bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epitaxial crystallization of trans‐1,4‐polybutadiene on highly oriented isotactic poly(propylene) films
Authors: Petermann Jürgen , Xu Yang , Loos Joachim , Yang Decai 
Published: April 2003

AbstractEpitaxial crystallization of trans‐1,4‐polybutadiene (PBD) on highly oriented isotactic poly(propylene) (iPP) has been investigated at different crystallization temperatures and rates. From electron microscopy and electron diffraction, it is confirmed that epitactic growth of the low‐temperature modification (monoclinic) with microcrystals of PBD on the iPP films takes place with their chain directions about ±50° apart. No epitaxial relationship occurs between the high‐temperature modification (hexagonal) of PBD and the iPP substrate. Thermal analyses of PBD‐PP layered films indicate that the epitaxy has an important effect on the formation of the high‐temperature modification of PBD.
Microstructure of styrene‐methacrylic acid and styrene‐acrylic acid copolymers, 5 UV absorption study of styrene‐methacrylic acid and styreneacrylic acid copolymers
Authors: S̀witata‐Żeliazkow Maria 
Published: April 2003

AbstractUV absorption spectra of styrene‐methacrylic acid and styrene‐acrylic acid copolymers prepared in benzene solution and in emulsion were investigated. They were compared to UV spectra of derived copolymers prepared by methylation of the carboxyl groups of the parent copolymers. In the spectra of the methylated copolymers only a hypochromic effect on all peaks was observed, whereas in the spectra of the parent acid copolymers hypochromic as well as hyperchromic effects were found. They depend on the kind of acid, its content in the copolymer and on the type of the copolymer. These differences may be explained on the basis of hydrogen bonds formed between the π‐electrons of phenyl rings and carboxyl groups. It seems that the most sensitive peak to these hydrogen bonds is that at 259 nm, while the peak at 269 nm is sensitive to electronic interactions between adjacent monomeric units.
Preparation and dielectric properties of cellulose derivatives with high‐polarity substituents
Authors: Sato Takaya , Tsujii Yoshinobu , Minoda Masahiko , Kita Yasuo , Miyamoto Takeaki 
Published: April 2003

AbstractAn attempt was made to prepare highly dielectric polymers from O‐(2,3‐dihydroxypropyl)‐cellulose (DHPC)The structure of O‐(2,3‐dihydroxypropyl)cellulose (Fig. 1) is different from other cellulose derivatives such as methylcellulose or cellulose acetate, since the substituents can be oligo(dihydroxypropyl)s with different chain lengths (n ≥ 1). The chemical structure of DHPC is defined by the number of hydroxyl groups substituted per anhydroglucose unit, i. e., degree of substitution (DS), and the number of combined glycidol groups per anhydroglucose unit, i. e., molar substitution (MS).
by cyanoethylation, nitrobenzoylation, cyanobenzoylation, and trifluoroacetylation. To accomplish this, DHPC samples with different molar substitution (MS) were prepared by homogeneous dihyroxypropylation of cellulose with glycidol in a 10 wt.‐% LiCl/DMA solvent system. Among the sample derivatives, all of which are soluble in various organic solvents, the cyanoethylated derivatives with high MS values have dielectric constants higher than 30 at room temperature and 1 kHz. These derivatives also form cholesteric liquid‐crystalline (LC) phases in a wide temperature range, but the dielectric constant is independent of the phase structure. The results are discussed in terms of the structural difference among the sample polymers.
Hydrogenation of liquid carboxylated nitrile rubber
Authors: Bhattacharjee Susmita , Bhowmick Anil K. , Avasthi B. N. 
Published: April 2003

AbstractHydrogenation of liquid carboxylated nitrile rubber (L‐XNBR) was carried out using homogeneous palladium and rhodium catalysts. It was observed that the six‐membered cyclic palladate complex of 2‐benzoylpyridine, 1, reduces the carbon‐carbon double bonds without affecting the nitrile and carboxyl functionality. The intrinsic viscosity of the polymers remains unchanged during hydrogenation. The glass transition temperature is marginally lowered for the hydrogenated products. A great extent of decarboxylation was obtained for samples hydrogenated in presence of the rhodium complex, 2.
Cis‐trans isomerization of polyesters based on 1,4‐cyclohexanedicarboxylic acid in the liquid‐crystalline and isotropic states
Authors: Tenkovtsev Andrey V. , Rutman Alla B. , Bilibin Alexander Yu. 
Published: April 2003

