bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemistry and biochemistry of hemicelluloses: Relationship between hemicellulose structure and enzymes required for hydrolysis
Authors: Puls Jürgen 
Published: March 2011

AbstractThe lignified plant cell wall is a composite material in which cellulose, hemicelluloses and lignin are in tight association. Xylans constitute the predominant hemicellulose of hardwoods and straw, wherease galactomannans represent the largest hemicellulose fraction in softwoods. Naturally occuring hemicelluloses, commercially available hemicelluloses and xylans and mannans from technical processes have distinct differences with respect to degree of polymerization and extent of branching. In principle, naturally occuring hemicelluloses carry more side chains compared to those which have been extracted with alkali or under pressure and heat. The presence or absence of substituents is also reflected by the enzymes required for complete hydrolysis. The action of the depolymerizing xylanases and mannanases may be partly dependent on debranching enzymes. Special empasis is therefore given on the substrate requirements of the so‐called accessory enzymes (i.e. α‐glucuronidase, α‐arabinosidase, α‐galactosidase, acetyl‐ and phenolic acid esterase) as well as on synergy effects with the depolymerizing enzymes.
Polymer‐solvent interaction of molecular dispersed and supramolecular structures of cellulose urethanes
Authors: Klohr Erik , Zugenmaier Peter 
Published: March 2011

AbstractInvestigations in dilute, semidilute and highly concentrated solutions have been carried out to characterize cellulose triphenylurethane derivatives as solute. In dilute solutions molecular dispersed chains were found with different Kuhn segment lengths depending on the solvent as well as on the placement of the substituents at the phenyl ring. Elongated, reversible clusters are formed in the semidilute concentration range and have to be considered as building blocks of the helicoidal cholesteric structure in highly concentrated solutions. Since all theoretical descriptions for the lyotropic liquid crystalline state consider the Kuhn segment length as basic quantity, it is not surprising that these theories fail to predict the isotropic‐anisotopic phase transition correctly.
Supramolecular architectures of cellulose derivatives
Authors: Schulze M. , Seufert M. , Fakirov C. , Tebbe H. , Buchholz V. , Wegner G. 
Published: March 2011

AbstractSeveral cellulose derivatives belong to a special class of polymers called hairy‐rod macromolecules which are used to generate well‐defined supramolecular architectures by the Langmuir‐Blodgett (LB) technique. In particular trimethylsilyl cellulose (TMSC) forms monomolecular films on the Langmuir‐trough and is transferred onto hydrophobic substrates with a constant transfer ratio, as it does not undergo chemical changes in the film‐building process. Silylated celluloses was regenerated which represents a convenient method for the generation of homogeneous ultrathin films with hydrophilic surfaces. The adsorption of polymers and dyes as well as biomolecules onto regenerated and modified cellulose LB films have been studied. In addition, chemical reactions, such as cycloaddition, desilylation and crosslinking reactions within single monolayers have been performed.
Monte carlo calculations of second virial coefficients of chain molecules
Authors: Freire Juan J. , Rubio Ana M. , Poncela Antonio 
Published: March 2011

AbstractMonte Carlo calculations have been performed for different types of chain molecules whose units interact through Lennard‐Jones potentials. From the averaged Mayer function, we have evaluated the intermolecular two‐body cluster integral, obtaining results for second virial coefficients. We have investigated the following points: a) the site modelization of alkanes by comparison of our results with gas phase data of different linear and branched alkanes and their mixtures. b) the prediction of interpenetration factors for flexible linear and star polymer chains in a good solvent (or excluded volume conditions). c) the determination of the theta point for a model of flexible polymer chains and the comparison of data for finite chains with theoretical predictions.
Phase behavior of diblock copolymers; pressure and temperature dependence studied by small‐angle neutron scattering
Authors: Mortensen Kell , Almdal Kristoffer , Schwann Dietmar , Frielinghaus Henrich 
Published: March 2011

AbstractThe structure factor of a poly(ethylene‐propylene)poly(dimethylsiloxane) diblock copolymer has been measured by SANS as a function of temperature and pressure. In contradiction to the random phase approximation the conformational compressibility exhibits a pronounced maximum at the order‐disorder phase transition. The phase boundary shows an unusual shape: with increasing pressure it first decreases and then increases. Its origin is an increase in, respectively, the entropic and the enthalpic part of the Flory‐Huggins interaction parameter. The Ginzburg parameter describing the limit of the mean‐field approximation is not influenced by pressure.
Surface anchored polymer: Role in adhesion and friction
Authors: Léger Liliane 
Published: March 2011

