bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and characterisation of poly(arylene sulfide)s, 5. Model compound studies of debromination reactions which occur during the synthesis of poly(arylene sulfide)s from copper(I) 4‐bromobenzenethiolates [copper(I) 4‐bromothiophenoxides]
Authors: Lovell Peter A. , Still Richard H. 
Published: April 2003

AbstractDebromination side‐reactions which occur during the synthesis of poly(arylene sulfide)s from copper(I) 4‐bromothiophenoxidesSystematic name: Copper(I) 4‐bromobenzenethiolates.
were investigated using bromobenzene as a model for the end unit in a poly(1,4‐phenylene sulfide) chain. Model reactions were conducted in quinoline, pyridine, and 10:1 (v/v) quinoline/pyridine solution in the presence and absence of copper(I) bromide, the condensation product of polymerisation. Reaction liquors were subjected to GLC and MS analysis and evidence is presented which indicates that a copper(I) initiated debromination reaction occurs yielding monophenylquinolines. A mechanism is proposed for the reaction and critically discussed. The consequences of the reaction at the macromolecular level are also described.
Measurement of conversion in free radical copolymerization from dilatometric data
Authors: Braun Dietrich , Cei Gustavo 
Published: April 2003

AbstractIn order to evaluate copolymerization rates from dilatometric measurements, the relationship between volume contraction and conversion (dilatometric constant) must be investigated. This can be done gravimetrically or by means of density measurements. In cases where one of the monomers is not able to homopolymerize, both methods lead to different values. Equations necessary for this evaluation were derived and verified in the systems diethyl maleate‐methyl methacrylate and diethyl maleate‐styrene. In some cases, the dependence of the dilatometric constant on feed composition may be predicted taking into account the contributions to volume contraction of the different bond types present in the copolymer. An expression was derived for describing this dependence in cases where one of the monomers does not homopolymerize. Its validity for the system diethyl maleate‐styrene was experimentally verified.
Polymeric phospholipid analogues, 20. Synthesis and polymerization of 20‐(methacryloyloxy)icosyl 2‐(trimethylammonio)ethyl phosphate and 32‐(methacryloyloxy)dotriacontyl 2‐(trimethylammonio)ethyl phosphate
Authors: Furukawa Akio , Shoji Hajime , Nakaya Tadao , Imoto Minoru 
Published: April 2003

Abstract20‐(Methacryloyloxy)icosyl 2‐(trimethylammonio)ethyl phosphate (4a) and 32‐(methacryloyloxy)dotriacontyl 2‐(trimethylammonio)ethyl phosphate (4b) were prepared and characterized. These monomers were polymerized and the properties of the resultant polymers are described.
Cyclopolymerization, 13. Cyclocopolymerizations of maleic anhydride with 1,5‐hexadiene and 2,5‐dimethyl‐1,5‐hexadiene
Authors: Kodaira Toshiyuki , Nishioka Kohji 
Published: April 2003

AbstractCyclocopolymerizations of maleic anhydride (1) with 1,5‐hexadiene (2a) and 2,5‐dimethyl‐1,5‐hexadiene (2b) were compared with those of 1 with 1,4‐dienes which have been reported to yield highly cyclized polymers following a bimolecular alternating inter‐intramolecular mechanism. The mole ratio of monomeric units of 1 to those of the dienes in the copolymers was almost 2:1, though it changed slightly with the monomer composition in the feeds. Although the fundamental aspect of the copolymerization of 1 with 1,5‐dienes was found to be similar to that with 1,4‐dienes, the structures of the copolymers are different from those obtained with 1,4‐dienes in that not only pendant double bonds, but also other unsaturations were detected. The unsaturations were formed by combination of propagating radicals with the allyl radical, which is considered to be formed by hydrogen abstraction from the penultimate hexenyl group. A mechanism is proposed to explain the degree of cyclization and the copolymer composition.
X‐ray studies on phospholipid bilayers, 7. Structure determination of oriented films of L‐α‐dimyristoylphosphatidylethanolamine (DMPE)
Authors: Suwalsky Mario , Duk Leonora 
Published: April 2003

