bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of chitosan-containing nanofibres by electrospinning of chitosan/poly(ethylene oxide) blend solutions
Authors: Spasova Maria , Manolova Nevena , Paneva Dilyana , Rashkov Iliya 
Published: August 2014

Abstract The first successful preparation of chitosan-containing nanofibres was achieved by electrospinning of chitosan/poly(ethylene oxide) (PEO) blend aqueous solutions. The diameters of the nanofibres were in the range 40 - 290 nm and decreased with increasing chitosan content and decreasing total concentration. An increase of the applied field strength leads to an increase of the diameter of the nanofibres and to a broadening of the size distribution. The possibility to prepare nanofibres containing a model drug - potassium 5-nitro-8-quinolinolate (K5N8Q), a broad-spectrum antimicrobial and antimycotic agent - was shown. The incorporation of K5N8Q in the nanofibres resulted in a decrease of the nanofibre diameters and the appearance of bead-shaped defects. Non-woven mats from the drugloaded nanofibres with composition chitosan : PEO = 1:1 (w/w) and 1% K5N8Q showed antibacterial and antimycotic activity against E. coli, S. aureus and C.albicans.
Molecular deformation mechanisms and mechanical properties of polymers simulated by molecular dynamics
Authors: Simões Ricardo , Cunha António M. , Brostow Witold 
Published: August 2014

Abstract Virtual polymeric materials were created and used in computer simulations to study their behavior under uniaxial loads. Both single-phase materials of amorphous chains and two-phase polymer liquid crystals (PLCs) have been simulated using the molecular dynamics method. This analysis enables a better understanding of the molecular deformation mechanisms in these materials. It was confirmed that chain uncoiling and chain slippage occur concurrently in the materials studied following predominantly a mechanism dependent on the spatial arrangement of the chains (such as their orientation). The presence of entanglements between chains constrains the mechanical response of the material. The presence of a rigid second phase dispersed in the flexible amorphous matrix influences the mechanical behavior and properties. The role of this phase in reinforcement is dependent on its concentration and spatial distribution. However, this is achieved with the cost of increased material brittleness, as crack formation and propagation is favored. Results of our simulations are visualized in five animations.
Molecular and supramolecular approaches for tuning properties of new polyketanils
Authors: Sęk Danuta , Iwan Agnieszka 
Published: August 2014

Abstract A new family of π-conjugated polyketanils was synthesized and thermal and optical properties of the polymers were tuned by ‘chain engineering’, consisting of the appropriate design of chain building blocks using diamines and diketones with various chemical structures, and ‘dopant engineering’ in which a specially designed multifunctional dopant was used, 1,2-(di-2-ethylhexyl) ester of 4-sulfophthalic acid, capable of specific interaction with the host polymer. The structure of the dopant creates a new type of supramolecular comb-shaped architecture in which the lateral groups, anions of the sulfophthalic acid residue, are ionically bonded to the main chain via protonation of ketimine nitrogen atoms. This specific interaction of the dopant with the host polymer influences the polyketanils’ properties and the following changes were observed: decreasing glass transition temperature and improvement of polymer film flexibility, as well as a bathochromic shift of the photoluminescence emission band.
Relationship between structural evolution and rheological measurements for polymer + organoclay nanocomposites
Authors: Kim Hee Bong , Hyun Yang Hoon , Lim Sung Taek , Choi Hyoung Jin , Jhon Myung S. 
Published: August 2014

AbstractNanocomposites with synthetic biodegradable aliphatic polyesters (BAP) were synthesized by the solution intercalation method with addition of organically modified montmorillonite. The hybrid structural evolution, caused by nanoscopic interaction between matrix polymer and layered silicate, was analyzed using viscoelastic properties obtained from oscillatory rheological measurements. Changes of viscoelastic properties to more solid-like, especially in the terminal region, were explained by both formation of specific BAP chain mesostructures with organoclay incorporated and a rheological percolation threshold. This behaviour was analyzed via a modified Cole-Cole plot evaluating the structural changes with filler concentration as well as the frequency dependence of dynamic modulus, complex modulus, and phase angle. Furthermore, the stress relaxation behaviour successfully demonstrated structural changes and critical concentration of nanocomposites with a jump shift of the longest relaxation time towards longer time.
Wetting of bioactive glass surfaces by poly(α-hydroxyacid) melts: interaction between Bioglass® and biodegradable polymers
Authors: Blaker Jonny J. , Maquet Véronique , Boccaccini Aldo R. , Jérôme Robert , Bismarck Alexander 
Published: August 2014

