bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cooperative self‐assembling in statistical copolymers: a new approach to high‐temperature thermoplastic elastomers
Authors: Hellmann Jörg , Hilger Christopher , Stadler Reimund 
Published: April 2003

AbstractBased on previous work, where it was shown that 4‐urazoylbenzoic acid (U4A) groups, which are attached statistically to polybutadiene, form ordered supramolecular arrays in the unpolar polymer matrix, the present work describes the synthesis of a new molecular building block capable of self‐assembling in the unpolar polymer matrix. 5‐Urazoylisophthalic acid (U35A) groups attached to 1,4‐polybutadiene chains cause the formation of a thermoplastic elastomer of improved properties. The clusters of functional groups show an endothermic transition. The melting temperature increases for low levels of modification from 130°C up to 190°C. The mechanical properties (stress–strain and dynamic mechanical) reveal excellent rubbery characteristics and a rubbery plateau which is considerably flatter than those of technical grade thermoplastic elastomers. The IR data indicate that the U35A groups are tetrafunctional with respect to supramolecular self‐assembling. Based on detailed knowledge of the structure of the self‐assembled domains in U4A groups, a model is developed which describes the observed material properties qualitatively.
Mesomorphic flexible chain polymers based on silicon
Authors: Out G. J. J. , Siffrin S. , Frey H. , Oelfin D. , Kögler G. , Möller M. 
Published: April 2003

AbstractPoly(dialkylsiloxane)s and poly(dialkylsilane)s form a similar type of columnar mesophase. Although, the polysilanes are stiffer than polysiloxanes, both classes of polymers may be considered to be flexible due to the ability to form chain‐folded crystals. Chain flexibility rather than the presence of chain stiffness determines whether the columnar mesophase is formed. A certain amphiphilic character does not appear to be required, as polysiloxanes with short side groups, e.g. polydiethylsiloxane display the same mesophase behaviour as polydialkylsilanes with long side chains and other nonpolar flexible chain molecules. The importance of the entropy gain upon conformational disordering is reflected in the increase in temperature stability with increasing alkyl side group length and the absence of mesophase behaviour in the case of the dimethyl substituted polymers
Chemical modification of polymer surfaces: a review
Authors: Penn L. S. , Wang H. 
Published: April 2003

AbstractThe main approaches that have been taken to chemically modify polymer surfaces are introduced and reviewed. These are wet chemical oxidation, plasma treatment, classical organic chemistry, and attachment of polymer chains. The extent to which each of these approaches can produce the specific modifications desired is discussed, and any unwanted effects that commonly occur are cited. Finally, the need for using several methods of surface analysis in concert to obtain adequate surface characterization is described.
Doping of polyaniline with polymeric dopants in solid state, gel state and solutions
Authors: Liao Yun‐Hsin , Levon Kalle 
Published: April 2003

AbstractPolystyrene with different degrees of sulfonation was empolyed as a polymeric dopant for polyaniline. The purpose of using a polymeric dopant is to avoid the migration of a small molecule dopant to increase stability of the doped complex. We applied the polymeric dopant to polyaniline in three different ways: in solid state, in solution and in gel state. In solid state, the conducting form was achieved only through a novel thermal doping method with the increase in temperature and pressure. In solution, the doping process was shown to be dependent on the nature of the solution and also on the molecular weight of the polymer. In the gel form of polyaniline, a polymeric dopant with a surprising low degree of sulfonation was found to be successful in the doping process.
Mechanistic study of thermal behavior and combustion performance of epoxy resins: I homopolymerized TGDDM
Authors: Levchik Sergei V. , Camino Giovanni , Luda Maria Paola , Costa Luigi , Costes Bruno , Henry Yves , Morel Emile , Muller George 
Published: April 2003

AbstractTetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM) undergoes homopolymerization on heating. Intramolecular reactions which compete with crosslinking favor the formation of cyclic structures with increasing thermal and fire resistance of the resin, whereas physical mechanical properties tend to decrease.The mechanism of thermal decomposition of TGDDM is studied by thermogravimetry, differential scanning calorimetry and thermal volatilization analysis with characterization of volatiles evolved and residue left. Thermal degradation of poly‐(TGDDM) starts at 260°C with elimination of water from secondary alcoholic groups which is a typical pathway for epoxy resin degradation. Resulting unsaturations weaken bonds in the β‐position and provoke the first chain breaking at allyl–amine and allyl–either bonds. With increasing temperature, saturated alkyl–ether bonds and alkyl carbon–carbon bonds are broken first, followed by the most stable alkyl–aryl bonds at T>365°C. The combustion performance of TGDDM is discussed on the basis of the thermal degradation behavior.
Synthesis and characterization of thermoplastic copolyesters containing copolymerized azoic dyes
Authors: Po Riccardo , Bornengo Giorgio , DiStefano Letterio , Cavagna Carla , Occhiello Ernesto , Garbassi Fabio 
Published: April 2003