AbstractThe bilayer structure of the phospholipid L‐α‐dimyristoylphosphatidylethanolamine (DMPE) was determined by X‐ray diffraction fiber methods. This study was carried out on oriented films at different degrees of hydration at room temperature (about 19°C). DMPE molecules pack very closely with their two hydrocarbon chains almost fully extended and coplanar with their polar group, which lies perpendicular to the chains. It was found that the unit cell dimensions of DMPE did not vary appreciably between 0 and 86% relative humidity nor did its longest axis with an excess of water. The methods and techniques used to prepare the specimens and to solve the structure are described.
Effect of poly(ethylene glycol) on the photochemical immobilization of an enzyme in photocrosslinkable poly(vinyl alcohol)
Authors: Ichimura Kunihiro 
Published: April 2003

AbstractA novel method was applied to improve the activity of enzymes immobilized in photocrosslinked poly(vinyl alcohol). Whereas the addition of glycerol to photosensitive poly(vinyl alcohol), bearing a styrylpyridinium group, diminishes the rate of photocrosslinking as well as the mechanical strength of the insolubilized gel, no considerable decrease in the rate of photoreaction was observed when poly(vinyl alcohol) was mixed with poly(ethylene glycol). This difference is based on the phase separation of the two water‐soluble polymers, resulting in the formation of a porous structure of the photocrosslinked gel. Immobilization of invertase in the photocrosslinked gel in the presence of poly(ethylene glycol) changes the activity, because of the case of diffusion of the substrate into the porous matrix.
Liquid crystalline polymers containing heterocycloalkanediyl groups as mesogens, 1. Liquid crystalline polymethacrylates and polyacrylates containing 1,3‐dioxane‐2,5‐diyl groups as mesogens in the side chain
Authors: Hsu Chain Shu , Rodriguez‐Parada José M. , Percec Virgil 
Published: April 2003

AbstractPolymethacrylates and polyacrylates containing 4‐[5‐(4‐methoxyphenyl)‐1,3‐dioxan‐2‐yl]‐phenol moieties as mesogenic units and an aliphatic spacer containing eleven methylene units were synthesized. Their phase behavior was studied by differential scanning calorimetry and optical polarizing microscopy, and compared with the phase behavior of the corresponding polymethacrylates and polyacrylates containing 4′‐methoxy‐4‐biphenylol as mesogens. All polymers present smectic mesomorphism. The substituted 2,5‐diphenyl‐1,3‐dioxane mesogen resembles a terphenyl mesogen in which the internal phenyl ring is hydrogenated. Even so, when compared with polymers containing biphenyl moieties, the glass transition temperatures of the polymers containing 1,3‐dioxane moieties are lower, although their isotropization occurs at higher temperatures.
Preparation of polyamides having 1,2,4‐triazine rings in the main chain
Authors: Akutsu Fumihiko , Suzuki Atushi , Saitoh Futoshi , Naruchi Kiyoshi , Miura Masatoshi , Nagakubo Kuniharu 
Published: April 2003

AbstractPolyamides having 1,2,4‐triazine rings in the main chain (6 and 7) were prepared from 3‐substituted 4,4′‐(1,2,4‐triazine‐5,6‐diyl)dibenzoic acids (5) and aromatic diamines. The thermal stability and the solubility of polyamides 6 and 7 were compared with those of structurally identical polyamides (polymers 3 and 4) obtained by polymer homologous reaction of polyamides having α‐diketone moieties with amidrazones. The effects of introduction of 1,2,4‐triazine‐5,6‐diyl unit in the main chain on the thermal stability and solubility of the polymers are discussed.
Solution properties of drug carriers based on poly[N‐(2‐hydroxypropyl)methacrylamide] containing biodegradable bonds
Authors: Ulbrich Karel , Koňák Čestmír , Tuzar Zdeněk , Kopeček Jindřich 
Published: April 2003