AbstractThe interfacial characteristics between bioactive glass (45S5 Bioglass®) surfaces and poly(α-hydroxyacid) melts have been assessed by direct wetting measurements. In particular, the wettability of Bioglass® powder by poly(D,Llactide) (PDLLA) and poly(D,L-lactide-co-glycolide) (PLGA) was assessed by imbibition measurements. Additionally, the equilibrium contact angles of PDLLA and PLGA melts on a sintered Bioglass® surface were measured. The surface energy of the bioactive glass and the polymers was determined from contact angles measured using various test liquids on PDLLA, PLGA and Bioglass® solid substrates. There are sufficient adhesive interactions between the polymers and Bioglass®. A simple heat treatment of the bioactive glass in an inert gas atmosphere leads to an improved wetting behaviour, indicating increased adhesive interactions. Scanning electron micrographs of the polymer + Bioglass® composites formed by polymer penetration into the powder bed show the formation of a ‘good quality’ interface.
Modification of polymers by ultrasound treatment in aqueous solution
Authors: Rokita Bozena , Czechowska-Biskup Renata , Ulanski Piotr , Rosiak Janusz M. 
Published: August 2014

AbstractUltrasound treatment, as an alternative to chemical and radiation-based processes, is an interesting technique for the modification of average molecular weights of natural and synthetic polymers in aqueous solution. Degradation is the observed main effect for strongly hydrophilic compounds - poly(acrylic acid) and chitosan. It is demonstrated that this process is caused by OH radicals as well as mechanochemical effects. Studies on more hydrophobic polymers - poly(ethylene oxide) and poly(ethylene glycol)s - indicate that here cross-linking and degradation occur side-by-side. The net effect of these competing reactions depends on the length of the polymer chains.
Potentials of solvation of macromolecules as a measure of intermolecular interactions under viscous flow conditions
Authors: Filimoshkin Anatoliy , Safronov Sergey , Safronova Marina , Chernov Eugene 
Published: August 2014

AbstractViscous flow of polymer solutions is depicted as a combined totality of elementary acts of flow within the bounds of the thermodynamic Joule cycle. Intrinsic viscosity of polymer solutions is represented as an energetical function of intermolecular interactions rather than a measure of additional loss of energy due to the rotational and viscoelastic deformations of macromolecules in the flow. A new theoretical concept in the light of the thermodynamic cycle analogous to that of Joule is brought forward to describe the viscous flow of polymer solutions. The concept is represented as a sequence of elementary cyclic processes described by equations, which establish a relationship between solvation potentials (E) and thermodynamic parameters such as temperature and volume. Solvation potentials are identified with the value of maximal solvation work and allow evaluating the energy of the corresponding intermolecular interactions via E, individually of electrostatic (Ea) and covalent (Eb1, Eb2) nature.
Novel, biocompatible polyether(meth)acrylate-based formulations for stereolithography – A new flexible material class for three-dimensional applications
Authors: Bens Arthur Thomas , Tille Carsten , Bermes Günter , Emons Moritz , Seitz Hermann 
Published: August 2014

AbstractHerein we present a novel polyether(meth)acrylate-based resin material for stereolithography and other photolithographic applications with outstanding flexible material characteristics. This group of photopolymeric resin products combines the advantages of a non-toxic (meth)acrylate-based process material with a broad spectrum of adjustable low Young’s modulus material characteristics. In contrast to the mostly rigid and non-flexible process materials used at the moment in the engineering world, these formulations are able to fulfil the extended need for a very flexible and also biocompatible engineering material, especially for threedimensional models or prototypes in the medical technology area. A short overview over the bandwidth of possible material characteristics is given in this publication.
Scanning electron microscopy investigation of tooth/filling bonding
Authors: Siejka-Kulczyk Joanna , Lewandowska Małgorzata , Raczyńska Marta , Jodkowska Elżbieta , Kurzydłowski Krzysztof J. 
Published: August 2014

AbstractScanning electron microscopy (SEM) investigations have been conducted to determine the influence of selected material on tissue/material bonding. Extracted human teeth were used in this study. Several resin composites were tested as dental fillings. To reveal the structure of the tissue/filling interface, the teeth were cut parallel to the long axis. Bonding quality was determined by direct SEM observation and microanalysis with X-ray energy spectrometry (EDX). The investigated materials show good bonding with enamel.
Separation of linear and star-shaped polystyrenes by two-dimensional chromatography
Authors: Gerber Johannes , Radke Wolfgang 
Published: August 2014

