bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of the curing state of epoxy thermoset systems
Authors: Lachenal Gilbert , Poisson Nicolas , Sautereau Henry 
Published: March 2011

AbstractThe characterization of thermoset networks has been carried out using numerous techniques but accurate determination of the extent of reaction is sometimes difficult. Some of these techniques have ben evaluated rapidly. As example, curing of epoxy‐hardener systems have been investigated by DSC, infrared spectroscopy and other techniques and results were compared. Advantages and drawbacks of each technique are discussed and the risks of obtening misleading results for the kinetic studies or for the determination of reaction extent are underlined. Theses conclusions can be applied to numerous reactive thermoset systems.
Study of the spectral properties of inhomogeneous granular materials
Authors: Ventura CÉLine , Papini Marie 
Published: March 2011

AbstractThe variation of the spectral properties of semi‐transparent (polystyrene: PS), transparent (potassium bromide: KBr) and opacified particles (silver coated silica spheres: Ag‐SiO2) is presented from 0.25 to 20 μm. The spectral properties of binary mixtures PS/KBr and PS/Ag‐SiO2 are also studied.The sensitivity of the spectral properties to the particle diameters causes the near‐normal hemispherical spectral reflectance R to decrease when the particle size increases from 10 to 1800 μm. The addition of KBr transparent particles to PS powders results in an increase in the reflectance values of the mixtures in the near and mid‐infrared wavelength range. Furthermore, the effect of the addition of opacified reflecting particles depends on the wavelength region and on the PS content ([PS]). For < < 1.64 μm, R decreases when [PS] decreases from 1 to 0.56 and then R increases for [PS] values decreasing from 0.56 to 0. For < > 1.64 μm, R decreases when PS content increases from 0 to 1.
Spectroscopic evidence of the polymer tacticity as an important parameter for the configuration of the adsorbed pmma layer
Authors: Grohens Yves , Brogly Maurice , Labbe Clorinthe , Schultz Jacques , Prud'homme Robert E. 
Published: March 2011

AbstractPMMAs with a racemic fraction (fr) ranging from 0.07 to 0.9 and a molecular weight of about 40000 Dalton are adsorbed on aluminum mirrors and alumina powder. The fraction of bonded carbonyl group (p) linked to the substrate by acid‐base interactions is determined by infrared spectroscopy in reflectance mode (IRAS for aluminum mirrors, DRIFT for alumina powder). Calculated values of p range from 0.5 to 0.2 from isotactic to syndiotactic isomers. Ellipsometric thickness (h) of PMMA films are measured on aluminum surfaces and provide values increasing with the average syndiotactic sequence length (ns). Solid state 13C NMR is performed on PMMA adsorbed on alumina powder to provide experimental evidence of interfacial conformational changes. The changes in methylene carbon chemical shift, due to a lowering in the γ‐gauche effect, are more pronounced for isotactic PMMA than for the syndiotactic form. These experimental results lead to the conclusion that the extent of flattening of polymer chains on the substrate depends on the PMMA stereoregularity.
Inelastic neutron scattering studies of polyethylene and N‐alkanes
Authors: Parker Stewart F. 
Published: March 2011

AbstractHigh quality inelastic neutron scattering (INS) spectra of randomly oriented polycrystalline polyethylene, perdeuteropolyethylene and highly oriented polyethylene are presented. The instrumental resolution was significantly better than previous work and has revealed increased detail in the 0 − 600 cm−1 region. For the polycrystalline sample, comparison with the best available dispersion curves shows that these qualitatively reproduce the INS spectrum, apart from the energy of the maximum in the in‐plane C‐C bending mode v5. For the oriented samples, comparison with calculated INS spectra show fair, but not exact, agreement with the experimental spectra.
Application of polymer spectroscopy to the characterization of a sticking gel used in fabrics printing
Authors: Larena Alicia , De Ríol José Manuel 
Published: March 2011

AbstractThe goal of this paper is the making of several physico‐chemical analyses in order to identify the different components which integrate a sticking gel used in fabrics printing. The polymer spectroscopy analyses include infrared spectroscopy and mass spectrometry. Once the main compounds of the sticking gel are found out, we describe the usual components that can be found in a sticking gel formula and each contribution to the final behaviour of the whole, as well as its right adjustment for some given printing conditions, which place this kind of commercial products in an unsurpassable situation, with no rival in this field.
Electron beam curing of methacrylated gelatin studied by EPR and FT‐Raman spectroscopy
Authors: Scherzer Tom , Beckert Annett 
Published: March 2011