AbstractPoly(ethylene terephthalate) and a series of other amorphous copolyesters based on ethylene glycol and terephthalic/isophthalic or 2,6‐naphthalenedicarboxylic/isophthalic acid mixtures were prepared by melt polycondensation. Comonomers consisting of azoic dyes having two polymerizable functions on the aromatic rings (either one alcoholic and one carbomethoxyl, two alcoholic or two carbomethoxyl groups) were also added, in amounts lower than 1% mol with respect to the sum of diesters used as starting monomers. In these conditions (P<0.1 torr and T=280°C), only few azoic dyes were found to be stable.Among the prepared polymers, those based on dyes having sufficient thermal stability were characterized by differential scanning calorimetry and solution properties. Inherent viscosities suggest that molecular weights are high. Glass transition and melting temperatures as well as mechanical properties of colored polyesters are not affected by the presence of the azoic comonomers. UV–visible spectra of copolyester solutions were registered, and absorption coefficients were correlated with the amount of dye.
Fabrication and spectroscopic characterization of the nanocrystals of poly[5,7‐dodecadiyn‐1,12‐diol bis(n‐butoxycarbonylmethyl urethane)]
Authors: Nalwa Hari Singh , Kasai Hitoshi , Okada Shuji , Matsuda Hiro , Oikawa Hidetoshi , Minami Nobutsugu , Kakuta Atsushi , Mukoh Akio , Ono Katsumichi , Nakanishi Hachiro 
Published: April 2003

AbstractA novel wet water–ethanol‐borne technique of preparing nanocrystals of the poly[5,7‐dodecadiyn‐1,12‐diol bis‐(n‐butoxycarbonylmethyl urethane)], oxoreferred to as poly(4‐BCMU), is reported for the first time. The fabrication of poly(4‐BCMU) nanocrystals with sizes ranging from a few to hundreds of namometers is presented. The spectroscopic analysis of the poly(4‐BCMU) nanocrystals using nuclear magnetic resonance, infrared, optical absorption spectroscopy, gel permeation chromatography and scanning electron microscopic techniques is discussed. A structural characterization at molecular level of the poly(4‐BCMU) constituting the nanocrystals evidences the maintenance of the molecular integrity of the polydiacetylene backbone.
Phthalocyanines and related macrocycles for multi‐electron transfer in catalysis, photochemistry and photoelectrochemistry
Authors: Wöhrle Dieter , Schlettwein Derck , Schnurpfeil Günter , Schneider Gerhard , Karmann Elfriede , Yoshida Tsukasa , Kaneko Masao 
Published: April 2003

AbstractAt different phthalocyanines and related macrocycles it is shown that one‐step, multi‐electron transfer and one‐step, multi‐change of oxidation states occur. At first, the catalytic oxidations of thiols and sulfide in the presence of different Co(II)phthalocyanines are discussed. Thiolates are oxidized to disulfides via a two‐electron transfer whereas the reduction of O2 occurs via a two‐ or four‐electron transfer to H2O2 or H2O. Zn(II) and Al(III)phthalocyanines are efficient sensitizers for the conversion of triplet to singlet dioxygen under illumination with visible light. In the presence of thiolates or sulfides an efficient photo‐oxidation to sulfonic acids or sulfate is observed. The oxidation state of sulfur changes from −2 to +4 or +6, respectively. This process of singlet oxygen reactions finds application in the photodynamic therapy of cancer. The unsubstituted zinc(II)‐phthalocyanine as p‐type molecular semiconductor can efficienfly reduce O2 in photoelectrochemical experiments whereas zinc(II)phthalocyanines with electronwithdrawing groups as n‐type conductors are active in the photoelectrochemical oxidation of thiols. All processes include multi‐electron transfer. The electrocatalytic reduction of CO2 is investigated at electrodes modified with Co(II)phthalocyanine. In particular, the phthalocyanine in a polyvinylpyridine membrane is active, so the CO2 is reduced to CO by multi‐electron transfer. In addition, two photon excitations of a Mg(II)phthalocyanine are presented and some examples are reviewed.
Multi‐electron transfer process of vanadyl complexes for oxidative polymerization of diphenyl disulfide
Authors: Yamamoto Kimihisa , Oyaizu Kenichi , Tsuchida Eishun 
Published: April 2003