AbstractInvestigation of star-shaped polystyrenes using gradient chromatography shows a retention that only depends on the total molecular weight and not on the number or molecular weight of the arms. In contrast, size-exclusion chromatography (SEC) separates according to hydrodynamic volume. For a mixture of a star polymers having an arm molecular weight of 4800 and a linear polystyrene a direct 2-dimensional separation using gradient chromatography as a first dimension and SEC as a second dimension resulted in a clear separation of the different topologies. Star polymers of higher arm molecular weight could not be separated from their linear analogues by direct coupling of gradient chromatography and SEC.
Degradation of polymeric systems aimed at temporary therapeutic applications: Structure-related complications
Authors: Vert Michel 
Published: August 2014

AbstractThe number of degradable or biodegradable polymers that are aimed or claimed as aimed at therapeutic purposes is rapidly increasing in literature. In most cases, contributions deal primarily with synthesis. However it is the matching of degradation characteristics to application requirements that is important. This contribution, based on personal experience, is aimed at discussing some of the structure-related complications that can be expected when a polymeric therapeutic device degrades in an aqueous medium or in an animal organism. It is shown that dramatic changes can be observed because of selective degradation of some parts leading to the formation of undesired degradation by-products or undesired changes of properties.
Thermodynamic and electrochemical study of multicomponent polymer complexes of varying composition
Authors: Sharma nee Chhabra Mamta , Sharma Sandeep 
Published: August 2014

AbstractMulticomponent complexes of varying composition have been prepared from poly(methacrylic acid-co-acrylamide), poly(ethyleneimine) and poly(vinylpyrrolidone). Stability constants and related thermodynamic parameters have been determined. Interpretations have been sought in terms of secondary binding forces and their magnitude.
Carbon-chain polymers ‘grafting from’ inorganic nanoparticles
Authors: Liu Peng 
Published: August 2014

Abstract‘Grafting from’ methods can achieve higher percentages of grafting than ‘grafting to’ methods in the preparation of carbon-chain polymer grafted inorganic nanoparticles (CCP-INs). ‘Grafting from’ methods - such as one-pot method, macro-monomer, macro chain transfer agent, macro-initiator, and macro-iniferter methods, used for the preparation of CCP-INs in our laboratory in the recent years - are reviewed and the grafting parameters are compared. Characterization of the CCP-INs is also described.
Antimicrobial activity of polystyrene particles coated by photo-crosslinked block copolymers containing a biocidal polymethacrylate block
Authors: Lenoir Sandrine , Pagnoulle Christophe , Detrembleur Christophe , Galleni Moreno , Jérôme Robert 
Published: August 2014

AbstractA commercially available poly(ethylene-co-butylene) copolymer, endcapped by a short polyisoprene block and a hydroxyl group (PI-b-PEB-OH), has been derivatized into a macroinitiator for atom transfer radical polymerization (ATRP) by esterification of the hydroxyl end-group by an activated bromidecontaining acyl bromide. Two types of triblock copolymers, PI-b-PEB-b-poly- (dimethylaminoethyl methacrylate) (PDMAEMA) and PI-b-PEB-b-poly[2-(tert-butylamino) ethyl methacrylate] (PTBAEMA), have been synthesized and used to coat polystyrene particles. These coatings have been permanently immobilized by UV cross-linking of the isoprene units. They exhibit a biocidal activity against Gramnegative bacteria either intrinsically in case of the PTBAEMA block or upon quaternization of the PDMAEMA block by octyl bromide. The antimicrobial activity is directly related to the concentration of coated PS particles in the medium.
Kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble fluoro monomer
Authors: Suzuki Kiyoshi , Yamada Yasutaka , Fujita Kazumi , Nomura Mamoru , Saito Hideya 
Published: August 2014

AbstractIn order to clarify the kinetics and mechanism of miniemulsion polymerization of a sparingly water-soluble monomer, the miniemulsion polymerization of 1,1,2,2-tetrahydroperfluorodecyl acrylate was conducted at 50°C using potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier, respectively. It was found that the rate of polymerization was proportional to the 0.65 power of the initial initiator concentration and to the 0.30 power of the number of miniemulsion droplets (latex particles). It is pointed out that the kinetics of this polymerization system may be subject to the modified case III kinetics of emulsion polymerization with predominant bimolecular termination in the aqueous phase.
Monitoring morphology and properties of hybrid organicinorganic materials from in situ polymerization of tetraethoxysilane in polyimide polymer: 1. Effect of the coupling agent on the microstructure and interfacial interaction
Authors: Kaddami Hamid , Becker-Willinger Carsten , Schmid Helmut 
Published: August 2014