AbstractThe solution properties of water‐soluble drug carriers based on copolymers of N‐(2‐hydroxypropyl)methacrylamide containing p‐nitroaniline (drug model) attached to the copolymer by enzymatically degradable oligopeptide chains, were studied using light scattering, GPC and sedimentation methods. It was found that these polymers associate in water forming micelles with p‐nitroaniline being inside and hydrophilic polymer chains outside. The association number and compactness of micelles both depend on the content of hydrophobic side chains, polymer concentration and temperature. Micellar shells hinder the penetration of enzymes into the micellar core, thus reducing the rate of enzyme‐catalyzed release of p‐nitroaniline.
New polymer syntheses, 17. Cis/trans isomerism of 1,4‐cyclohexanedicarboxylic acid in crystalline, liquid‐crystalline and amorphous polyesters
Authors: Kricheldorf Hans. R. , Schwarz Gert 
Published: April 2003

AbstractDimethyl 1,4‐cyclohexanedicarboxylate was treated with various potential isomerization catalysts under reflux (ca. 280°C). Lithium cloride and sulfonic acids caused rapid isomerization. Also the diphenyl ester and 1,4‐cyclohexandicarbonyl dichloride were isomerized, and in all cases a thermodynamically controlled equilibrium with 66 ± 2% trans‐isomer was obtained. The same cis/trans ratio was found for the molten polyesters prepared from 1,4‐butanediole, 1,6‐hexanediole or phenylhydroquinone and 1,4‐cyclohexanedicarboxylic acid. The polyester, prepared at 20°C from phenylhydroquinone and trans‐1,4‐cyclohexanedicarbonyl dichlorid, exhibits a mesogenic phase above 250°C; yet, this LC‐phase is thermodynamically unstable and isomerizes to an isotropic melt containing 66 ± 2% trans‐isomer. However, when the free diacid or the crystalline polyester from hydroquinone and 1,4‐cyclohexanedicarboxylic acid are heated or synthesized at ca. 300°C, a content of 100% trans‐isomer is the thermodynamical optimum. This is also true for the LC‐phase of polyesters prepared from methyl‐ or chlorophydroquinone. The trans content of LC‐copolyesters, containing variable mole ratios of monomeric units of hydroquinone and phenylhydroquinone, varies with these mole ratios between 66 and 100%. Obviously, the coexistence of LC‐domains containing 100% trans‐isomer and isotropic domains containing 66% trans‐isomer are responsible for this result.
Structural study of compounds modelling elementary polymer units, 3. Molecular and crystal structure of 1,3,5‐tris[4′‐(C‐o‐carboranyl)biphenyl‐4‐yl]benzene
Authors: Lindeman Sergey V. , Struchkov Yurii T. , Shklover Valerii E. , Khotina Irina A. , Teplyakov Mikhail M. , Korshak Vasilii V. 
Published: April 2003

AbstractFollowing the studies on elucidating the main structural features of elementary units of polyphenylene‐type polymers prepared by condensation of di‐ and monoacetylaromatic compounds, an X‐ray structural analysis of 1,3,5‐tris[4′‐(C‐o‐carboranyl)biphenyl‐4‐yl]benzene (2) (systematic name: 1,3,5‐tris[)1,2‐dicarba‐closo‐dodecarborane(12)‐1‐yl(biphenyl‐4‐yl]benzene), which is the low‐molecular‐weight analog of one of the polymers in the given series, was performed. Compound 2 crystallizes as unstable solvate 1:1:1 with chloroform and benzene. The crystals are monoclinic, a = 17,060 Å, b = 20,220 Å, c = 18,448 Å, β = 102,79°, space group P21/n, Z = 4. Molecule 2 exhibits asymmetric conformation with substantial distortions of the linear geometry of polyphenylene units. The crystal is built of layers of molecules 2, the solvate molecules being situated between these molecules in the channels and cavities with a population of 2/3. The benzene molecules participate in stacking‐interaction with one of the carboranyl‐substituted (i.e., the strongest electron‐acceptor) benzene rings of the host molecule 2; chloroform molecules pack the channels without a specific interaction with the host molecules.
Thermotropic poly[oxy(2,6‐dimethyl‐1,4‐phenylene)]‐block‐poly(oxyterephthaloyloxy‐1,4‐phenylenealkylene‐1,4‐phenylene)
Authors: Fradet Alain , Heitz Walter 
Published: April 2003