AbstractGelatin was modified with glycidyl methacrylate. The methacrylated gelatins were cross‐linked by electron irradiation. The cross‐linking process was studied by FT‐Raman and EPR spectroscopy.
Dextran fatty acid esters as polymeric surfactants with low hemolytic activity
Authors: Bauer Kurt H. , Reinhart Thomas , Stenz Robert 
Published: March 2011

AbstractPractically all low molecular weight surfactants show hemolytic activities. Aside of this serious disadvantage almost all low molecular weight solubilizers cause considerable side effects, particularly during or after parenteral application. Polymeric surfactants, however, usually show no or only very little hemolytic effects. They therefore are supposed not to be able to penetrate neither into cellular or erythrocyte walls nor into phospholipid bilayers, resp., similar bilayer membranes due to their large molecular size. Therefore no decay of biological bilayers should be expected with polymeric surfactants. The only pharmaceutically widely used polymeric surfactants are at the moment polyoxyethylene‐polyoxypropylene block copolymers (poloxamers (INN), Pluronicsr̀ and Pluriolsr̀). Unfortunately they have only poor solubility capacities. In order to find better solubilizing polymeric surfactants, some water soluble dextran fatty acid esters (Ref. 1) were synthesized and tested with respect to their solubilisation capacity and hemolytic activity.Usually the hemolytic activity is tested by standard methods using purified animal or human erythrocyte suspensions. As erythrocytes also contain a relatively high amount of lactose dehydrogenase (LDH), we studied the suitability of the highly sensitive, and in the medical diagnostic well known LDH test, as a supplemental hemolytic determination method (Ref. 2). The advantage of this test is, that there is no need of the time consuming purification and standardization as it is required with the erythrocytes' suspension. It can be performed with original blood and without costly preparations at all.The synthesized dextran fatty acid esters proved themselves as very little hemolytic and, compared with the polyoxyethylene‐polyoxypropylene block copolymers, they show improved solubilisation capacities.
Silylation of cellulose regiocontrolled by bulky reagents and dispersity in the reaction media
Authors: Koschella Andreas , Klemm Dieter 
Published: March 2011

AbstractReaction of cellulose (1) with the bulky thexyldimethylchlorosilane (TDMSCl) leads to regioselectively functionalized silyl celluloses with degree of substitution (DS) up to 2. Uniform 6‐O‐thexyldimethylsilyl cellulose (2) was obtained in ammonia‐saturated aprotic dipolar media, which was unexpected in a heterogeneous reaction. On the contrary, the 6‐O‐selectivity is low under homogeneous conditions in a N,N‐dimethylacetamide (DMA)/LiCl solution, and with an excess of TDMSCl 2,3‐di‐O‐thexyldimethylsilyl cellulose (3) can be synthesized. The polymer structures were characterized by two dimensional NMR spectroscopy after subsequent methylation (polymers 4 and 5), desilylation (polymers 6 and 7) and acetylation (polymers 8 and 9) as well as by HPLC after chain degradation of 4 and 5 to the complementary methyl glucoses.
NMR studies of chiral discrimination by phenylcarbamate derivatives of cellulose
Authors: Okamoto Yoshio , Yashima Eiji , Yamamoto Chiyo 
Published: March 2011

AbstractChiral recognition mechanism of tris(4‐trimethylsilylphenylcarbamate) (1) and tris(5‐fluoro‐2‐methylphenylcarbamate) (2) of cellulose which are effective chiral stationary phases for HPLC were investigated using NMR spectroscopy. The phenylcarbamate derivatives are soluble in chloroform and exhibited chiral discrimination for several enantiomers in NMR as well as in HPLC. Especially, enantiomers of 2,2'‐dihydroxy‐1,1'‐binaphthyl (4) were distinctly discriminated by 2 in 1H and 13C NMR spectroscopies. The binding geometry and dynamics between 2 and the enantiomers of 4 were investigated on the basis of spin‐lattice relaxation time, 1H NMR titrations, and intermolecular NOEs in the presence of 2. These NMR data were fully consistent with the chromatographic elution order. On the basis of these results, combined with molecular modeling, the chiral discrimination mechanism is proposed.
Chemical stability of some model polysaccharides
Authors: Franz Gerhard , Feuerstein Ulrike 
Published: March 2011