AbstractPolyesters based on 4,4′‐(cis‐1,4‐cyclohexanedicarbonyldioxy)dibenzoic acid and resorcinol or chlorohydroquinone were synthesized. The rate constants of the cis/trans isomerization reaction in the liquid‐crystalline and isotropic states were measured. A liquid‐crystalline environment is shown to enhance the rate of isomerization, but the chain rigidity determines the cis/trans equilibrium ratio of 1,4‐cyclohexanedicarboxylic acid moieties.
Thermal behaviour of highly stereoregular syndiotactic polypropene from homogeneous catalysts
Authors: Balbontin Giulio , Dainelli Dario , Galimberti Maurizio , Paganetto Guglielmo 
Published: April 2003

AbstractThermal characterization was carried out on highly stereoregular and regioregular syndiotactic polypropene (sPP) obtained with isopropylidene(cyclopentadienyl)(9‐fluorenyl)zirconium dichloride and methylaluminoxane. The influence of molecular weight and syndiotacticity degree on the thermodynamic melting point (T°m) of sPP were separately investigated by examining samples with a fully syndiotactic pentads content (rrrr) ranging from ca. 81% to ca. 94% and with an weight‐average molecular weight (M̄w) ranging from 9,6 · 104 to 17,3 · 104. Upon excluding any influence of the molecular weight, the correlation between the rrrr pentads content and the T°m of the samples led to the extrapolation of the thermodynamic melting point for a fully syndiotactic polypropene.
Synthesis of side‐chain liquid‐crystalline polyethers by chemical modification of polyepichlorohydrin
Authors: Piercourt Stéphane , Lacoudre Nelly , Borgne Alain Le , Spassky Nicolas , Friedrich Claude , Noël Claudine 
Published: April 2003

AbstractCopolymers derived from polyepichlorohydrin (PECH), bearing pendant mesogenic units are obtained by chemical modification of atactic samples of PECH with sodium 4‐cyano‐4′‐biphenoxide. Rate and yield of substitution are strongly dependent on the molecular weight of the used PECH. A substantial rise (ΔT ∼ 110°C) of glass transition temperature with the percentage of incorporated cyanobiphenyl groups is observed. Copolymers with an amount of substitution higher than 60% present thermotropic liquid‐crystalline behaviour and form nematic phases. Chemical modification of PECH offers a simple method for the synthesis of new liquid‐crystalline polyethers whose transition temperatures can be adjusted by varying the amount of substitution.
Dynamics of the evolution of volatile products during laser‐induced polymer destruction
Authors: Kalontarov Lev I. , Marupov Rakhim , Bekmukhamedov Anvar T. 
Published: April 2003

AbstractThe dynamics of evolution of volatile products arising during destruction of poly(vinyl alcohol) and polyacrylnitrile films under the action of cw laser radiation were investigated by means of time‐of‐flight mass spectrometry. It was found that the evolution of volatiles occurs in two stages, one isothermal and the other nonisothermal. Depending on laser focusing and power, the nonisothermal stage comprises three dynamic regimes of desorption of volatile products: regime of single ejection, oscillating regime and chaotic behaviour of evolution. It is shown that the various regimes of desorption are due to inhomogeneity of laser heating and nonuniform propagation of the destruction wave from the centre of the laser beam to the periphery.
Synthesis of electrically conductive polypyrrole films by interphase oxidative polymerization
Authors: Nakata Masakazu , Shiraishi Yohtarou , Taga Megumi , Kise Hideo 
Published: April 2003

AbstractPolypyrrole (PPy) films were synthesized by interface polymerization reactions between aqueous solutions of FeCl3 and solutions of pyrrole monomer in organic solvents. The polymerizations were studied using various organic solvents, and flexible and uniform PPy films were obtained using benzene or toluene as solvents. It was found that polymerization time and organic solvents strongly affect the thickness and conductivity of the films, but the atomic composition of the PPy films was independent of the reaction conditions. The mechanism of the film growth at the interface is discussed on the basis of film properties and the observation of the film surface using scanning electron microscopy.
Elementarprozesse der ziegler‐katalyse, 5. Lösungsmitteleinflüsse am Beispiel stereorigider Zirkonocen/methylaluminoxan Ziegler‐Katalysatoren
Authors: Herfert Norbert , Fink Gerhard 
Published: April 2003