AbstractWe present an investigation of thin polymer layers formed by either strong adsorption or end grafting on a surface or an interface. Depending on the kind of surface attachment, different internal organisations of the chains are observed: either polydisperse loops for adsorbed layers, or almost monodisperse tails in the case of grafting. The molecular parameters of the layer (length and surface density of anchored chains) and the molecular organisation inside the layer govern the ability of the surface anchored chains to be swollen by a good solvent or to penetrate into a bulk polymer, either a melt or a cross‐linked elastomer, three properties which have been characterised through neutrons reflectivity techniques. We then analyse how the ability of the surface anchored chains to penetrate into a bulk polymer, entangle with it, and then be deformed when this bulk polymer is mechanically solicitated, are key parameters which govern adhesion and friction properties.
Interactions between surfaces coated with solvophobic and solvophilic homopolymers
Authors: Pickett Galen T. , Balazs Anna C. 
Published: March 2011

AbstractUsing scaling theory, we investigate the interaction between two planar surfaces that are coated with both A and B homopolymers. The polymers are tethered by one end and grafted at relatively low densities. The B chains are chosen to be solvophobic, while the A polymers are solvophilic. Calculating the energy of interaction versus distance profile, we find that the curve shows a wide attractive region as the surfaces are compressed. The features of this profile can be tailored by varying the length and grafting densities of the different chains. Our results provide guidelines for controlling the interaction between polymer‐coated colloidal particles.
Polycondensation design of tailored high performance polymers
Authors: Vygodskii Yakov S. , Nesmeyanov A. N. 
Published: March 2011

AbstractThe ways of the preparing of high performance polymers (HPP) having tailored properties are considered. Common two and one step methods of such polymers synthesis are compared. Some peculiarities of one step polycyclization including the catalytic processes are discussed. Matrix polycondensation leading to the formation of HPP and their blends is analysed. The synthesis of some functional polymers (polyamides and polyamides) having quinuclidine moieties is described.
High pressure synthesis of polyimides and related polymers
Authors: Imai Yoshio 
Published: March 2011

AbstractThis paper reviews our current studies on the high pressure synthesis of polyimides and related condensation polymers. After a brief introduction of the solid‐state thermal synthesis of polyimides starting from nylon‐salt‐type monomers, the paper deals with the high pressure synthesis of polyimides, the preparation of polyimide‐silica hybrid materials by the combination of the above synthetic method for polyimides and the sol‐gel reaction for silica synthesis, and the high pressure synthesis of polybenzoxazoles and addition‐type polyaminoimide.
Synthesis of poly(cyclodiborazane)s by allylboration polymerization of dicyano compounds with trimethallylborane
Authors: Chujo Yoshiki , Tomita Ikuyoshi 
Published: March 2011

AbstractAllylboration polymerization of α, ω‐dicyanoalkanes with trimethallylborane produced the corresponding poly(cyclodiborazane)s in high yields. This polymerization includes the allylboration reaction of cyano groups and the following dimerization of iminoborane species. The intermediate iminoborane species were detected by IR measurement. The poly(cyclodiborazane)s obtained were found to be more stable toward air than those prepared by allylboration polymerization using triallylborane.
Synthesis and molecular properties of new poly(naphthalene‐1, 3, 4‐oxadiazole)s
Authors: Lavrenko Peter , Schulz Burkhard , Strelina Irina , Okatova Olga 
Published: March 2011

AbstractPoly[(1, 4‐naphthalene)‐2, 5‐diyl‐1, 3, 4‐oxadiazole] and poly[(2, 6‐naphthalene)‐2, 5‐diyl‐1, 3, 4‐oxadiazole] have been synthesized and investigated in conc. H2SO4, by the flow birefringence method, in comparison with poly[(1, 4‐phenylene)‐2, 5‐diyl‐1, 3, 4‐oxadiazole]. Changes in conformation parameters and optical anisotropy of a chain unit induced by incorporation of the naphthalene groups into the macromolecule backbone have been evaluated.
Enzyme‐catalyzed polyester synthesis in organic medium: Ring‐chain equilibrium
Authors: Berkane Christophe , Mezoul Gilles , Lalot Thierry , Brigodiot Maryvonne , Maréchal Ernest 
Published: March 2011

