Polymers

13 pages, 606 KiB

Open AccessArticle

New Insight into Organic Metal Polyaniline Morphology and Structure

by Bernhard Wessling

Ormecon GmbH (a business of Enthone, Inc.), Ferdinand-Harten-Str. 7, D-22949 Ammersbek, Germany

Polymers 2010, 2(4), 786-798; https://doi.org/10.3390/polym2040786 - 17 Dec 2010

Cited by 54 | Viewed by 19572

Polyaniline is known to be a true metal, though a nanometal. Previous experimental and theoretical evidence is reviewed. Two important structural features are presented, which have not publicly been discussed so far: (a) The formation of complexes between polyaniline and metals (Cu, Fe, [...] Read more.

Polyaniline is known to be a true metal, though a nanometal. Previous experimental and theoretical evidence is reviewed. Two important structural features are presented, which have not publicly been discussed so far: (a) The formation of complexes between polyaniline and metals (Cu, Fe, Zn, In, etc.) which are crucial for most practical applications of the organic metal, polyaniline; and (b) a model for the polyaniline chain structure within the smallest morphological unit, the roughly 10 nm primary particle. Full article

(This article belongs to the Special Issue Conductive Polymers)

▼ Show Figures

Figure 1

20 pages, 1068 KiB

Open AccessArticle

Modeling Textural Processes during Self-Assembly of Plant-Based Chiral-Nematic Liquid Crystals

by Yogesh K. Murugesan and Alejandro D. Rey^*

Department of Chemical Engineering, McGill University, 3610, University Street, Montreal, Quebec H3A 2B2, Canada

Polymers 2010, 2(4), 766-785; https://doi.org/10.3390/polym2040766 - 15 Dec 2010

Cited by 25 | Viewed by 9017

Abstract

Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal [...] Read more.

Biological liquid crystalline polymers are found in cellulosic, chitin, and DNA based natural materials. Chiral nematic liquid crystalline orientational order is observed frozen-in in the solid state in plant cell walls and is known as a liquid crystal analogue characterized by a helicoidal plywood architecture. The emergence of the plywood architecture by directed chiral nematic liquid crystalline self assembly has been postulated as the mechanism that leads to optimal cellulose fibril organization. In natural systems, tissue growth and development takes place in the presence of inclusions and secondary phases leaving behind characteristic defects and textures, which provide a unique testing ground for the validity of the liquid crystal self-assembly postulate. In this work, a mathematical model, based on the Landau-de Gennes theory of liquid crystals, is used to simulate defect textures arising in the domain of self assembly, due to presence of secondary phases representing plant cells, lumens and pit canals. It is shown that the obtained defect patterns observed in some plant cell walls are those expected from a truly liquid crystalline phase. The analysis reveals the nature and magnitude of the viscoelastic material parameters that lead to observed patterns in plant-based helicoids through directed self-assembly. In addition, the results provide new guidance to develop biomimetic plywoods for structural and functional applications. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Figure 1

38 pages, 712 KiB

Open AccessReview

Cellulosic Bionanocomposites: A Review of Preparation, Properties and Applications

by Gilberto Siqueira^1,2, Julien Bras¹ and Alain Dufresne^1,*

¹ The International School of Paper, Print Media and Biomaterials (Pagora), Grenoble Institute of Technology, BP 65 - 38402 Saint Martin d'Hères Cedex, France

² Division of Manufacturing and Design of Wood and Bionanocomposites, Luleå University of Technology (LTU) – SE – 97187 Luleå, Sweden

Polymers 2010, 2(4), 728-765; https://doi.org/10.3390/polym2040728 - 13 Dec 2010

Cited by 1178 | Viewed by 47074

Abstract

Cellulose is the most abundant biomass material in nature. Extracted from natural fibers, its hierarchical and multi-level organization allows different kinds of nanoscaled cellulosic fillers—called cellulose nanocrystals or microfibrillated cellulose (MFC)—to be obtained. Recently, such cellulose nanoparticles have been the focus of an [...] Read more.

Cellulose is the most abundant biomass material in nature. Extracted from natural fibers, its hierarchical and multi-level organization allows different kinds of nanoscaled cellulosic fillers—called cellulose nanocrystals or microfibrillated cellulose (MFC)—to be obtained. Recently, such cellulose nanoparticles have been the focus of an exponentially increasing number of works or reviews devoted to understanding such materials and their applications. Major studies over the last decades have shown that cellulose nanoparticles could be used as fillers to improve mechanical and barrier properties of biocomposites. Their use for industrial packaging is being investigated, with continuous studies to find innovative solutions for efficient and sustainable systems. Processing is more and more important and different systems are detailed in this paper depending on the polymer solubility, i.e., (i) hydrosoluble systems, (ii) non-hydrosoluble systems, and (iii) emulsion systems. This paper intends to give a clear overview of cellulose nanoparticles reinforced composites with more than 150 references by describing their preparation, characterization, properties and applications. Full article

(This article belongs to the Collection Polysaccharides)

▼ Show Figures

Figure 1

9 pages, 219 KiB

Open AccessArticle

Preparation and Characterization of Insoluble Silk Fibroin/Chitosan Blend Films

by Mariana Agostini de Moraes, Grinia Michelle Nogueira, Raquel Farias Weska and Marisa Masumi Beppu^*

School of Chemical Engineering, University of Campinas, UNICAMP, 13083-970, Campinas, SP, Brazil

Polymers 2010, 2(4), 719-727; https://doi.org/10.3390/polym2040719 - 13 Dec 2010

Cited by 87 | Viewed by 12409

Abstract

The aim of this study was to prepare and characterize membranes of silk fibroin (SF) and chitosan (CHI) blends. Moreover, a conformation transition of SF to a more stable form induced by the addition of CHI was verified. Blend membranes were prepared, after [...] Read more.