AbstractTransmission electron microscopy (TEM), small angle X-ray (SAXS) and dynamical mechanical thermal analysis (DMTA) were used to characterize the morphology and thermo-mechanical properties of hybrid organic inorganic materials. These materials were based on polyimide (PI) and tetraethoxysilane (TEOS). Polyimide polymer is prepared from 4,4’-oxydianiline (ODA) 2,2-Bis(3- amino-4-hydroxyphenyl) hexafluoro-propane (6F-OHDA) pyromellitic dianhydride (PMDA) polyamic polymer. In one family of hybrid materials 3- isocyanatopropyltriethoxysilane (ICTS) is used as coupling agent in order to enhance the interfacial interaction between polyimide and silica. It was possible to modulate the morphology as well as the optical and thermo-mechanical properties of these hybrid materials depending on the formulation used. TEM and SAXS analysis indicated that silica domains on the nanoscale level are obtained when coupling agent is used in the formulation. Additionally the TEM and SAXS analysis indicated that miscibility of the organic and the inorganic phases on the molecular scale is obtained in the hybrid films when ICTS as coupling agent is added to the polyamic acid. These techniques show a fractal structure of the hybrid materials with coupling agent. This was confirmed with DMTA analysis which shows very high temperature relaxation (more than 450°C). From this result it could be derived that the addition of ICTS causes a morphological transformation from discrete particulate microstructure to fine interpenetrated or co-continuous phases. The intimate miscibility of the phases is accompanied at the same time by the amelioration of thermo-mechanical properties of the hybrid films.
Homopolymerization of a highly polar zwitterionic methacrylate in ionic liquids and its copolymerization with a non-polar methacrylate
Authors: Strehmel Veronika , Laschewsky André , Wetzel Hendrik 
Published: August 2014

AbstractFree radical homo- and copolymerization of the highly polar 3-(N-[2- methacryloyloxyethyl]-N,N-dimethylammonio)propane sulfonate with the nonpolar n-butylmethacrylate was investigated in the ionic liquids 1-butyl-3-methyl imidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium hexafluoro phosphate, and compared to analogous polymerizations in standard solvents. Higher molar masses are obtained for the zwitterionic homopolymer when the polymerization is carried out in an ionic liquid compared to the classical reaction in water. Although homopolymerization of the sulfobetain monomer as well as of nbutylmethacrylate results in phase separation during the polymerization process, copolymerization of a stoichiometric ratio of the two monomers in the ionic liquids produced transparent gels indicating that no macrophase separation occurs. The use of ionic liquids as reaction medium improved the copolymerization behavior of the two methacrylates significantly. Whereas only minor amounts of n-butyl methacrylate were incorporated in the copolymer when synthesized in acetonitrile, the content of the non-polar monomer units in the zwitterionic copolymer approached increasingly its content in the polymerization mixture when ionic liquids were employed as solvents.
Activation of organoclays and preparation of polyethylene nanocomposites
Authors: Chaiko David J. 
Published: August 2014

AbstractA dimethyl dihydrogenated tallow ammonium bentonite, edge modified with 1-hydroxydodecane-1,1-diphosphonic acid, was activated by intercalation of polyethylene-block-poly(ethylene glycol). A high-density polyethylene (HDPE) nanocomposite was produced by the gradual dilution of the intercalated organoclay with HDPE, via melt mixing, until a final clay concentration of 0.3 wt% was reached. While polymer crystallinity was unaffected by the addition of the clay, polymer transparency increased dramatically. Microscopic examination of compression molded films verified that polymer nucleation increased to such an extent that the normal spherulitic structure was completely absent. A significant reduction in gas transmission accompanied the increased film clarity. Compared to the pure polymer, oxygen and water vapor permeabilities were reduced by approximately 55 and 70%, respectively. With proper dispersion, significant improvements in both physical and barrier properties are achievable by the incorporation of nanoclays into polyolefins. Additionally, it is significant that these benefits can be realized at clay concentrations consistent with those of common polymer additives, like stabilizers, clarifiers, and colorants.
Characterization and photoinduced properties of photo chromic polymers. 1. Polyesterimides with 4-amino 4´-nitro azobenzene moieties
Authors: Schab-Balcerzak Ewa , Sapich Beate , Stumpe Joachim , Sobolewska Anna , Miniewicz Andrzej 
Published: August 2014