AbstractA series of different Polysaccharides with actual or potential medicinal or industrial utilization such as linear fructans of the inuline type, branched fungal ß‐1.3, 1.6‐glucans, galactomannans of the guar type, acidic polysaccharides such as alginates, pectins were submitted to experimental stress‐ and non stress conditions. The resistance to humidity, thermal degradation, pH influence and microbial decomposition was studied by measuring the relative viscosity, reduction in DP values, degradation of specific conformations and glycosidic linkages.It could be clearly shown that most polysaccharides are stable at room temerature in a dry environment. At increased temperature even in the absence of water, polymer decomposition was documented. Polysaccharide solutions, when stored under thermal stress (40°, 60°, 80°C), showed structure dependent rapid progress in degradation of primary and secondary structures. The kinetics of these decompositions were measured over prolonged periods in order to give a practical background for the utilization of such polymers in pharmaceuticals, cosmetics and food products.
Segmented polymers — A new class of doped non‐conjugated polymers with enhanced electrical conductivity
Authors: Schopov Ivan , Sinigersky Vesselin 
Published: March 2011

AbstractA new class of segmented non‐conjugated dopable polymers, built up from short conjugated blocks connected with flexible chains (spacers), has been proposed. After the redox reaction of doping these polymers exhibit properties similar to those of the fully conjugated polymers and increase considerably their electrical conductivity. A solid state polymer effect has been observed. It has been found that the conjugated building units (biphenyl, diphenyl ether and 1,3,4‐oxadiazole) do not interact with the dopant when included in a low molecular weight substance. When these units are incorporated in a polymer chain they change their reactivity and the polymer can be doped. The doping process takes place only when the polymer is in the solid state and the nature of this phase is of considerable importance. The phenomenon observed, i.e. doping of non‐conjugated polymers with segmented structure could be explained with a favourable arrangement of the conjugated blocks in the solid phase, leading to enhanced π‐π ‐ interaction (equivalent to extended conjugation). By the collective interaction of several conjugated blocks with the dopant the polymer is partially oxidized and charge carriers are formed. The result is enhanced electrical conductivity.
Progress in controlled polymerization and design of novel polymer architectures
Authors: Baumert Martin , Frey Holger , Hölderle Matthias , Kressler Jörg , Sernetz Friedrich G. , Mülhaupt Rolf 
Published: March 2011

AbstractRecent developments of new synthetic methods are stimulating the design of new polymers. Modern generations of highly active and selective transition metal catalysts give excellent control on molecular weight, regio‐ and stereoregularities, long‐ and short‐chain‐branching, polymer crystallization, and morphology of olefin, diene, cyclolefin, and styrene polymers. Ethene is copolymerized with polar comonomers such as carbon monoxide and acrylates in new low pressure processes. Catalytic coupling reactions of aromatic halogen compounds and bisphenols afford rigid polyarylenes. „Living” radical polymerization (“TEMPO” and “ATRP”) produce a wide range of telechelics, block copolymers and cascade macromolecules. In reactive processing oxazoline‐mediated coupling reactions are the key to melt diversification of well‐known polymers. Supramolecular concepts are being applied to tailor hybrid polymers and nanocomposites. Precision in polymer synthesis is the key to new materials with wide application range.
Monte Carlo simulations of the polymer glass transition: From the test of theories to material modeling
Authors: Paul Wolfgang , Binder Kurt , Wolfgardt Mathias , Baschnagel Jörg , Tries Volker 
Published: March 2011

AbstractWe present results on the glass transition in polymer melts using Monte Carlo simulations of the bond fluctuation lattice model. There are two questions we address in this work. What is the temperature dependence of the entropy density in such a model polymer melt and how well is it described by theories like the Gibbs‐DiMarzio theory of the glass transition? And to what degree is one able to map the Hamiltonian of such an abstract lattice model onto a specific polymer material and use it to model the large scale and long time properties of a realistic polymer melt?
Neutron spin echo investigations in the α and β relaxation regime of polybutadiene
Authors: Richter D. 
Published: March 2011