The aim of this study was to prepare and characterize membranes of silk fibroin (SF) and chitosan (CHI) blends. Moreover, a conformation transition of SF to a more stable form induced by the addition of CHI was verified. Blend membranes were prepared, after pH adjustment, in different ratios, and physical integrity, crystallinity, structural conformation and thermal stability were characterized. The results of crystallographic analysis (XRD) indicated the tendency to higher structural organization caused by the addition of CHI. Fourier transformed infrared spectroscopy (FTIR) showed that SF is present in a more stable form in the presence of a CHI content of only 25 wt%. Thermal analysis indicated that SF is thermally stable and that when its proportion in the blend increases, the temperature at which degradation is initiated also increases. Full article

(This article belongs to the Collection Polysaccharides)

▼ Show Figures

Figure 1

10 pages, 108 KiB

Open AccessArticle

Simvastatin Release from Poly(lactide-co-glycolide) Membrane Scaffolds

by Hassan Rashidi¹, Marianne J. Ellis¹, Sarah H. Cartmell²

and Julian B. Chaudhuri^1,*

¹ Centre for Regenerative Medicine, Department of Chemical Engineering, University of Bath, Claverton Down, Bath, BA2 7AY, UK

² School of Materials, Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M13 9PL, UK

Polymers 2010, 2(4), 709-718; https://doi.org/10.3390/polym2040709 - 9 Dec 2010

Cited by 9 | Viewed by 10406

Abstract

Statins, a group of potent inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A reductase in cholesterol biosynthesis pathway, have been widely used as a cholesterol lowering drug. The plieotrophic effect of statins on bone metabolism in long-term usage has been begun to be studied during recent [...] Read more.

Statins, a group of potent inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A reductase in cholesterol biosynthesis pathway, have been widely used as a cholesterol lowering drug. The plieotrophic effect of statins on bone metabolism in long-term usage has been begun to be studied during recent years and several in vitro and in vivo studies have demonstrated the ability of statins to promote expression of bone morphogenetic protein-2 (BMP-2), inhibition of osteoclast differentiation and reduction of osteoporotic fractures risk. The high liver specificity and low oral bioavailability of statins, leading to poor peripheral distribution, are the main obstacles to benefit anabolic effects of hydrophobic statins on bone formation. Therefore, developing new administration roots for direct delivery to achieve optimum concentration in the bone microenvironment is of interest. Here we present and compare two approaches of combining statins with bone tissue engineering scaffolds. Simvastatin was combined with a poly(lactide-co-glycolide) (PLGA) membrane scaffold for diffusion-controlled release by dissolving simvastatin (dis-sim) in the membrane casting dope, and for degradation-controlled release by covalently bonding saponifiedsimvastatin (sap-sim) to the PLGA in the spinning dope. Rheological and concentration-dependent membrane morphology changes were observed with saponifiedsimvastatin, suggesting ester bond cleavage and covalent bonding of the statin to the PLGA, but not with dissolved simvastatin. Dissolved simvastatin membranes showed a logarithmic decay release profile while the saponifiedsimvastatin membranes showed constant release. It can be concluded that the covalent bonding of simvastatinto PLGA scaffolds is showing potential for use as a controlled releasescaffold for bone tissue engineering. Full article

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

▼ Show Figures

Figure 1

19 pages, 3974 KiB

Open AccessArticle

Polyelectrolytes: Influence on Evaporative Self-Assembly of Particles and Assembly of Multilayers with Polymers, Nanoparticles and Carbon Nanotubes

by Irina Marchenko¹, Alexey Yashchenok^2,3, Sergey German², Olga Inozemtseva², Dmitry Gorin^2,3, Tatiana Bukreeva¹, Helmuth Mohwald³ and Andre Skirtach^3,*

¹ Institute of Crystallography, Russian Academy of Sciences, Moscow 119333, Russia

² Saratov State University, Saratov, 410012, Russia

³ Max-Planck Institute of Colloids and Interfaces, Golm, Potsdam, D-14476, Germany

Polymers 2010, 2(4), 690-708; https://doi.org/10.3390/polym2040690 - 9 Dec 2010

Cited by 9 | Viewed by 12647

Abstract

Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte [...] Read more.

Assembling polyelectrolyte multilayers in a bottom-up approach is reported for polymers, particles, nanoparticles, and carbon nanotubes. Effects of polyelectrolyte multilayers on evaporative self-assembly of particles, which are of interest to a number of applications including photonic crystals, films and substrates, are investigated. Polyelectrolyte multilayer coatings bring multifunctionality to spherical particles and planar films. Studying the construction of polyelectrolyte assemblies is convenient in the planar layout: it is reported here for incorporation of gold and magnetic nanoparticles as well as of carbon nanotubes. Gold nanoparticles concentration is controlled within the films. Potential applications of both spherical structures and planar films are highlighted. Full article

(This article belongs to the Special Issue Polyelectrolytes)

▼ Show Figures

Graphical abstract

9 pages, 351 KiB

Open AccessArticle

Glucan Particle Encapsulated Rifampicin for Targeted Delivery to Macrophages

by Ernesto Soto¹, Yun Seong Kim^2,3, Jinhee Lee², Hardy Kornfeld² and Gary Ostroff^1,*

¹ Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01604, USA

² Department of Medicine, University of Massachusetts Medical School, Worcester, MA 01604, USA

³ Department of Internal Medicine, Pusan National University School of Medicine, Korea

Polymers 2010, 2(4), 681-689; https://doi.org/10.3390/polym2040681 - 6 Dec 2010

Cited by 71 | Viewed by 11358

Abstract

Glucan particles (GPs) are 2–4 mm spherical, hollow, porous shells extracted from Baker’s yeast, Saccharomyces cerevisae. The surface of the GPs is composed primarily of 1,3-b-glucan and the particles are efficiently phagocytosed via receptor-mediated cell uptake by macrophages, phagocytic cells expressing glucan receptors. [...] Read more.