AbstractBlock copolymers containing a rigid [oxy(2,6‐dimethyl‐1,4‐phenylene)] block and thermotropic poly[oxyterephthaloyloxy‐1,4‐phenylene‐hexamethylene (or/and decamethylene)‐1,4‐phenylene] blocks were synthesized. Their structures were examined by means of 1H and 13C NMR and X‐ray diffraction, and their liquid crystalline properties investigated by polarizing microscopy.
Relative affinities of mono and difunctional sulfoxides for lithium picrate in toluene. Effects of structure and stereochemistry
Authors: Buese Mark A. , Hogen‐Esch Thieo E. , Xu Wen‐Ying , Smid Johannes 
Published: April 2003

AbstractThe relative affinity of various mono and difunctional sulfoxides for lithium picrate in toluene was investigated by a competition method utilizing immobilized linear polyethers (glymes). In general, the difunctional sulfoxides were found to bind more strongly than the monofunctional sulfoxides. However, difunctional ligands which would result in eight‐membered ring chelated structures bound lithium ion more strongly than those which would result in six‐membered ring chelated structures.
Cellulose and chitosan hydrogen phthalates
Authors: Levesque Guy , Chiron Gérard , Roux Odette 
Published: April 2003

AbstractCellulose and chitosan hydrogen phthalates of various degrees of substitution were readily prepared from polysaccharides when reacted with phthalic, nitrophthalic and trimellitic anhydrides in presence of 4‐dimethylaminopyridine in dimethyl sulfoxide/triethylamine as reaction medium. Cellulose requires at least one equivalent of phthalic anhydride to dissolve entirely.
Adsorption of propylene and allene on TiCl3·1/3 AlCl3 and polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl
Authors: Kratochvíla Jan , Mejzlík Jiří 
Published: April 2003

AbstractAdsorption of propylene and allene from the gas phase on TiCl3·1/3 AlCl3 and TiCl3·1/3 AlCl3/AlEt2Cl catalyst was measured volumetrically. In the ranges of 296–334 K and 1–100 kPa, the adsorbed amounts of both gases was found to be approximately proportional to the gas pressure. The adsorbed amount of allene is about twice as high as that of propylene under the same conditions. Low heats of adsorption of both propylene and allene support the assumption of the physical nature of the adsorption. Addition of AlEt2Cl to the TiCl3·1/3 AlCl3 catalyst did not change substantially the sorption properties of the catalyst. Polymerization of allene with the system TiCl3·1/3 AlCl3/AlEt2Cl in heptane was found to be first order in monomer and the rate decreases with increasing yield. A mechanism of retardation by the polymer formed is probably operative. Both heptane‐soluble and heptane‐insoluble polyallenes are produced. The soluble polymer has M̄n ≈ 103 and a very narrow molecular weight distribution (M̄w/M̄n = 1,2 ± 0,2). Polyallene comprises mainly vinylidene units.
Polymerization beyond the gel point, 2. A study of the soluble fraction as a function of the extent of reaction
Authors: Argyropoulos Dimitris S. , Berry Richard M. , Bolker Henry I. 
Published: April 2003