AbstractOligo(p‐phenylene sulfide) is synthesized by oxidative polymerization of diphenyl disulfide with oxygen catalyzed by vanadyl acetylacetonate under strongly acidic conditions. The mechanistic studies reveal that the redox cycles of the vanadyl complexes give rise to catalysis through a two‐electron transfer between diphenyl disulfide and molecular oxygen. The VO catalysts act as an excellent electron mediator to bridge a 1.0 V potential gap between the oxidation potential of disulfides and the reduction potential of oxygen. The VO‐catalyzed oxygen‐oxidative polymerization provides pure oligo(pphenylene sulfide)s containing an S–S bond. The polymeric product is of low molecular weight due to the insolubility under these conditions.(N,N′‐ethylenebis(salicylideneaminato))oxovanadium‐(IV), VO(salen), was used as an inert model compound to elucidate the redox chemistry of the vanadium complex. VO(salen) reacts with trifluoromethanesulfonic acid (CF3SO3H) or triphenylmethyl tetrafluoroborate (ϕ3C(BF4)) to form a deoxygenated complex, VIV(salen)2+, and a μ‐oxodinuclear complex, [(salen)VOV(salen)]X2, (X = CF3SO3− or BF4−). The dimerization of VO(salen) is initiated by deoxygenation to produce V(salen)2+ which enters into an equilibrium with a second VO(salen) complex to produce the μ‐oxo dimer. The two‐electron transfer of the μ‐oxo dinuclear vanadium complex is elucidated.
Dipole moments and structure of poly(epoxypropylcarbazole)
Authors: Kuliešius F. , Kriščiūnas V. , Mačkus P.‐K. 
Published: April 2003

AbstractThe mean‐square molecular dipole moments 〈μ2〉 of carbazole, N‐ethylcarbazole and of the sequence of poly(epoxypropylcarbazole) (PEPCa) oligomers of various molecular weights have been evaluated in solutions of these organic compounds in dioxan. For PEPCa the values of 〈μ2〉 have also been determined in the solid state. On the basis of the experimental results and of molecular mechanics calculations it has been shown that the orientation of the lateral group of PEPCa favors noninteracting racemic dyads. The temperature‐dependence of the effective dipole moment of solid PEPCa follows the Onsager theory above 295 K.
Synthesis and structure–property relationships of acrylic core–shell particle‐toughened epoxy networks
Authors: Bécu L. , Sautereau H. , Maazouz A. , Gérard J. F. , Pabon M. , Pichot C. 
Published: April 2003

AbstractThe use of emulsion polymerization to prepare core–shell rubber (CSR) toughening particles with different shell thickness‐to‐core diameter ratios is described. The conditions leading to controlled particle size and morphology are discussed. The particle shell is crosslinked during the synthesis so that its integrity and morphology are maintained upon curing of the epoxy network. The mixing of the CSR particles with the reactive epoxy and the processing of toughened‐epoxy networks are described. The characteristics of each phase and the mechanical properties of the materials are reported. The fracture parameters (Klc, Glc) are discussed in relation to the structure of the CSR‐particles.
Nanocomposite materials from latex and cellulose whiskers
Authors: Favier V. , Canova G. R. , Cavaillé J. Y. , Chanzy H. , Dufresne A. , Gauthier C. 
Published: April 2003

AbstractComposite materials were processed by casting a mixture of aqueous suspensions of latex and microfibrils. These microfibrils, or whiskers, are extracted from a sea animal and are monocrystals of cellulose, with an aspect ratio around 100 and an average diameter of 20 nm. It has been found that the mechanical properties (shear modulus) are increased by more than two orders of magnitude in the rubbery state of the polymeric matrix, when the whisker content was 6% (w/w). This very large effect is discussed on the basis of different types of mechanical models and it is concluded that these whiskers form a rigid network, probably linked by hydrogen bonds. The formation of this network is assumed to be governed by a percolation mechanism.
Electrically conducting polymer colloids and composites
Authors: Vincent Brian 
Published: April 2003

AbstractThe preparation, characterization and properties of aqueous dispersions of electrically conducting polymer particles are described. Three types of such particles have been prepared: polyacetylene, polypyrrole and polyaniline. Particles in the size range 50–500 nm (diameter) and with conductivities generally ≃ 1–10 S cm may be made. Composites of such particles, dispersed in a matrix polymer which is non‐conducting, are also described.
Morphology and properties of semi‐IPNs of polyetherimide and bisphenol A dicyanate
Authors: Lee Bong Keun , Kim Sung Chul 
Published: April 2003