Glucan particles (GPs) are 2–4 mm spherical, hollow, porous shells extracted from Baker’s yeast, Saccharomyces cerevisae. The surface of the GPs is composed primarily of 1,3-b-glucan and the particles are efficiently phagocytosed via receptor-mediated cell uptake by macrophages, phagocytic cells expressing glucan receptors. The hollow cavity of the GPs allows for efficient absorption and encapsulation of payload molecules. Rifampicin (Rif), a drug used in tuberculosis treatment, was encapsulated by precipitation in GPs and trapped using a calcium alginate or chitosan hydrogel to seal the pores of GPs and slow Rif release. Unplugged GP formulations immediately released Rif following particle resuspension in aqueous buffer. Alginate and chitosan sealing of GPs loaded with Rif was able to extend drug release for 24–72 h. GP-Rif formulations containing 10% w/w Rif/GP plugged with a calcium alginate hydrogel were effective at reducing colony forming units of M. tuberculosis strain mc²6020 in infected bone marrow macrophages ~80–90% at 24 and 72 hours. The amount of Rif delivered in the GP formulations was below the free Rif minimal inhibitory concentration demonstrating that GP targeted Rif delivery to macrophages enhances Rif antimicrobial effects. Full article

(This article belongs to the Special Issue Polyelectrolytes)

▼ Show Figures

Figure 1

17 pages, 561 KiB

Open AccessArticle

Tailoring Mechanical Properties of Collagen-Based Scaffolds for Vascular Tissue Engineering: The Effects of pH, Temperature and Ionic Strength on Gelation

by Matteo Achilli and Diego Mantovani^*

Laboratory for Biomaterials and Bioengineering, Department of Materials Engineering & Research Centre, Quebec University Hospital, Laval University, Pavillon Pouliot, 1745-E, Quebec City, G1K 7P4, Canada

Polymers 2010, 2(4), 664-680; https://doi.org/10.3390/polym2040664 - 6 Dec 2010

Cited by 189 | Viewed by 22689

Abstract

Collagen gels have been widely studied for applications in tissue engineering because of their biological implications. Considering their use as scaffolds for vascular tissue engineering, the main limitation has always been related to their low mechanical properties. During the process of in vitro [...] Read more.

Collagen gels have been widely studied for applications in tissue engineering because of their biological implications. Considering their use as scaffolds for vascular tissue engineering, the main limitation has always been related to their low mechanical properties. During the process of in vitro self-assembly, which leads to collagen gelation, the size of the fibrils, their chemical interactions, as well as the resulting microstructure are regulated by three main experimental conditions: pH, ionic strength and temperature. In this work, these three parameters were modulated in order to increase the mechanical properties of collagen gels. The effects on the gelation process were assessed by turbidimetric and scanning electron microscopy analyses. Turbidity measurements showed that gelation was affected by all three factors and scanning electron images confirmed that major changes occurred at the microstructural level. Mechanical tests showed that the compressive and tensile moduli increased by four- and three-fold, respectively, compared to the control. Finally, viability tests confirmed that these gels are suitable as scaffolds for cellular adhesion and proliferation. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Graphical abstract

15 pages, 878 KiB

Open AccessArticle

Surface Roughening of Polystyrene and Poly(methyl methacrylate) in Ar/O₂ Plasma Etching

by Yuk-Hong Ting¹, Chi-Chun Liu², Sang-Min Park², Hongquan Jiang³, Paul F. Nealey² and Amy E. Wendt^1,*

¹ Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

² Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

³ Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA

Polymers 2010, 2(4), 649-663; https://doi.org/10.3390/polym2040649 - 2 Dec 2010

Cited by 76 | Viewed by 17032

Abstract

Selectively plasma-etched polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma [...] Read more.

Selectively plasma-etched polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma etching of PS and PMMA. Variables include ion bombardment energy, polymer molecular weight and etch gas mixture. Roughness data support a proposed model in which surface roughness is attributed to polymer aggregation associated with cross-linking induced by energetic ion bombardment. In this model, RMS roughness peaks when cross-linking rates are comparable to chain scissioning rates, and drop to negligible levels for either very low or very high rates of cross-linking. Aggregation is minimal for very low rates of cross-linking, while very high rates produce a continuous cross-linked surface layer with low roughness. Molecular weight shows a negligible effect on roughness, while the introduction of H and F atoms suppresses roughness, apparently by terminating dangling bonds. For PS etched in Ar/O₂ plasmas, roughness decreases with increasing ion energy are tentatively attributed to the formation of a continuous cross-linked layer, while roughness increases with ion energy for PMMA are attributed to increases in cross-linking from negligible to moderate levels. Full article

(This article belongs to the Special Issue Nano-Structures of Block Copolymers)

▼ Show Figures

Graphical abstract

26 pages, 448 KiB

Open AccessReview

Photo-Induced Micellization of Block Copolymers

by Eri Yoshida^1,* and Satoshi Kuwayama²

¹ Department of Environmental and Life Sciences, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan

² Department of Materials Science, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan

Polymers 2010, 2(4), 623-648; https://doi.org/10.3390/polym2040623 - 26 Nov 2010

Cited by 3 | Viewed by 8387

Abstract

We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light [...] Read more.