AbstractThe syndiotactic propene polymerization was investigated by means of the Cs‐symmetric isopropylidene(fluorenyl)(cyclopentadienyl)zirconium dichloride/methylaluminoxane (iPr(Flu)‐(Cp)ZrCI2/MAO) catalyst system in toluene/methylene chloride solvent mixtures. The main result is that with increasing dielectric constant of the solvent mixture the polymerization rate increases linearly but the stereospecificity of the catalyst decreases strongly; this is revealed through a drastic decay of the rrrr‐pentads and of the melting point of the polymers. Hence, the stereospecificity of this catalyst system is connected with the existence of a polarized Zr‐CI‐AI‐complex (in toluene) or at least of a tight contact ion pair with a stereoregulating role of the counter ion. The loss of the stereospecifity in polar solvents is caused by an isomerization reaction of the solvent‐separated free zirconocene species via migration of the growing polymer chain before the next monomer insertion. But in the case of the isotactic catalyst system dimethyl‐silyl(bisindenyl)zirconium dichloride/methylaluminoxane (Me2Si(Ind)2ZrCl2/MAO) with a C2‐symmetric π‐ligand system the migration of the growing polymer chain in polar solvents causes no isomerization.
Radikalisch polymerisierbare Gallensäuren in Monoschichten, Mizellen und Vesikeln
Authors: Ahlheim Markus , Hallensleben Manfred L. 
Published: April 2003

AbstractThe synthesis of radically polymerizable derivatives of cholic acid containing a methacrylic group directly attached to C3 or via a C11 cinnamic ester spacer is described. The monomers form monolayers, vesicles and micells. Both in vesicles and in micells the monomers do not undergo neither photodimerization via the cinnamoyl group nor do they polymerize, but they photodimerize in an amorphous film and polymerize in isotropic solution.
Cation exchange resins based on phosphonomethyl‐substituted phenols
Authors: Kaiser Jürgen , Schied Bernd , Trautmann Norbert , Vogt Walter 
Published: April 2003

AbstractPhosphonomethyl‐substituted phenols are readily obtained from o‐hydroxymethylated phenols and trialkyl phosphites. The free acids, incorporated into phenol‐formaldehyde resins, act as cation exchangers with remarkable selectivity for different metal ions.
Copolymerization of olefins with Kaminsky‐Sinn‐type catalysts
Authors: Uozumi Toshiya , Soga Kazuo 
Published: April 2003

AbstractCopolymerizations of ethylene with propene, ethylene with 1‐hexene and propene with 1‐hexene were performed at 40°C under atmospheric using three kinds of Kaminsky‐Sinn‐type catalysts which differ in stereospecificity: Cp2ZrCl2‐methylaluminoxane (MAO) (aspecific); Et[IndH4]2 ZrCl2‐MAO (isopecific); i‐Pr(Cp)(Flu)ZrCl2‐MAO (syndiospecific).The 13C NMR analysis of copolymers showed that the incorporation of higher olefins decreases in the following order: i ‐Pr(Cp)(Flu)ZrCl2‐MAO > Et[IndH4]2ZrCl2‐MAO > Cp2ZrCl2‐MAO, and that stereospecificity is retained even in the copolymerization.The product of monomer reactivity ratios (r1 · r2) indicates that poly(propene‐co‐1‐hexene) is a statistically random copolymer whereas both poly(ethylene‐co‐propene) and poly(ethylene‐co‐1‐hexene) have somewhat alternating character regardless of catalyst stereospecificity.
Structural study of the aging and thermal evolution of polyiodide chains in doped trans‐polyacetylene
Authors: Albouy Pierre‐Antoine , Pouget Jean‐Paul , Halim John , Enkelmann Volker , Wegner Gerhard 
Published: April 2003

AbstractThe evolution of the structure of iodine chains in iodine‐doped polyacetylene has been followed as a function of temperature. It is shown that these chains exhibit a disorder of the second kind characterized by the lack of long‐range order in chain direction. A low‐temperature improvement of intra‐chain order demonstrates that a substantial part of this disorder is thermal in nature. A parallel is drawn to similar effects frequently observed in crystalline iodine chain organic charge transfer salts. Furthermore, fresh samples with a nominal composition CHI0,24 are unstable under the X‐ray beam. They exhibit a slow transition toward an apparently stable form corresponding to CHI0,19. The diffraction pattern in chain direction of this form can be quantitatively explained with a simple model using triiodide chains only. A comparison with other models proposed in the literature is made.
Ethylene polymerization on a high activity supported catalyst: MgCl2 (THF)2/TiCl4/AlEt2Cl
Authors: Nowakowska Maria , Bosowska Kornelia 
Published: April 2003