AbstractSemi‐interpenetrating polymer networks (semi‐IPNs) were synthesized from mixtures of polyetherimide (PEI) and bisphenol A dicyanate (BPACY) at different compositions and different cure temperatures. The phase separation behavior during cure was analyzed in terms of glass transtion temperature (Tg) behavior of fully cured semi‐IPNs and the morphology–property relationship was also studied. The mixtures of PEI and BPACY monomer showed upper critical solution temperature behavior and their semi‐IPNs showed sea‐island morphology in 1–14 wt% PEI composition, dual‐phase morphology in 15–19 wt% PEI composition and nodular morphology in 20–60 wt% PEI composition, respectively. The sea‐island morphology was formed via nucleation and growth, while the other morphologies were predominantly formed via spinodal decomposition. Cure temperature did not influence the macroscopic morphology, but the domain size changed with temperature. As cure temperature was increased, the PEI domain size in the sea‐island morphology decreased, while the BPACY nodule size increased in the nodular morphology. Mechanical and thermal properties were so strongly dependent upon the morphology that they changed dramatically near the phase inversion point.
Block copolymers prepared by emulsion polymerization with poly(ethylene oxide)–azo‐initiators
Authors: Tauer K. 
Published: April 2003

AbstractPoly(ethylene oxide)‐b‐poly(styrene) block copolymers were prepared in the form of latex particles by emulsion polymerization of styrene with poly(ethylene glycol)–azo‐initiators as well as with the redox initiation system poly(ethylene glycol)/Ce4+. The emulsion polymerization can be carried out in the absence of additional stabilizers if the chain length of the poly(ethylene glycol) is greater than 40. The latex particles as well as the copolymers were characterized by capillary hydrodynamic fractionation, 13C‐nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy. By 13C‐NMR spectroscopy a side reaction of the primary radicals arising from the azo‐initiator was found which can contribute to the low efficiency of azo‐initiators in emulsion polymerization.
Polymeric surfactants in latex technology: polystyrene–poly(ethylene oxide) block copolymers as stabilizers in emulsion polymerization
Authors: Mura Jean‐Luc , Riess Gérard 
Published: April 2003

AbstractPolystyrene–poly(ethylene oxide) PS–PEO di‐ and triblock copolymers have been used as stabilizers in the emulsion polymerization of styrene and styrene–butylacrylate for the preparation of “hairy latexes”. The polymerization kinetics and the efficiency of these polymeric surfactants were correlated with the molecular characteristics of the block copolymer. It was shown that the efficiency decreased with increasing molecular weight and PS content of the block copolymer.The PEO frige, with a thickness of 4–25 nm, on the latex particle surface could be characterized and it was shown by differential scanning calorimetry (DSC) that water is strucured in that PEO layer. Film formation with “hairy latexes” was also examined both by DSC and thermomechanical analysis. The properties and application possibilities, such as in controlled latex flocculation, have been reviewed.
Protein adsorption on polystyrene latex particles
Authors: Norde Willem , Gonzalez Francisco Galistéo , Haynes Charles A. 
Published: April 2003

AbstractProtein adsorption is the net result of various types of interaction between the different components present in the system, i.e. the sorbent surface, the protein(s), the solvent and any other solutes such as low molecular weight electrolyte. In this paper methods and techniques will be discussed to study the mechanism of protein adsorption on, in particular, colloidal particles. The discussion is based on experimental data obtained with relatively simple systems that contain one well‐defined protein and well‐characterized polystyrene latexes. Thus, the adsorption behavior of lysozyme and α‐lactalbumin are compared, emphasizing the role of structural rearrangements in the protein molecule.
The effect of pigments on the crystallization and properties of polypropylene
Authors: Silberman A. , Raninson E. , Dolgopolsky I. , Kenig S. 
Published: April 2003

AbstractThe effect of pigments of different chemical compositions on the crystellization process of PP was studied by means of differential scanning calorimetry in isothermal mode. The Avrami equation was applied to obtain the crystallization parameters of polypropylene with different pigments.Lipatov's equations were applied for evaluation of the thickness and volume content of the transition layers. Results show that pigments affect not only the degree of crystallinity but also the structure of the amorphous phase and the integrity of the crystalline/amorphous interphase. Finally, the morphology and mechanical properties of pigmented polypropylene were studied in view of the different chemical compositions of the various pigments.
Making polymer concrete and polymer mortar using synthesized unsaturated polyester resins from poly(ethylene terephthalate) waste
Authors: Abdel‐Azim Abdel‐Azim A. , Attia Ibrahim A. 
Published: April 2003