We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in this solvent due to irradiation with a high-pressure mercury lamp in the presence of photo-acid generators, such as bis(alkylphenyl)iodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and triphenylsulfonium triflate. The ¹H NMR analysis confirmed that PBSt-b-PSt was converted into poly(4-vinylphenol)-block-PSt by the irradiation, resulting in self-assembly into micelles. The irradiation in the presence of the photo-acid generator also induced the micellization of poly(4-pyridinemethoxymethylstyrene)-block-polystyrene diblock copolymer (PPySt-b-PSt). Micellization occurred by electron transfer from the pyridine to the photo-acid generator in their excited states and provided monodispersed spherical micelles with cores of PPySt blocks. Further, the photo-Claisen rearrangement caused the micellization of poly(4-allyloxystyrene)-block-polystyrene diblock copolymer (PASt-b-PSt). Micellization was promoted in cyclohexane at room temperature without a catalyst. During micellization, the elimination of the allyl groups competitively occurred along with the photorearrangement of the 4-allyloxystyrene units into the 3-allyl-4-hydroxystyrene units. Full article

(This article belongs to the Special Issue Advanced Polymer Architectures)

▼ Show Figures

Figure 1

27 pages, 1719 KiB

Open AccessReview

Phase-Segregated Dendrigraft Copolymer Architectures

by Lorena-Eugenia Sanchez Cadena¹ and Mario Gauthier^2,*

¹ DICIVA, Department of Environmental Sciences, University of Guanajuato/Ex-Hda. El Copal, Km. 9, Carretera Irapuato-Silao, Mexico

² Department of Chemistry, University of Waterloo, 200 University Ave. West, Waterloo, Ontario N2L 3G1, Canada

Polymers 2010, 2(4), 596-622; https://doi.org/10.3390/polym2040596 - 25 Nov 2010

Cited by 8 | Viewed by 9966

Abstract

Dendrigraft polymers have a multi-level branched architecture resulting from the covalent assembly of macromolecular building blocks. Most of these materials are obtained in divergent (core-first) synthetic procedures whereby the molecule grows outwards in successive grafting reactions or generations. Two main types of dendrigraft [...] Read more.

Dendrigraft polymers have a multi-level branched architecture resulting from the covalent assembly of macromolecular building blocks. Most of these materials are obtained in divergent (core-first) synthetic procedures whereby the molecule grows outwards in successive grafting reactions or generations. Two main types of dendrigraft polymers can be identified depending on the distribution of reactive sites over the grafting substrate: Arborescent polymers have a large and variable number of more or less uniformly distributed sites, while dendrimer-like star polymers have a lower but well-defined number of grafting sites strictly located at the ends of the substrate chains. An overview of the synthesis and the characterization of dendrigraft copolymers with phase-segregated morphologies is provided in this review for both dendrigraft polymer families. The tethering of side-chains with a different composition onto branched substrates confers unusual physical properties to these copolymers, which are highlighted through selected examples. Full article

(This article belongs to the Special Issue Nano-Structures of Block Copolymers)

▼ Show Figures

Graphical abstract

21 pages, 282 KiB

Open AccessReview

Tri-n-Butylborane/WaterComplex-Mediated Copolymerization of Methyl Methacrylate with Proteinaceous Materials and Proteins: A Review

by Seiichiro Fujisawa^1,* and Yoshinori Kadoma²

¹ Meikai University School of Dentistry, Sakado, Saitama 350-0283, Japan

² Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Kanda-surugadai, Chiyoda-ku, Tokyo 101-0062, Japan

Polymers 2010, 2(4), 575-595; https://doi.org/10.3390/polym2040575 - 15 Nov 2010

Cited by 14 | Viewed by 9371

Abstract

Previous studies of tri-n-butylborane–initiated graft copolymerization of methyl methacrylates with hydrated proteinous materials and proteins have focused on the number of grafted-poly (MMA) branches as well as the percent graft and graft efficiency. The number of branches in silk fibroin is [...] Read more.

Previous studies of tri-n-butylborane–initiated graft copolymerization of methyl methacrylates with hydrated proteinous materials and proteins have focused on the number of grafted-poly (MMA) branches as well as the percent graft and graft efficiency. The number of branches in silk fibroin is 1.3, whereas the number in collagen, gelatin, ovalbumin and wool are 0.1, 0.04, 0.02 and 0.03, respectively. The number of grafted-PMMA branches in synthetic poly-L-peptides is approximately 10-fold less than that in gelatin, and decline, in the order poly-Ala > poly-Ser > poly-Pro > poly-Glu > poly-Lys. By contrast, poly-Gly, poly-Tyr and poly-Leu have no branches. The co-catalytic effect (the ratio of the number of polymer formed relative to that of control) of amino acids on tri-n-butylborane-initiated polymerization of MMA in the presence of water has been linearly correlated with their ionization potential (IP_koopman); |Äå HOMO (Highest Occupied Molecular Orbital)| (r²= 0.6, outliers: Cys and His); Äå HOMO = [åHOMO_aqua − åHOMO_vacuum] calculated using the semiempirical AM1 method. Also, a significant exponential relationship between the number of branches of poly-L-polypeptides and the Äå HOMO of the corresponding amino acids has been observed (r²= 0.9). A possible grafting site of protein (polypeptide) is discussed. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Figure 1