AbstractTheoretical expressions that relate the amount of soluble material coexisting with the gel as a function of the extent of reaction beyond the gel point are tested experimentally. Three chemically different monomer combinations are examined for their yield of soluble material at various degrees of polymerization. It is concluded that, for the copolymerization of 1,3,5‐benzenetriacetic acid with 1,10‐decanediol, both modern and classical expressions adequately describe the experimental results beyond the gel point. The validity of the available equations is thus substantiated.
Polymere Aminoschutzgruppen. Synthese von neuen poly[2‐(N‐vinylpyridinio)ethoxycarbonyl]‐,2‐(N‐pyridinio)ethoxycarbonyl‐ und 2‐(N‐4‐picolinio)ethoxycarbonyl‐geschützten Aminoderivaten und kinetische Untersuchungen zur basisch induzierten Aminosäurefreisetzung
Authors: Ritter Helmut , Thöne Jochen 
Published: April 2003

Abstract2‐Bromoethoxycarbonyl modified amino acids were reacted with pyridine, 4‐picoline and poly(4‐vinylpyridine) to yield the corresponding 2‐(N‐pyridinio)ethoxycarbonyl derivatives as water‐soluble amino‐protecting groups. The kinetics and activation energies of basicly induced cleavage of the amino acids were investigated by 1H NMR spectroscopy in a D2O/NaOD medium. The polymeric salts were found to be more reactive than the low molecular weight pyridinium bromides because of electrostatic polymeric effects. Additionally, the kinetic measurements confirmed a E1cB mechanism for the cleavage of the urethane function. The formation of peptide bonds was performed in the case of poly[2‐(N‐4‐vinylpyridinioethoxycarbonyl)]‐protected amino acids in aqueous medium by water‐soluble carbodiimides.
Photochemical reaction of a polymer containing vinyl ether moieties with thiol compounds
Authors: Nishikubo Tadatomi , Shimokawa Tsutomu , Arita Hiroki 
Published: April 2003

AbstractThe photochemical addition reaction of poly(oxy‐1‐methyleneethylene‐co‐oxy‐1‐chloromethylethylene) (1), a polymer containing vinyl ether groups and synthesized by partial elimination reaction of poly(epichlorohydrin)Poly(oxy‐1‐chloromethylethylene).
, with methyl 3‐mercaptopropionate was carried out using benzophenone (BP) as a photosensitizer. The addition reaction proceeds with high conversion in benzene, toluene and tetrahydrofuran (THF). However, the degree of addition in both 1,4‐dioxane and N‐methyl‐2‐pyrrolidone (NMP) is relatively low, and the reaction does not proceed in dimethyl sulfoxide (DMSO) under the same reaction conditions. An optically active polymer containing pendant amino acid moieties was also synthesized by the photochemical reaction of polymer 1 with N‐acetyl‐L‐cysteine using BP as a photosensitizer in THF. It was found that the specific angle of rotation of the obtained polymer increases with increasing degree of conversion.
Synthesis and polymerization of poly(ethylene glycol) fumarates
Authors: Berlinova Iliyana V. , Panayotov Ivan M. 
Published: April 2003

AbstractFumaric esters of poly(ethylene glycol) (1a–d) were prepared as macromonomers. The halfesters 1a and 1c were obtained by interaction of maleic anhydride with the monoethers of poly(ethylene glycol) (2a and 2b) in the presence of 4‐dimethylaminopyridine, and the diesters 1b and 1d by esterification of methyl hydrogen fumarate (13) with the monoethers of poly(ethylene glycol) (2a and 2b). The macromonomers were found to homopolymerize and to copolymerize with styrene and methyl methacrylate following a radical polymerization mechanism.
Comparison of molecular weight distributions of polymers determined by dynamic light scattering
Authors: Witkowski Konrad , Woliński Leszek 
Published: April 2003

AbstractSeveral methods for the treatment of experimental data (including 3 different parameter‐fitting procedures, histograms, and Provencher's constrained regularization) are considered which allow to obtain molecular weight distributions w(M) from quasielastic light scattering measurements. As a result of the introduction of a few improvements to these methods described in the literature, we were able to use more severe criteria for the quality of the distribution functions obtained, based on the mean‐square deviation rather than on the coincidence of a few first moments. The quality of five investigated inversion methods was compared on the basis of simulated and experimental data for flexible chain polymers (polystyrene standards) in dilute solution.
Polymerization of tetrahydrofuran, 2. Equilibrium monomer concentration
Authors: Hirota Masahiro , Fukuda Hiroyuki 
Published: April 2003