AbstractDepolymerization of poly(ethylene terephthalate), PET, waste was studied in the presence of manganese acetate catalyst and propylene glycol (PG) at different weight ratios. The glycolyzed products were analyzed for hydroxyl value and the amount of free glycol. A series of unsaturated polyesters based on the glycolyzed products, maleic anhydride and styrene, were prepared. Molecular weights and curing behavior of these polyesters were determined. Polymer concrete (PC) and polymer mortars (PM) made with these resins were investigated for their compressive strength. It has been found that the properties of PC and PM obtained from resins based on recycled PET are comparable to PC and PM made from virgin materials.
Electrochemical study of the nitroxyl radical derivatives built in the π‐conjugated poly(phenylenevinylene) skeleton
Authors: Toriu Shuichi , Kaneko Takashi , Nishide Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractThe electrochemical oxidation and reduction of the stable neutral nitroxyl radical gave the oxoaminium salt and hydroxylamine or nitroxyl anion, respectively. The electrochemical behavior of the N‐butylnitroxyl radicals or N‐butylhydroxylamines built in to various phenylenevinylene species were discussed in connection with its developed π‐conjugated structure based on cyclic voltammetric measurements. The aromatic nitroxyl radical showed two pairs of oxidation–reduction waves, but the acidic proton (hydroxylamine) changed its cathodic peak to a broad one with a shift to the anodic side. The π‐conjugated poly(phenylenevinylene) backbone and mobile proton of the hydroxylamine unstabilized the nitroxyl radical by retaining the energy gap.
Chitin–cellulose blends: phase properties in dimethylacetamide–LiCl
Authors: Bianchi E. , Marsano E. , Baldini M. , Conio G. , Tealdi A. 
Published: April 2003

AbstractChitin–cellulose blends dissolved in dimethylacetamide containing LiCl (7% w/w) have been studied in a wide concentration range, from very dilute solutions to medium concentrations and up to solid films (absence of diluent).The intrinsic viscosities at various chitin–cellulose ratios, as well as the phase diagram behavior, imply a good compatibility between the components. The result is confirmed by the infrared measurements on solid films. The lack of anisotropic phase formation in chitin–diluent binary solutions and the anomalous trend of v′CH–CE line on the phase diagram are both interpreted on the basis of aggregation phenomena.
Characterization of low‐density polybutadiene latexes by sedimentation field–flow fractionation
Authors: Blanda Marco , Reschiglian Pierluigi , Dondi Francesco , Beckett Ronald 
Published: April 2003

AbstractA procedure based on sedimentation field–flow fractionation for physical characterization of polydisperse latexes is presented. The particle density, dimensions, polydispersity, size distribution and aggregation can be determined for both narrow and wide polydispersities. The procedure is applied to the sample case of polybutadiene latexes with density lower than water. The results are compared with independent measurements obtained by electron microscopy. The relevance of significant steps of the procedure, such as the nonequilibrium corrections, are discussed.
Liquid crystalline poly(enamine ketone)s formed through hydrogen bonding
Authors: Yandrasits Michael A. , Zhang Anqiu , Bruno Katie , Yoon Yeocheol , Sridhar Krishnamurthy , Chuang Yuhway , Harris Frank W. , Cheng Stephen Z. D. 
Published: April 2003

AbstractA series of poly(enamine ketone)s (PEAKs) which exhibit liquid crystalline phases has been synthesized. The enamine ketone groups are able to exist in the cis and trans conformations. Molecular modelling results show that the cis conformation is energetically more favorable due to intramolecular hydrogen bonding. Model compound studies indicate that the formation of the mesogen requires the cis conformation in the enamine ketones to stabilize the liquid crystalline phase. This liquid crystalline phase is nematic for the model compound and the polymers. The heats of liquid crystal transition in the model compound and in PEAKs are very close (4.7 kJ/mol in model compound and 4.0 kJ/mol of repeating units in polymers). This is not only an indication of a similar percentage of the cis conformation in both cases, but also an example that the flexible ethyleneoxy spacers in the polymers do not contribute to the orientational order of this liquid crystalline phase. PEAKs can crystallize through either quenching from the isotropic melt or from the liquid crystalline phase. Crystallization kinetics exhibit the effect of pre‐ordering when these two different kinetics are compared.