21 pages, 854 KiB

Open AccessArticle

Functionalization, Compatibilization and Properties of Polyolefin Composites with Natural Fibers

by Mariano Pracella^1,*, Md. Minhaz-Ul Haque² and Vera Alvarez³

¹ Institute of Composite and Biomedical Materials, IMCB- CNR, Via Diotisalvi 2, Pisa 56122, Italy

² Department of Chemical Engineering, Industrial Chemistry and Materials Science, University of Pisa, Pisa 56122, Italy

³ Polymer Division, INTEMA-CONICET, University of Mar del Plata, Mar del Plata, Argentina

Polymers 2010, 2(4), 554-574; https://doi.org/10.3390/polym2040554 - 15 Nov 2010

Cited by 129 | Viewed by 19705

Abstract

The article is focused on analyzing the effect of functionalization and reactive processing on the morphological, thermal, rheological and mechanical properties of composites of isotactic polypropylene (PP), polystyrene (PS), poly(ethylene-vinyl acetate) (EVA), with cellulose fibers, hemp or oat as natural fillers. Both polymers [...] Read more.

The article is focused on analyzing the effect of functionalization and reactive processing on the morphological, thermal, rheological and mechanical properties of composites of isotactic polypropylene (PP), polystyrene (PS), poly(ethylene-vinyl acetate) (EVA), with cellulose fibers, hemp or oat as natural fillers. Both polymers and fibers were modified with bi-functional monomers (glycidyl methacrylate, GMA; maleic anhydride, MA) capable of facilitating chemical reactions between the components during melt mixing. Polyolefin copolymers containing reactive groups (PP-g-GMA, SEBS-g-MA, PS-co-MA, etc.) were used as compatibilizers. Optical and SEM microscopy, FTIR, RX, DSC, TGA, DMTA, rheological and mechanical tests were employed for the composites characterization. The properties of binary and ternary systems have been analyzed as a function of both fiber and compatibilizer content. All compatibilized systems showed enhanced fiber dispersion and interfacial adhesion. The phase behavior and the thermal stability of the composites were affected by the chemical modification of the fibers. Marked changes in the overall crystallization processes and crystal morphology of PP composites were observed owing to the nucleating effect of the fibers. The tensile mechanical behavior of the compatibilized composites generally resulted in a higher stiffness, depending on the fiber amount and the structure and concentration of compatibilizer. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Figure 1

32 pages, 1102 KiB

Open AccessReview

The Use of Natural Polymers in Tissue Engineering: A Focus on Electrospun Extracellular Matrix Analogues

by Scott A. Sell^1,2, Patricia S. Wolfe¹, Koyal Garg¹, Jennifer M. McCool¹, Isaac A. Rodriguez¹ and Gary L. Bowlin^1,*

¹ Department of Biomedical Engineering, Virginia Commonwealth University, 401 W. Main St, Richmond, VA 23284, USA

² Physical Medicine & Rehabilitation Service, Hunter Holmes McGuire VA Medical Center, 1201 Broad Rock Blvd., Richmond, VA 23249, USA

Polymers 2010, 2(4), 522-553; https://doi.org/10.3390/polym2040522 - 9 Nov 2010

Cited by 509 | Viewed by 37462

Abstract

Natural polymers such as collagens, elastin, and fibrinogen make up much of the body’s native extracellular matrix (ECM). This ECM provides structure and mechanical integrity to tissues, as well as communicating with the cellular components it supports to help facilitate and regulate daily [...] Read more.

Natural polymers such as collagens, elastin, and fibrinogen make up much of the body’s native extracellular matrix (ECM). This ECM provides structure and mechanical integrity to tissues, as well as communicating with the cellular components it supports to help facilitate and regulate daily cellular processes and wound healing. An ideal tissue engineering scaffold would not only replicate the structure of this ECM, but would also replicate the many functions that the ECM performs. In the past decade, the process of electrospinning has proven effective in creating non-woven ECM analogue scaffolds of micro to nanoscale diameter fibers from an array of synthetic and natural polymers. The ability of this fabrication technique to utilize the aforementioned natural polymers to create tissue engineering scaffolds has yielded promising results, both in vitro and in vivo, due in part to the enhanced bioactivity afforded by materials normally found within the human body. This review will present the process of electrospinning and describe the use of natural polymers in the creation of bioactive ECM analogues in tissue engineering. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Graphical abstract

17 pages, 401 KiB

Open AccessArticle

Periodate Oxidation of Methylcellulose: Characterization and Properties of Oxidized Derivatives

by Marguerite Rinaudo

Centre de Recherches sur les Macromolecules Végétales (CERMAV-CNRS) affiliated with Joseph Fourier University, BP53, 38041 Grenoble Cedex 9, France

Polymers 2010, 2(4), 505-521; https://doi.org/10.3390/polym2040505 - 29 Oct 2010

Cited by 35 | Viewed by 12757

Abstract

In this paper, the behavior of oxidized methylcelluloses is compared with that of the initial methylcellulose, an amphiphilic cellulose derivative. Methylcelluloses are important for many applications in the cosmetic and food industries. The mechanism of thermo-gelation of methylcellulose is briefly explained as well [...] Read more.