AbstractNovel photochromic polyesterimides (PEIs) with two different types of azobenzene units as side groups have been synthesized from 2,2’-{4-[(4- nitrophenyl)-azo} phenyl]iminobis(ethyl benzene-1,2-dicarboxylic acid anhydride-4- carboxylate) and diamines: 2,4-diamino-4’-methylazobenzene and 2,4-diamino-4’- (trifluoromethoxy)azobenzene. An analogous polyesterimide with one azobenzene group based on 1,3-phenylendiamine has been prepared to compare with these PEIs. Molecular structural characterization for these polymers has been achieved by FTIR, 1H NMR and UV-Vis spectroscopy. These amorphous polyesterimides are thermally stable up to 260°C as follows from the thermogravimetric analysis (TGA). The glass transition temperatures (Tg) for the resulting polyimides have been determined from DSC thermograms and are in the range of 141-210°C. The irradiation with linearly polarized light of an Ar+ laser results in the induction of optical anisotropy within the initially isotropic films. Light induced optical anisotropy in polymer films has been studied by examining the value of generated dichroism using Ar+ laser (λ = 488 nm) and by holographic polarization grating recording performed at λ = 514.5 nm. The value of photoinduced dichroism is in the range of 0.15-0.26. The induction of dichroism and kinetics of grating inscription have been investigated in relation to the presence of the second type of azobenzene group in the polymer and its substitution.
The Attenuated Total Reflection Infrared Analysis of Surface Crystallinity of Polyhydroxyalkanoates
Authors: Hong Shinn-Gwo , Chen Wei-Ming 
Published: August 2014

AbstractThe surface crystallization of three different polyhydroxy alkanoates (PHAs), poly(3-hydroxybutyrate) (PHB), PHB-co-5 weight percent 3-hydroxyvalerate (PHBV5), and PHB-co-12 weight percent 3- hydroxyvalerate (PHBV12), under different processing conditions is analyzed with depth profiling attenuated total reflection spectroscopy (ATR) and differential scanning calorimetry (DSC). The results of ATR indicate that there is a crystallinity distribution on the outer 2 microns thick surface layer. The degree of crystallinity in different penetration depths follows the order of 0.92μ > 0.41μ > 1.70μ for all three hot-pressed PHAs studied and the outer surfaces have a much greater crystallinity than the bulk. The surface crystallinity of specimens is in the order of PHB > PHBV5 > PHBV12 regardless of the different penetration depths analyzed which is consistent with the DSC results. It is also obtained that the effect of annealing in enhancing the crystallization of PHAs is more significant in the surface layer. The surface crystallinity of PHAs obtained after annealing follows the trend of Petri-dish side of solvent-cast PHB > hotpress PHB > air side of solvent-cast PHB > PHBV5 > PHBV12. The difference in crystallinity between the surface and the bulk of PHAs decreases with the addition of 3-hydroxyvalerate but increases after annealing. It is confirmed that the film forming method and the substrate contacted affect the surface crystalline state of PHAs which is attributed to the changes in crystallization conditions in the surface materials.
Highly Stereospecific Polymerizations of 1,3-Butadiene with Cobalt(II) Pyridyl Bis(imine) Complexes
Authors: Kim Jae Sung , Ha Chang-Sik , Kim Il 
Published: August 2014

AbstractA series of prototypical Co(II)-based pyridyl bis(imine) complexes {[2- (ArN=C(Me))2C5H3N]CoCl2} (Ar = 2,6-C6H3Me2, 2,5-C6H3Me2, 2,4-C6H3Me2, 2,3- C6H3Me2) bearing two methyl substituents on each imine aryl group are studied as precatalysts for the homopolymerization of 1,3-butadiene. They showed very high polymerization activities associated with ethylaluminum sesquichloride (EAS) as a cocatalyst. The Co(II) catalysts containing less hindered pyridyl bis(imine) ligands, say [2-(2,3-C6H3Me2N=C(Me))2C5H3N]CoCl2 complex, showed highest activity to give high molecular weight polymers. All catalysts yielded cis-1,4-polybutadienes up to 96.4% with cis-1,4 regular structure.