AbstractEnzyme‐catalyzed synthesis of aliphatic, unsaturated and semi‐aromatic polyesters from methyl diesters and diols was carried out in toluene at 60°C in the presence of supported lipases. Whatever the monomer structure, rings were formed concurrently to linear chains excepted when dimethyl fumarate was used. The yield of rings depends on several parameters such as the monomer structure and the initial concentration of the reactive functions and strongly influences the average molar masses of the unfractionated samples. For aliphatic, unsaturated and semi‐aromatic polyesters, the molar cyclization equilibrium constants (K) were determined and it would appear that the molar distribution of the ringed species obeys Jacobson‐Stockmayer equation: LnK = LnB − 5/2 Lnn, where B and n represent a constant and the number of monomer units of each type in the ring, respectively.
Liquid crystal thermosets from mesogenic isocyanates and epoxides
Authors: Mormann Werner , Irle Christoph 
Published: March 2011

AbstractLiquid crystal thermosets from mesogenic diisocyanates are described. Aromatic diisocyanates having the functional groups directly attached to the aromatic rings form isotropic thermosets with incomplete conversion due to crystallisation. Diisocyanates with flexible spacers and copolymers with mesogenic diepoxides have been synthesised and polymerised to overcome the geometrical restrictions which prevent the formation of a mesophase. The oxazolidinone moiety stabilizes a mesophase which was demonstrated with model compounds. Both approaches yield liquid crystal thermosets. The influence of the structure of the comonomers on the mesophase stability of isocyanurate/oxazolidinone networks was investigated.
Morphological and phase behavior studies of uniquely derived epoxy/polyimide semi‐IPNS
Authors: Gaw Kevin , Suzuki Hironori , Jikei Mitsutoshi , Kakimoto Masa‐Aki , Imai Yoshio 
Published: March 2011

AbstractInterpenetrating networks (IPNs) of polyimide (PI) and epoxy were made by reaction of epoxy (EGEBA) with a polyamic acid (PAA). In addition, epoxy was cured with both a monomeric hardener, pyromellitic dianhydride (PMDA) and PAA to see changes in the morphology and glass transitions caused by the monomeric hardener. Due to “molecular interlock” of the individual polyimide molecules that was brought about by the PAA‐epoxy reaction, systems cured with only PAA did not phase separate and showed a significant increase in Tg when compared to PMDA cured epoxy. All PMDA cured systems phase separated By dynamic mechanical analysis (DMA), it was confirmed that all systems containing over 20% PAA had two glass transitions. The extent of miscibility of the polyimide into the epoxy was relatively constant. PAA cured epoxy systems showed phase miscibility over all compositions and cure regimes
Principles of theoretical description of microstructure of linear condensation polymers
Authors: Kuchanov Semion I. 
Published: March 2011

AbstractKey ideas of general original approach to the theoretical consideration of monomer sequence distribution problem are formulated for linear condensation heteropolymers showing either isomerism due to different fashions of monomer unit alternation in macromolecules of a copolymer or constitutional isomerism resulting from different orientation of asymmetric monomer units in polymers.
Polycarbosilanes containing siloxy and/or silanamine units by polycondensation using hydrosilylation
Authors: Jallouli Aref , Lestel Laurence , Tronc Frédéric , Boileau Sylvie 
Published: March 2011

AbstractPoly(1,1‐dimethyl‐1‐silylethylene): ‐(SiMe2‐CH2‐CH2)‐n was prepared by polycondensation of HSiMe2‐CH2‐CH2‐SiHMe2 (A) with CH2=CH‐SiMe2‐CH2‐CH2‐SiMe2‐CH=CH2 (B) under suitable hydrosilylation conditions. Functional oligomers with either two SiH or two Si‐CH=CH2 end groups were obtained by using an excess of A or B respectively. These bifunctional oligomers were used as precursors for the preparation of well‐defined networks by reaction with different tetrafunctional crosslinking agents such as D4H, D4Vib) and tetravinylsilane (TVS). They were also used for the preparation of multiblock copolymers by reaction with dimethylsiloxane oligomers. Alternating copolymers were obtained from monomers containing siloxy or silanamine units. Thermal properties of these polymeric materials are presented.
Polycondensation of cyclodextrins with epichlorohydrin. Influence of reaction conditions on the polymer structure
Authors: Renard E. , Sebille B. , Barnathan G. , Deratani A. 
Published: March 2011

AbstractA series of water‐soluble polymers was synthesized by polycondensation of cyclodextrin with epichlorohydrin under basic conditions. We studied their molecular distribution as a function of molar ratios of reactants. NaOH concentration showed that very high molecular averages (Mw > 106) can be obtained. The substitution patterns were determined by 13C NMR analysis and standard methylation analysis of polysaccharides. The formation of side chains and bridges consisting of sequences of poly(2‐hydroxypropyl)ether units were demonstrated by electrospray ionization mass spectrometry and gas liquid chromatography‐mass spectrometry. The predominant position of substitution depends on the NaOH concentration.
Kinetics of polycondensation in an industrial environment
Authors: Blondel Philippe , Briffaud Thierry , Werth Michael R. G. 
Published: March 2011