AbstractA magnesium/electron donor complex was used as support for the synthesis of a titanium catalyst. By interaction of TiCl4 with MgCl2(THF)2 a highly active and stable catalyst for ethylene polymerization was obtained. The catalytic activity of the MgCl2(THF)2/TiCl4/AlEt2Cl system in the polymerization of ethylene was investigated as a function of Mg/Ti and Al/Ti mole ratios as well as the donor concentration in the system. Some kinetic studies of ethylene polymerization in the presence of this catalyst allowed us to determine the concentration of active centres (ca. 60 mol‐% of Ti), rate constants of elementary reactions (kp ≈ 92 dm3/(mol · s)) and kinetic equations. From these results it was possible to find further evidence for the role of the donor ligands in titanium catalysts supported on magnesium dichloride in the presence of Al‐alkyls as cocatalysts.
1‐Butene polymerization in the presence of MgCl2‐supported Ziegler‐Natta catalysts: polymer microstructure in relation to polymerization mechanism
Authors: Busico Vincenzo , Corradini Paolo , De Biasio Rosanna 
Published: April 2003

Abstract1‐Butene polymerization in the presence of MgCl2‐supported Ziegler‐Natta catalyst systems was investigated under conditions such as to obtain polymer samples containing high amounts of (prevailingly) syndiotactic sequences. These were found in part to be linked to (prevailingly) isotactic sequences in stereoblock macromolecules. More clearly than in the case of the corresponding propene polymers, the spectroscopic characterization of the poly(1‐butene) samples proved that the syndiospecificity in such systems is dictated by the asymmetry of the last inserted monomer unit.
A novel route to poly(triarylcarbinols)
Authors: Zolotukhin Mikhail G. , Akhmetzyanov Shamil S. , Shishlov Nikolai M. , Latchinov Alexey N. , Sultanova Venera S. , Spirikhin Leonid V. , Khalilov Leonard M. 
Published: April 2003

AbstractA novel scheme for a two‐stage synthesis of poly(triarylcarbino1)s is suggested. In the first stage, the homopolycondensation of 3‐(4‐biphenylyl)‐3‐chloro‐1,1 ‐dioxobenzo[c][1,2]‐oxathiolane (6a) via a Friedel‐Crafts reaction gives the polymeric arylene sulfophthalide 7. In the second stage, alkaline hydrolysis of the latter under mild conditions leads to linear, high‐molecular‐weight, film‐forming poly(triarylcarbino1) 8 containing sulfonate groups. The polymer films show photo‐ and thermochromism. The density of paramagnetic centres in 8 is < 1015 spins per gram, and increases on heating up to 1018 spins per gram, the initial value being restored after cooling and exposure to air.
Swelling behavior of hydrogels containing phosphate groups
Authors: Nakamae Katsuhiko , Miyata Takashi , Hoffman Allan S. 
Published: April 2003

AbstractHydrogels containing phosphate groups were prepared by copolymerization of 2‐methacryloyl‐oxyethyl dihydrogen phosphate (phosmer) and various hydrophilic monomers [N,N‐dimethyl‐acrylamide (DMAAm), acrylic acid (AAc) and 2‐hydroxyethyl methacrylate (HEMA)], and the swelling behavior was investigated. These hydrogels are thermo‐sensitive. Phosmer‐DMAAm and phosmer‐HEMA hydrogel deswell with increasing temperature, but for the phosmer‐AAc hydrogel the swelling ratio increases with temperature. Interestingly, the swelling ratio decreases with an increase in phosphate group content. This unusual behavior may arise from the phosphate group acting both as the functional group and the crosslinking agent.
Synthesis and thermotropic liquid‐crystalline properties of polyurethane‐polystyrene graft copolymers
Authors: Sato Moriyuki , Yanahara Masanobu , Kobayashi Takanori , Mukaida Ken‐ichi 
Published: April 2003

AbstractNew polyurethane‐graft‐polystyrenes (4) of well‐defined structures and compositions were synthesized by macromonomer technique and the structure‐liquid‐crystalline (LC) property relationship is discussed. The expected graft copolymers with polystyrene grafts were prepared by melt polycondensation of a mixture of a dihydroxy derivative of biphenyl as a mesogenic moiety (1) and a dihydroxy‐terminated styrene macromonomer (2) with diphenyl N,N′‐hexamethylenedi‐carbamate (3). Of the resulting polymers mesogenic unit‐rich graft copolymers retain the LC mesophases in spite of introduction of the polystyrene segments onto the polyurethane backbones and possess microphase‐separated structures. Polystyrene‐rich copolymers reveal no well‐defined LC mesophases and analogous thermal properties to the polystyrene segments.
Group transfer initiated polymerization of methyl methacrylate catalyzed by [((C6H5)3P)2N]+HF
Authors: Martin David T. , Bywater Stanley 
Published: April 2003

