₂ (=Cu₂PDC₂) metal complex showed an extremely high volumetric uptake density for a physisorption material, even though the specific surface area was only about 1,000 m² g⁻¹. Factors for high uptake properties are considered to be the increased adsorption sites per unit area, the increased adsorption energy, and the optimized design of pore shapes. High hydrogen uptake on volumetric basis is especially effective for FCEV because the tank volume is reduced. It is expected that property prediction using computational simulation and sophisticated analysis at the micro and nano levels will become an indispensable tool in the design of functional materials. Full article

(This article belongs to the Special Issue Coordination Polymers)

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14 pages, 2754 KiB

Open AccessArticle

Plasma Treated Multi-Walled Carbon Nanotubes (MWCNTs) for Epoxy Nanocomposites

by Andrew C. Ritts¹, Qingsong Yu^1,*, Hao Li¹, Stephen J. Lombardo¹, Xu Han¹, Zhenhai Xia² and Jie Lian³

¹ Mechanical and Aerospace Engineering Department, University of Missouri, Lafferre Hall, Columbia, MO 65211, USA

² Department of Material Science and Engineering, University of North Texas, Discovery Park E159A, Denton, TX 76203, USA

³ Department of Mechanical, Aerospace & Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th street, Troy, NY 12180, USA

Polymers 2011, 3(4), 2142-2155; https://doi.org/10.3390/polym3042142 - 19 Dec 2011

Cited by 31 | Viewed by 8673

Abstract

Plasma nanocoating of allylamine were deposited on the surfaces of multi-walled carbon nanotubes (MWCNTs) to provide desirable functionalities and thus to tailor the surface characteristics of MWCNTs for improved dispersion and interfacial adhesion in epoxy matrices. Plasma nanocoated MWCNTs were characterized using scanning [...] Read more.

Plasma nanocoating of allylamine were deposited on the surfaces of multi-walled carbon nanotubes (MWCNTs) to provide desirable functionalities and thus to tailor the surface characteristics of MWCNTs for improved dispersion and interfacial adhesion in epoxy matrices. Plasma nanocoated MWCNTs were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), surface contact angle, and pH change measurements. Mechanical testing results showed that epoxy reinforced with 1.0 wt % plasma coated MWCNTs increased the tensile strength by 54% as compared with the pure epoxy control, while epoxy reinforced with untreated MWCNTs have lower tensile strength than the pure epoxy control. Optical and electron microscopic images show enhanced dispersion of plasma coated MWCNTs in epoxy compared to untreated MWCNTs. Plasma nanocoatings from allylamine on MWCNTs could significantly enhance their dispersion and interfacial adhesion in epoxy matrices. Simulation results based on the shear-lag model derived from micromechanics also confirmed that plasma nanocoating on MWCNTs significantly improved the epoxy/fillers interface bonding and as a result the increased composite strength. Full article

(This article belongs to the Special Issue Polymer-Inorganic Hybrids and Their Applications)

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Polymers, Volume 3, Issue 4 (December 2011) – 32 articles , Pages 1575-2171

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