AbstractThe influence of industrial reaction conditions on the kinetics of the polycondensation of polyamides is discussed. For analysis reasons the overall process was subdivided into individual kinetic phases. It will be shown that the basic features of the reaction rate in the final reaction stage can be explained assuming second order kinetics combined with a superposed reaction equilibrium. The influence of non‐stoechiometry on the reaction rate is also demonstrated.
1H, 13C, 14N and 15N NMR Study of copolycondensates obtained by 1, 3 dipolar cycloaddition of α, ω‐diazidoalkanes with 1, 1'‐(methylene di‐4, 1‐phenylene) bismaleimide, with N, N'‐1, 4‐phenylene dimaleimide and with isopropylidene‐1, 4‐phenylene dimethacrylate
Authors: Nguyen Hung Anh , Cheradame Hervé , Belleney Joël , Maréchal Ernest 
Published: March 2011

AbstractCopolycondensates of α, ω‐diazidoalkanes with 1, 1'‐(methylenedi‐4, 1‐phenylene) bismaleimide, with N, N'‐1, 4‐phenylene dimaleimide and with isopropylidene‐1, 4‐phenylene dimethacrylate were synthetized using 1, 3 dipolar cycloaddition reaction (DCA). Their structures were determined by 1H, 13C, 14N, 15N NMR. The results show that at high temperature (150°C), the copolycondensates present a mixture of triazoline/succinimide, of aziridine/succinimide, of enamine/maleimide and of anil/succinimide junctions. At low temperature (20°C), only the triazoline structure is formed. A reaction scheme is proposed via two reactions, DCA and nitrene formation, occuring simultaneously and independently.
Nouveaux Élastomères de polyuréthanes dérivés d'aminoacides
Authors: Fontaine Laurent , Ménard Laurent , Cayuela Olivier , Brosse Jean‐Claude , Sennyey Gérard , Senet Jean‐Pierre 
Published: March 2011

AbstractSynthesis and characterization of new polyurethane elastomers with rigid blocks derived from aminoacids have been achieved by polycondensation using poly(tetramethylene oxide) (PTMO) as a soft segment. Aminotelechelic oligopeptides or pseudopeptides were used in the hard block, eventually in association with lysine diisocyanate (ethyl 2, 6‐diisocyanatohexanoate, LDI). Physicochemical characteristics of the so obtained materials, especially good filmmaking properties, allow their use as biomaterials of reduced toxicity.
Thermoplastic elastomers by “criss‐cross”‐cycloaddition polymerization
Authors: Maier Gerhard , Fenchl Andrea 
Published: March 2011

AbstractSegmented blockcopolymers were prepared via the condensation of telechelic precursors. “Criss‐cross”‐cycloaddition of an aromatic aldazine with a diisocyanate gave telechelics with isocyanate functions at both ends. These prepolymers were reacted with α, ω‐dihydroxytelechelic aliphatic polyethers. The cyclo‐addition‐polymers served as hard segments with softening temperatures between 100°C and 150°C. The resulting segmented blockcopolymers exhibited microphase separation. Depending on the length and fractions of hard and soft segments, the mechanical properties varied from tough thermoplastics to soft elastomers with ultimate elongations above 800%.
Synthesis of photoreactive polymers by a distannoxane catalyzed transesterification. Polycondensation of α, ω‐dicarbomethoxy‐1, 4‐oligobutadiene with a photoreactive diol
Authors: Campistron Irène , Reyx Danièle , Hamza Mohammed , Oulmidi Abdelkader 
Published: March 2011

AbstractOptimal conditions for distannoxane catalyzed transesterification of methyl esters with benzylic alcohols were established by studying the polycondensation of hex‐3‐ene‐1, 6‐bis(methyl oate) (1) with 1, 4‐bis(hydroxymethyl)benzene (2). α, ω‐Dicarbomethoxy‐1, 4‐oligobutadiene (3) was obtained by cross metathesis between cycloocta‐1, 5‐diene and 1. The synthesis of 1, 4‐bis[4‐(hydroxymethyl)cinnamoyl]‐benzene (4) were conducted starting from 4‐(diethoxymethyl)benzaldehyde (5) and 1, 4‐diacetylbenzene. Finally the organosoluble polyester (PE3/4) were synthesized by reacting 3 with 4 and the occurrence of crosslinkings by UV irradiation was checked.
Synthesis and properties of polyurethane macroazo initiators
Authors: Cheikhalard Talal , Massardier Valérie , Tighzert Lan , Pascault Jean Pierre 
Published: March 2011