AbstractExperments are reported on the group transfer polymerization of methyl methacrylate using a new bifluoride salt, bis(triphenylphosphoranylidene)ammonium hydrogendifluorideCommonly abbreviated as PPN bifluoride (PPN HF2).
[((C6H5)3P)2N]+HF, as catalyst. Good molecular weight control was observed although a small deviation from the expected value was found. Side reactions of catalyst with initiator, and termination (cyclization) of the active centres at low monomer concentrations were investigated. The similarities between this method and classical anionic polymerization are discussed.
Synthesis of telechelic poly(p‐phenylene) derivatives
Authors: Kallitsis Joannis K. , Rehahn Matthias , Wegner Gerhard 
Published: April 2003

AbstractThe synthesis of oligo(2,5‐dialkyl‐p‐phenylene)s bearing terminal boronic acid, bromo‐,acetoxy‐, methoxycarbonyl‐ or carbonic acid groups is reported. Oligomers of number‐average degree of polymerization 6 ≤ Pn ≤ 20 were obtained by the palladium‐catalyzed coupling of aromatic halides with aromatic boronic acids. The same synthetic approach was used to prepare derivatives of p‐terphenyl, bearing hydroxy‐, acetoxy‐, carboxy‐ or amino‐groups in 4,4″‐position.
Synthesis and properties of polyesters derived from 2′,5′‐dialkyl‐p‐terphenyl‐4,4″‐diol
Authors: Kallitsis Joannis K. , Wegner Gerhard , Pakula Tadeusz 
Published: April 2003

AbstractA series of polyesters based on 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐diol as one component and various aliphatic or aromatic diacids as the second component have been synthesized. The polyesters are soluble and film forming. Materials based on the terphenyldiol and terephthalic acid or the terphenyldiol and 2′,5′‐dihexyl‐p‐terphenyl‐4,4″‐dicarboxylic acid show a temperature dependence of the elastic modulus between 100 and 300°C resembling the behavior of hard elastic polymers, Glass transition phenomena in the conventional sense were not observed. The materials exhibit good mechanical properties up to temperatures well above 300°C.
Concerning the reaction of zirconocene dichloride and methylalumoxane: Homogeneous Ziegler‐Natta catalytic system for olefin polymerization
Authors: Cam Darinn , Giannini Umberto 
Published: April 2003

AbstractThe interaction of zirconocene dichloride (Cp2ZrCl2) with methylalumoxane (MAO), the two components of homogeneous catalyst for olefin polymerization, was studied by 1H NMR spectroscopy. Its was found that Cp2ZrCl2 is monoalkylated by Al2(CH3)6 present in MAO. The trimethylaluminium contained in MAO appears to be the active species in the alkylation of the zirconocene dichloride. The Cp2ZrCH3Cl likely forms, with an excess of MAO, highly polarized species. These are decomposed by a complexing agent of MAO such as KCl.
Helical amylose complexes with organic complexands, 1. Microcalorimetric and circular dichroitic investigations
Authors: Wulff Günter , Kubik Stefan 
Published: April 2003

AbstractComplexation of different synthetic amyloses (Pn between 9 and 1000) with sodium dodecyl sulfate and 4‐tert‐butylphenol was investigated by means of microcalorimetry and circular dichroism. The results were compared with the complexation behaviour of α‐, β and γ‐cyclodextrins with the same guest molecules. All amyloses investigated formed complexes with sodium dodecyl sulfate in a fast reaction. In these complexes the amyloses possess a helical conformation with six glucose units per turn, which should already exist in aqueous solution before complexation. tert‐Butylphenol only forms complexes with amyloses of a Pn higher than 100. In this case apparently the amylose must adjust to complex the tert‐butylphenol in a helix with seven or eight glucose units per turn. Using these methods the complexation of sodium dodecyl sulfate with amylopectin was also demonstrated.
Cationic polymerization of 1,2‐epoxy‐3‐nitropropane in the presence of ethylene glycol, 3 Determination of the mechanism
Authors: Lagarde Florence , Reibel Leonard , Franta Emile 
Published: April 2003

AbstractCationic polymerization of 1,2‐epoxy‐3‐nitropropane was performed in the presence of ethylene glycol and borontrifluoride etherate under conditions meant to favor the Activated Monomer Mechanism. In two previous papers, we showed that the Activated Monomer Mechanism prevails until the number‐average molecular weight M̄n reaches a value of about 350. In this article, we show that beyond this value another mechanism competes effectively with the latter one: oxygen atoms of the oligomeric chains react with the protonated monomer leading to the formation of non‐cyclic tertiary oxonium ions. These ions may react with various nucleophiles during polymerization or upon deactivation, which explains the M̄n limitation as well as the excess of hydroxyl groups observed.