In this paper, the behavior of oxidized methylcelluloses is compared with that of the initial methylcellulose, an amphiphilic cellulose derivative. Methylcelluloses are important for many applications in the cosmetic and food industries. The mechanism of thermo-gelation of methylcellulose is briefly explained as well as the method of oxidation of polysaccharides. Then, our experiments involve the preparation of oxidized methylcelluloses: three degrees of oxidation are prepared and the new polymers are characterized by NMR, IR, SEC and rheology. Oxidation with periodate theoretically allows introduction of two aldehydic groups on C2–C3 glycol positions of anhydroglucose units. This reaction not only enhances the flexibility of the cellulosic backbone, but also causes a decrease in the molecular weight. In particular, the rheological behavior of methylcellulose and oxidized methylcellulose as a function of temperature is examined. The oxidized methylcelluloses prepared, being rich in aldehyde functions, become interesting intermediaries to prepare new cellulose derivatives. In this paper, three examples of reductive amination based on the reaction of modified methylcelluloses and −NH₂ groups of different molecules are described: β-alanine produces a polyelectrolyte; chitosan and hyaluronan-ADH (derivative obtained with adipic dihydrazide allowing introduction of −NH₂functions on HA backbone) are crosslinked and give new biocompatible hydrogels. Full article

(This article belongs to the Collection Polysaccharides)

▼ Show Figures

Graphical abstract

15 pages, 1786 KiB

Open AccessArticle

Enhanced Photophysical Properties of Nanopatterned Titania Nanodots/Nanowires upon Hybridization with Silica via Block Copolymer Templated Sol-Gel Process

by Dinakaran Kannaiyan^1,†, Saji Thomas Kochuveedu^1,†, Yoon Hee Jang¹, Yu Jin Jang¹, Ji Yong Lee¹, Jieun Lee¹, Juyon Lee¹, Jooyong Kim² and Dong Ha Kim^1,*

¹ Department of Chemistry and Nano Science, Division of Molecular and Life Sciences, College of Natural Sciences, Ewha Womans University, 11-1 Daehyun-dong, Seodaemun-gu, Seoul 120-750, Korea

² Department of Organic Materials and Fiber Engineering, Soongsil University, 511 Sangdo-Dong, Dongjak-Gu, Seoul 156-743, Korea

^† The authors contributed equally to this work.

Polymers 2010, 2(4), 490-504; https://doi.org/10.3390/polym2040490 - 25 Oct 2010

Cited by 46 | Viewed by 14201

Abstract

We fabricated titanium dioxide (TiO₂)-silica (SiO₂) nanocomposite structures with controlled morphology by a simple synthetic approach using cooperative sol-gel chemistry and block copolymer (BCP) self-assembly. Mixed TiO₂-SiO₂ sol-gel precursors were blended with amphiphilic poly(styrene-block-ethylene oxide) (PS- [...] Read more.

We fabricated titanium dioxide (TiO₂)-silica (SiO₂) nanocomposite structures with controlled morphology by a simple synthetic approach using cooperative sol-gel chemistry and block copolymer (BCP) self-assembly. Mixed TiO₂-SiO₂ sol-gel precursors were blended with amphiphilic poly(styrene-block-ethylene oxide) (PS-b-PEO) BCPs where the precursors were selectively incorporated into the hydrophilic PEO domains. Changing the volumetric ratio of TiO₂-SiO₂ sol-gel precursor from 5% to 20%, a stepwise structural inversion occurred from nanodot arrays to discrete nanowires. Template free hybrid inorganic nanostructures were produced after the removal of PS-b-PEO by irradiation of UV light. The morphological evolution and photophysical properties were investigated by microscopic studies, UV-visible absorption and photocatalytic properties. Full article

(This article belongs to the Special Issue Nano-Structures of Block Copolymers)

▼ Show Figures

Graphical abstract

20 pages, 880 KiB

Open AccessReview

Block Copolymer Nanostructures for Technology

by Yu-Chih Tseng^* and Seth B. Darling

Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA

Polymers 2010, 2(4), 470-489; https://doi.org/10.3390/polym2040470 - 20 Oct 2010

Cited by 136 | Viewed by 24411

Abstract

Nanostructures generated from block copolymer self-assembly enable a variety of potential technological applications. In this article we review recent work and the current status of two major emerging applications of block copolymer (BCP) nanostructures: lithography for microelectronics and photovoltaics. We review the progress [...] Read more.

Nanostructures generated from block copolymer self-assembly enable a variety of potential technological applications. In this article we review recent work and the current status of two major emerging applications of block copolymer (BCP) nanostructures: lithography for microelectronics and photovoltaics. We review the progress in BCP lithography in relation to the requirements of the semiconductor technology roadmap. For photovoltaic applications, we review the current status of the quest to generate ideal nanostructures using BCPs and directions for future research. Full article

(This article belongs to the Special Issue Nano-Structures of Block Copolymers)

▼ Show Figures

Figure 1

16 pages, 1197 KiB

Open AccessReview

Design and Application of Nanoscale Actuators Using Block-Copolymers

by Joshua M. G. Swann¹ and Paul D. Topham^2,*

¹ Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK

² Chemical Engineering and Applied Chemistry, Aston University, Birmingham, B4 7ET, UK

Polymers 2010, 2(4), 454-469; https://doi.org/10.3390/polym2040454 - 15 Oct 2010

Cited by 20 | Viewed by 15477

Abstract

Block copolymers are versatile designer macromolecules where a “bottom-up” approach can be used to create tailored materials with unique properties. These simple building blocks allow us to create actuators that convert energy from a variety of sources (such as chemical, electrical [...] Read more.