AbstractThe synthesis of a typical polyurethane macroazo initiator (PUMAI) based on 2, 2'‐azobis(2‐cyanopropanol) (ACP), α, ω‐hydroxy polycaprolactone (PCL) and 4, 4'‐methylene diphenyl diisocyanate (MDI) occurs in a two stage polycondensation procedure. Kinetics of the reaction between ACP and a monoisocyanate (para‐tolylisocyanate, p‐TI), and the reaction between MDI and PCL were carried out. Reaction rates were determined by a suggested kinetic model. Thermal decomposition of PUMay compared to other azo initiators has been investigated. The kinetic and thermal parameters associated with these initiators were determined by thermogravimetric analysis (TGA).
Biosynthetic and biodegradable polyesters from renewable resources: Current state and prospects
Authors: Steinbüchel Alexander , Gorenflo Volker 
Published: March 2011

AbstractBacterial poly(hydroxyalkanoate)s (PHA) are a complex class of polyesters, and almost one hundred different constituents are currently known. Unfortunately, most of these constituents only occur in the polyesters if specific precursor substrates are provided as carbon source. Recently, however, bacteria and mutants were isolated, which synthesize PHA exhibiting an interesting composition from simple unrelated substrates obtainable from renewable resources provided by the agriculture. This contribution will provide an example how PHA based on 4‐hydroxyvaleric acid can be obtained from bulk chemicals. In addition, some aspects of our current knowledge on the physiological and molecular basis of PHA biosynthesis will be provided.
Biodegradable polyphosphazenes for drug delivery
Authors: Lemmouchi Yahia , Schacht Etienne , Dejardin Stéphane , Vandorpe Joke , Seymour Leonard 
Published: March 2011

AbstractPolyphosphazene derivatives having amino acid ester side groups were prepared by reaction of poly(dichlorophosphazene) with ethyl esters of amino acids. The in vitro degradation studies demonstrated that the rate of degradation depends on the nature of the amino acids. Introducing small amounts of hydrolytically sensitive groups such as depsipeptide ester or hydrolysis‐catalysing moieties, such as histidine ethyl ester co‐substituents, resulted in an increase of the degradation. The rate of hydrolytic degradation of the polyphosphazene material could be controlled by the content of the hydrolytically sensitive side groups or by blending hydrolysis‐sensitive polymers with more stable derivatives. The results obtained from the in vivo implantation of biodegradable polyphosphazenes in mice indicate that the materials are very well tolerated by the animal body. Biodegradable polyphosphazenes have been used as matrix for the design of drug delivery systems. The rate of the in vitro release of mitomycin C from biodegradable polyphosphazenes can be controlled by changing the chemical composition of the polymer or by blending polymers of different chemical compositions.
Polylactides ‐ degradable polymers for fibres and films
Authors: Meinander Kerstin , Niemi Maria , Hakola Jyrki S. , Selin Johan‐Fredrik 
Published: March 2011

AbstractModification of a poly(L‐lactide) (PLLA) base resin, by treatment with peroxides and compounding with plasticisers, yield resins which can be processed by conventional techniques and equipment to thin blown films, fibres and nonwoven fabrics having properties comparable to those of corresponding PP and PE samples. Film samples have tensile strength between 30 and 50 MPa, elongation at break around 250%, and puncture resistance, measured as dart drop values, of 12 g/μm. Fibres can be spun to filaments or directly to nonvowen fabrics by spun‐bond techniques. These fabrics have mechanical properties comparable to polypropylene materials. The polymer products are readily degraded in a compost to carbon dioxide, water and biomass.
Design and development of biodegradable polymeric poly(carboxylic acids) as co‐builders for detergents
Authors: Swift Graham , Freeman M. B. , Paik Y. H. , Simon E. , Wolk S. , Yocom K. M. 
Published: March 2011

AbstractThis paper outlines the requirements for truly acceptable biodegradable water‐soluble polymers, in effect establishing the goals of a polymer synthesis program. The deficiencies of the current products are thus clearly identified. A brief review of the redundant approaches that have been made to develop biodegradable polymers will be followed by a description of the chemistry and environmental properties of poly(aspartic acid) which has been identified as meeting all the technical requirements for a biodegradable polymeric co‐builder for detergents.