AbstractThe equilibrium polymerization of tetrahydrofuran was studied at relatively low initial monomer concentrations with 1‐methyltetrahydrofurylium hexachloroantimonate as initiator. The equilibrium concentrations of monomer, [M]e, and initiator, [I]e, as well as the equilibrium number‐average degree of polymerization, Pn, were determined by means of 1H NMR spectroscopy, and found to follow simplified relations, which were derived from Tobolsky's equations.
Kinetik der startreaktion der radikalischen homo‐ und copolymerisation von styrol, N‐vinyl‐2‐pyrrolidon und methylmethacrylat
Authors: Braun Dietrich , Czerwinski Wojciech K. 
Published: April 2003

AbstractIn one, two and three component polymerizations of the monomer system styrene (St = M1), N‐vinyl‐2‐pyrrolidone (NVP = M2) and methyl methacrylate (MMA = M3) the rate constants of the initiation step 2kdf were measured in bulk at 60°C by means of the inhibition method with the stable Banfield radical as inhibitor and AIBN as initiator. The obtained 2kdf‐values depend non‐linearly on the monomer feed. It results from the evaluation of initiator decomposition constant kd that the chain initiation step is mainly determined by the rate of initiator decomposition. In all polymerizations the efficiency factor f was almost equal to 0,5.
Evidence of crosslinks in a butadiene‐divinylbenzene‐ethylvinylbenzene copolymer by metathesis degradation
Authors: Hubmann Ewald , Loy Walter A. , Pongratz Thomas , Hummel Klaus 
Published: April 2003

Abstract1,3‐Butadiene was copolymerized with a mixture of divinylbenzene isomers containing ethyl‐vinylbenzene isomers. The crosslinked copolymers were degraded in a cross metathesis reaction with (Z)‐2‐butene or (E)‐3‐hexene using the catalyst WCl6/Sn(CH3)4. The low‐molecular‐weight products were investigated by gas chromatography/mass spectrometry coupling. Products containing the crosslinks were found. Others were attributable to copolymer units resulting from butadiene and ethylvinylbenzene. Characteristic mass spectra of the products are discussed.
Synthesis and properties of star shaped block copolymers of styrene and ethylene oxide
Authors: Xie Hongquan , Xia Jun 
Published: April 2003

AbstractStar shaped block copolymers with two arms of polystyrene (PS) blocks and two arms of poly(oxyethylene) (PEO) blocks were synthesized by coupling living PS anions first and then living PEO anions, using SiCl4 as the coupling agent, while the star shaped block copolymers with two arms of PS blocks and one arm of PEO block were prepared by using CH3SiCl3 as the coupling agent. The products were purified by extractions, and the purified copolymers were characterized by GPC, IR, 1H NMR and torsional braid analysis. The crystalline, emulsifying and complexing properties and also the phase transfer catalytic effect of the star shaped block copolymers were studied.
Linear polymerization of endo‐dicyclopentadiene initiated by metathesis catalysts
Authors: Pacreau Annie , Fontanille Michel 
Published: April 2003

AbstractThe polymerization of endo‐dicyclopentadieneSystematic name of endo‐dicyclopentadiene is: tricyclo[5.2.1.02,6]deca‐3,8‐diene.
(endo‐DCP) by the metathesis catalyst ReCl5/(CH3)4 Sn gave a substantial yield of a linear polymer with high molecular weight and high content of cis double bonds. The kinetics of the early stage of the reaction was studied by calorimetry. The polymerization proceeds via an oligomerization reaction followed by the formation of polymers. A mechanistic scheme is proposed to explain the generation of the primary active species and the two‐step polymerization process.