Block copolymers are versatile designer macromolecules where a “bottom-up” approach can be used to create tailored materials with unique properties. These simple building blocks allow us to create actuators that convert energy from a variety of sources (such as chemical, electrical and heat) into mechanical energy. In this review we will discuss the advantages and potential pitfalls of using block copolymers to create actuators, putting emphasis on the ways in which these materials can be synthesised and processed. Particular attention will be given to the theoretical background of microphase separation and how the phase diagram can be used during the design process of actuators. Different types of actuation will be discussed throughout. Full article

(This article belongs to the Special Issue Nano-Structures of Block Copolymers)

▼ Show Figures

Graphical abstract

14 pages, 428 KiB

Open AccessReview

Oleic and Undecylenic Acids as Renewable Feedstocks in the Synthesis of Polyols and Polyurethanes

by Gerard Lligadas, Juan C. Ronda, Marina Galià and Virginia Cádiz^*

Departament de Química Analítica i Química Orgànica, Universitat Rovira i Virgili, C/Marcel.lí Domingo s/n, 43007 Tarragona, Spain

Polymers 2010, 2(4), 440-453; https://doi.org/10.3390/polym2040440 - 14 Oct 2010

Cited by 95 | Viewed by 14533

Abstract

Nowadays, the utilization of raw materials derived from renewable feedstock is in the spotlight of the chemical industry, as vegetable oils are one of the most important platform chemicals due to their universal availability, inherent biodegradability and low price. Taking into account that [...] Read more.

Nowadays, the utilization of raw materials derived from renewable feedstock is in the spotlight of the chemical industry, as vegetable oils are one of the most important platform chemicals due to their universal availability, inherent biodegradability and low price. Taking into account that polyurethanes are one of the most important industrial products exhibiting versatile properties suitable for use in many fields, our research is focused on exploiting fatty acids in the preparation of biobased polyols and polyurethanes. This review is organized as a function of the nature of the final polyurethane systems; hence we describe the preparation of linear thermoplastic and crosslinked polyurethanes derived from oleic and undecylenic acids-based diols and polyols, respectively. Full article

(This article belongs to the Special Issue Natural Polymers)

▼ Show Figures

Graphical abstract

22 pages, 809 KiB

Open AccessArticle

New Biocompatible Polyesters Derived from α-Amino Acids: Hydrolytic Degradation Behavior

by Naomi Cohen-Arazi^*, Abraham J. Domb and Jeoshua Katzhendler

Institute of Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Israel

Polymers 2010, 2(4), 418-439; https://doi.org/10.3390/polym2040418 - 13 Oct 2010

Cited by 22 | Viewed by 11295

Abstract

New polymers were synthesized from α-hydroxy acids derived from the natural amino acids Ile, Leu, Phe, and Val, combined with lactic acid, glycolic acid and 6-hydroxyhexanoic acid by direct condensation. The toxicity was determined and the degradation process of these polyesters was investigated [...] Read more.

New polymers were synthesized from α-hydroxy acids derived from the natural amino acids Ile, Leu, Phe, and Val, combined with lactic acid, glycolic acid and 6-hydroxyhexanoic acid by direct condensation. The toxicity was determined and the degradation process of these polyesters was investigated under physiological conditions by analyzing the composition of the degraded polymers and the oligomers cleaved in the buffer medium. The polymers were found to be non toxic to two cell lines. Polymers displayed a biphasic degradation behavior. In most cases, a linear relationship was found between the weight loss constant and the hydrophobicity of the polymers, Log P. Regarding the second stage of weight loss, it is apparent that polymers derived from α-hydroxy(L)isoleucine ((L)HOIle) and α-hydroxy(L)Valine ((L)HOVal) degraded much faster than those derived from α-hydroxy(L)leucine ((L)HOLeu) and α-hydroxy(L)phenylalanine ((L)HOPhe), probably due to different spatial orientation of the side chains. Copolymers of 6-hydroxyhexanoic acid displayed slow degradation rates as expected, whereas the degradation profile of copolymers of lactic acid was similar to the other homopolymers. These new polyesters may serve as potential biocompatible materials for medical applications. Full article

(This article belongs to the Special Issue Advanced Polymer Architectures)

▼ Show Figures

Graphical abstract

11 pages, 429 KiB

Open AccessArticle

Synthesis of Propargyl-Terminated Heterobifunctional Poly(ethylene glycol)

by Changhai Lu¹ and Wen Zhong^1,2,*

¹ Department of Textile Sciences, Faculty of Human Ecology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

² Department of Medical Microbiology, Faculty of Medicine, University of Manitoba, Winnipeg, MB R3T 2N2, Canada

Polymers 2010, 2(4), 407-417; https://doi.org/10.3390/polym2040407 - 13 Oct 2010

Cited by 17 | Viewed by 15433

Abstract

Novel propargyl-ended heterobifunctional poly(ethylene glycol) (PEG) derivatives with hydroxyl, carboxyl, mercapto or hydrazide end groups were synthesized with simplicity yet high efficiency. PEG (M_w = 3500 Da) with an α-hydroxyl group and an ω-carboxyl was used as the starting polymer. The [...] Read more.