AbstractThis short review presents quasielastic neutron scattering and dielectric experiments on the α and βslow relaxation in polybutadiene. Exploiting the momentum transfer dependent dynamic structure factor, spatial information about the underlying molecular motions is obtained. While the βslow process reveals itself as a local jump with average jump distances of about 1.5 Å, the α relaxation is diffusive and occurs statistically independently from the βslow process. With this result a consistent interpretation of dielectric spectra on the same polymer is achieved.
Significance of different modes in dynamics of chains in a dense medium
Authors: Erman Burak 
Published: March 2011

AbstractSingular Value Decomposition technique is used to decompose the trajectory of the fluctuations of atom positions into their modes for a chain of fifty bonds embedded in a fluctuating environment. The temperature of the environment is changed according to a Monte Carlo Metropolis scheme. Results show that at low temperatures only a few modes are significant, these being the slowest ones. For high temperatures, on the other hand, higher modes corresponding to fast fluctuations of atom positions are significant as well.
The control of reactions in the synthesis of tailored polycondensates
Authors: Maréchal Ernest 
Published: March 2011

AbstractThis lecture deals with some problems connected to the synthesis and the characterization of tailored polycondensates. They will be illustrated by examples mainly from our laboratory and bearing on block‐copolycondensates, macrocycles and some structures obtained by enzymatic catalysis. We will particularly emphasize the analysis of the structures and of the eventual side reactions.
Organometallic reactions as tools to build new metal‐containing conjugated polymers
Authors: Lavastre O. , Even M. , Troccon C. , Dixneuf P. H. , Pacreau A. , Vairon J‐P. 
Published: March 2011

AbstractBy using organometallic reactions like Pd‐catalyzed C‐C coupling, metal‐carbon bond formation and silicon‐carbon bond cleavage, novel carbon‐rich organometallic monomers HC≡C‐C6H4‐C≡C‐[M]‐C≡C‐C6H4‐C≡CH ( [M] = ‐Ru(dppe)2‐ and (η5‐C5H4)2Fe) and organic monomers H‐(C≡C‐C6H4)X‐C≡CH (x = 1 to 3) have been obtained. They have been used for the design of novel homo and hetero metal‐containing polymers via organometallic polycondensation reactions based on quantitative metal‐carbon bond formation.
Synthesis of hydrolytically stable phosphorus‐containing polymers via polycondensation and their utilization in polymer blends
Authors: Srinivasan Satya , Kagumba Lawino , Riley Daniel J. , McGrath James E. 
Published: March 2011

AbstractAmorphous polyarylene ether homo‐ and copolymers were synthesized which were based upon bisphenol A and either 4, 4'‐dichlorodiphenylsulfone, 4, 4'‐difluorobenzophenone or 4, 4'‐difluorodiphenyl phenylphosphine oxide. Solution blends were prepared from these homo‐ and copolymers with linear bisphenol A based polyhydroxyether, which was used as a model for the epoxy or vinyl ester thermosetting matrix resins for composite materials. It was observed that transparent, single Tg blends could be prepared from the phosphine oxide containing homopolymer and a 50/50 phosphine oxide/dichlorodiphenylsulfone copolymer. The other homopolymers produced materials with two Tg's, implying that they were definitely phase separated systems. Thermogravimetric analysis was also conducted and the phosphine oxide blends produced high char yields suggesting utilization in fire‐resistant applications. The miscibility of the phosphine oxide material has been attributed to specific hydrogen bonding interactions observed between the phosphine oxide bond and the secondary hydroxyl group in the polyhydroxy ether. This hydroxyl functionality is also present in the epoxy and vinylester precursors and it is suggested that these materials could be utilized as interface sizings for carbon fibers, which would produce a graded microstructure between the fiber and the polymer matrix systems.
Poly(aryl ether phenylquinoxalines) via anionic ring opening polymerization of macrocycles
Authors: Srinivasan S. , Hedrick J. L. , Chan K. P. , Hawker C. J. , Twieg R. 
Published: March 2011