Novel propargyl-ended heterobifunctional poly(ethylene glycol) (PEG) derivatives with hydroxyl, carboxyl, mercapto or hydrazide end groups were synthesized with simplicity yet high efficiency. PEG (M_w = 3500 Da) with an α-hydroxyl group and an ω-carboxyl was used as the starting polymer. The carboxyl group of the bifunctional PEG was modified into a propargyl, then carboxyl, mercapto or hydrazide groups were introduced to the other end of the bifunctional PEG by modifying the bifunctional PEG’s hydroxyl group with succinic anhydride, cysteamide or tert-butyl carbazate, respectively. This method can be useful to the development of PEG-based bioconjugates for a variety of biomedical applications. Full article

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

▼ Show Figures

Figure 1

14 pages, 880 KiB

Open AccessArticle

Polymerization in Liquid Crystal Medium: Preparation of Polythiophene Derivatives Bearing a Bulky Pyrimidine Substituent

by Satoshi Ohkawa, Reina Ohta, Kohsuke Kawabata and Hiromasa Goto^*

Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan

Polymers 2010, 2(4), 393-406; https://doi.org/10.3390/polym2040393 - 11 Oct 2010

Cited by 10 | Viewed by 9059

Abstract

We carried out polycondensation of monomers bearing a bulky pyrimidine substituent in a liquid crystal solvent. The resultant polymers formed nematic liquid crystals. The polymers prepared in liquid crystals had higher coplanarity than the polymers prepared in toluene. This can be due to [...] Read more.

We carried out polycondensation of monomers bearing a bulky pyrimidine substituent in a liquid crystal solvent. The resultant polymers formed nematic liquid crystals. The polymers prepared in liquid crystals had higher coplanarity than the polymers prepared in toluene. This can be due to the fact that the ordered medium of the liquid crystal produces an aggregated structure with well-developed π-stacking between the main chains. The present results demonstrated that polymerization of bulky monomers is possible in liquid crystal solvents. Full article

▼ Show Figures

Figure 1

15 pages, 223 KiB

Open AccessArticle

Fine-Tuning of Polymeric Resins and their Interfaces with Amorphous Calcium Phosphate. A Strategy for Designing Effective Remineralizing Dental Composites

by Joseph M. Antonucci¹ and Drago Skrtic^2,*

¹ Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA

² Paffenbarger Research Center, American Dental Association Foundation, Gaithersburg, MD 20899, USA

^† Official contribution of NIST; not subject to copyrights in USA.

Polymers 2010, 2(4), 378-392; https://doi.org/10.3390/polym2040378 - 29 Sep 2010

Cited by 12 | Viewed by 8558

Abstract

For over a decade our group has been designing, preparing and evaluating bioactive, remineralizing composites based on amorphous calcium phosphate (ACP) fillers embedded in polymerized methacrylate resin matrices. In these studies a major focus has been on exploring structure-property relationships of the matrix [...] Read more.

For over a decade our group has been designing, preparing and evaluating bioactive, remineralizing composites based on amorphous calcium phosphate (ACP) fillers embedded in polymerized methacrylate resin matrices. In these studies a major focus has been on exploring structure-property relationships of the matrix phase of these composites on their anti-cariogenic potential. The main challenges were to gain a better understanding of polymer matrix/filler interfacial properties through controlling the surface properties of the fillers or through fine-tuning of the resin matrix. In this work, we describe the effect of chemical structure and composition of the resin matrices on some of the critical physicochemical properties of the copolymers and their ACP composites. Such structure-property studies are essential in formulating clinically effective products, and this knowledge base is likely to have strong impact on the future design of therapeutic materials, appropriate for mineral restoration in defective tooth structures. Full article

▼ Show Figures

Figure 1

14 pages, 1000 KiB

Open AccessArticle

Chemically Induced Dynamic Nuclear Polarization during the Thermolysis of Alkoxyamines: A New Approach to Detect the Occurrence of H-Transfer Reactions

by Maria Edeleva^1,2, Sylvain R. A. Marque^3,*, Denis Bertin³, Didier Gigmes³, Yohann Guillaneuf³ and Elena Bagryanskaya^2,*

¹ Physical Chemistry Department, Novosibirsk State University, Novosibirsk, Russia

² International Tomography Center SB RAS, Novosibirsk, Russia

³ UMR 6264-LCP, CNRS-Aix-Marseille Université, , case 521, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France

Polymers 2010, 2(4), 364-377; https://doi.org/10.3390/polym2040364 - 28 Sep 2010

Cited by 9 | Viewed by 9552

Abstract

Thermal decomposition of alkoxyamines in the presence of scavengers was found to proceed with the formation of chemically induced nuclear polarization detected by 1H NMR. The distinctive Chemically Induced Dynamic Nuclear Polarization (CIDNP) features were studied using the example of three alkoxyamines: 4-nitrophenyl [...] Read more.

Thermal decomposition of alkoxyamines in the presence of scavengers was found to proceed with the formation of chemically induced nuclear polarization detected by 1H NMR. The distinctive Chemically Induced Dynamic Nuclear Polarization (CIDNP) features were studied using the example of three alkoxyamines: 4-nitrophenyl 2-(2,2,6,6-tetramethylpiperidin-1-yloxy)-2-methylpropanoate (1a), 4-nitrophenyl 2-(2,2-diphenyl-3-phenylimino-2,3-dihydroindol-1-yloxy)-2-methylpropanoate (2a) and 4-nitrophenyl 2-(2,2,5,5-tetramethyl-4-phenyl-2H-imidazol-1-oxy)-2-methylpropanoate (3a) in the presence of PhSH. The analysis of CIDNP signs of methacrylate protons allows us to conclude on the occurrence of hydrogen atom transfer reaction in geminate radical pair formed in alkoxyamine thermolysis. Thus, CIDNP is a fast and sensitive method to detect the occurrence of intra/intermolecular hydrogen transfer in alkoxyamine thermolysis. Full article

(This article belongs to the Special Issue Advanced Polymer Architectures)

▼ Show Figures

Graphical abstract

Journal Menu

Journal Browser

Polymers, Volume 2, Issue 4 (December 2010) – 24 articles , Pages 364-798

Further Information

Guidelines

MDPI Initiatives

Follow MDPI