AbstractA cyclic poly(aryl ether phenylquinoxaline) was prepared via the self‐polymerization of 1 in an N‐methyl‐2‐pyrrolidone (NMP) solution containing base using a pseudo‐high dilution polymerization condition. The macrocycle formation of 1 was carried out in the presence of potassium carbonate in a NMP/toluene solvent mixture at a solids content of 1%. The water generated by phenoxide formation was removed as an azeotrope with toluene 170 °C. A concentrated solution of the macrocycle was added to the reaction mixture over an 8 hour period. The reaction was allowed to proceed for an additional 24h to ensure quantitative reaction. A number of characterization techniques were used to study the cyclization of 1 including GPC, HPLC, H NMR and matrix‐assisted laser desorption ionization (MALDI) mass spectroscopy. The MALDI‐TOF mass spectrum of the cyclization of 1 clearly showed that a mixture of macrocycles is obtained, with the expected distribution of molecular weights. Facile ring opening polymerization of the cyclic poly(aryl ether phenylquinoxaline) oligomers was accomplished with a nucleophilic initiator. High polymer was obtained for each polymerization temperature (η = 0.4–0.5 dl/g in NMP), however, prolonged reaction time resulted in significant gel formation. The Tg's were high and commensurate with the high molecular weight linear analog (250 °C).
TNT‐Based condensation monomers and polymers
Authors: Rusanov Alexander L. , Komarova Ludmila G. , Sheveleva Tatyana S. , Prigozhina Marina P. , Shevelev Svyatoslav A. , Dutov Michai L. D. , Vatsadze Irina A. , Serushkina Olga V. 
Published: March 2011

AbstractNew aromatic diamines were obtained on the basis of available and inexpensive 2, 4, 6‐trinitrotoluene (trotyl, TNT). Monomers obtained were used for the preparation of the new organo‐soluble polyimides containing thiophenoxy and phenoxy side groups.
Structure development during sol‐gel process in organic‐silica networks
Authors: Matêjka Libor , Pleštil Josef 
Published: March 2011

AbstractTwo types of the organic‐silica hybrid networks were prepared and their formation and structure were studied in dependence on reaction conditions. The silica phase was formed by the sol‐gel process from tetraethoxysilane (TEOS) or alkoxysilane endcapped prepolymers. The organic phase was composed of linear poly(oxypropylene) chain or the epoxide network arising by curing the diglycidyl ether of Bisphenol A (DGEBA) with poly(oxypropylene)diamine. Fast development of the structure during polymerization was followed by the in‐situ small‐angle X‐ray scattering measurement. One‐ and two‐stage polymerization procedures result in formation of heterogeneous but optically transparent nanocomposites with different structures.
Hyperbranched polyesters and polyamides by the ABX polycondensation process
Authors: Brenner Axel R. , Schmaljohann Dirk , Voit Brigitte I. , Wolf Dieter 
Published: March 2011

AbstractSeveral hyperbranched polyesters with aliphatic and aromatic structural units and one hyperbranched polyamide were prepared by a ABX type polycondensation process in the melt or in highly concentrated solutions at temperatures above 150 °C. The structure of these polycondensates were determined and the polymer properties were analyzed. The hyperbranched polyesters have a degree of branching close to 50% and no indication of side reactions during polycondensation were found. The polyamide structures are more complex and analogous perfectly branched polyamides dendrimer segments up to generation four had to be used as model compounds in order to study structural defects. All hyperbranched polycondensates are fully soluble in polar solvents and exhibit low solution viscosities.
Polycondensation route leading to poly(alkylene phosphate)s
Authors: Pretula Julia , Kaluzynski Krzysztof , Szymanski Ryszard , Penczek Stanislaw 
Published: March 2011

AbstractA polytransesterification method of preparation of the high‐molecular‐weight poly(alkylene H‐phosphonates) ‐ polymers bearing a reactive ‐OP(O)(H)O‐units, is described:magnified imageMechanism of transesterification involves mostly ‐OP(O)(H)O⊖, Mt⊕ “growing species”. The polyphosphonates were converted into a number of derivative polymers, like poly(alkylene phosphates), prepared by a direct oxidation, without decreasing of the DPn of the parent polymers.
Molecular composites of polyimide/poly‐n‐vinylpyrrolidone by in‐situ polycondensation
Authors: Wu Meiyan , Yuan Yumin 
Published: March 2011

AbstractThe molecular composites of polyimide (PI) with poly‐n‐vinylpyrrolidone (PVP) were successfully synthesized by in‐situ polycondensation of the rigid polymer in the matrix polymer solution. A strong acid‐base interaction between the polyamic acid (the precursor of PI) and the PVP was confirmed experimentally. By this specific interaction the miscibility of PI with PVP was substantially improved. The PI dispersed in the PVP matrix polymer on a molecular level or nearly molecular level.