bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical behaviour of liquid‐crystalline polymers and their networks
Authors: Pakula Tadeusz , Zentel Rudolf
Published: April 2003

Liquid‐crystalline polymers with mesogenic groups in the main chain and side chains as well as their networks are studied by the dynamic mechanical method. The homopolymers are compared with chiral copolymers of a similar chemical structure. Mechanical relaxation transitions are correlated with transitions observed by differential scanning calorimetry. In the nematic phase a flow‐thinning effect has been observed both for uncrosslinked polymers and for crosslinked systems. A possible molecular interpretation of the observed mechanical behaviour is discussed.
Polymers from multifunctional isocyanates, 6. Thermotropic di‐ and oligo(urethane)s from novel triad diisocyanatodiesters
Authors: Mormann Werner , Benadda Saria
Published: April 2003

The first examples of triad diisocyanatodiesters with a substituent in the central aromatic ring, namely methyl‐, trimethyl‐, tert‐butyl‐, and phenyl‐substituted 1,4‐phenylene bis(4‐isocyanato‐benzoates), and bis(4‐isocyanatophenyl) trans‐1,4‐cyclohexanedicarboxylate are described. The diisocyanatodiesters melt in the range of 160°C, give nematic mesophases and have a clearing transition above 300°C except for the phenyl‐substituted diisocyanate which exhibits a monotropic mesophase. Due to the more favourable aspect ratio of the mesogens thermotropic diurethanes were obtained by reaction with butanol and oligomeric thermotropic polyurethanes resulted from the reaction with butanol and diethylene glycol, triethylene glycol, or 3‐methyl‐1,5‐pentanediol. The phase behaviour of the urethanes in relation to their structure is discussed. The thermal stability of the urethanes is limited by the occurrance of urethane cleavage.
Properties of poly[N‐2‐(methyacryloyloxy)ethyl‐N,N‐dimethyl‐N‐3‐sulfopropylammonium betaine] in dilute solution
Authors: Huglin Malcolm B. , Radwan Mostafa A.
Published: April 2003

Poly[N‐2‐(methacryloyloxy)ethyl‐N,N‐dimethyl‐N‐3‐sulfopropylammonium betaine] (1) which is an interesting polyzwitterion polymer by virtue of its “antipolyelectrolyte solution behaviour” has been prepared by free‐radical initiated polymerization in aqueous solution. Isothermal fractionation was conducted at 294 K employing formamide as solvent and acetone as precipitant. Twelve fractions covering a wide range of weight‐average molecular weight (215 000 ≤ M̄w ≤ 2 070 000) were used to characterise the polymer by light scattering, membrane osmometry and viscosity measurements. The Mark‐Houwink equations, established for 1 in two good solvents, 2,2,2‐trifluoroethanol (TFE) and 1,0 M aqueous NaCl solution, show that the polymer has a random coil configuration and that TFE is a thermodynamically better solvent than 1,0 M aqueous NaCl solution. The random coil configuration of 1 in TFE was confirmed from the dependence of the polymer dimensions on molecular weight.
Synthesis of poly(methyl methacrylate) macromonomers with phenolic functionality by group transfer polymerization and their use in polycondensation reactions
Authors: Heitz Thomas , Webster Owen W.
Published: April 2003

Methyl 1‐trimethylsiloxy‐2‐[2,5‐bis(trimethylsiloxy)phenyl]vinyl ether (6) was used as the initiator for the group transfer polymerization (GTP) of methyl methacrylate (MMA) to give macromonomers with aromatic hydroxyl functions. Quantitative removal of the silyl‐protective groups was achieved by acidic or fluoride‐catalyzed cleavage to give the deprotected macromonomer 9. The reactivity of this macromonomer in polycondensation reactions was shown by the synthesis of a liquid‐crystalline main‐chain polyester with poly(methyl methacrylate) (PMMA) side chains (PES‐graft‐PMMA) (15) and a 4,4′‐isopropylidenediphenol‐based polycarbonate (PC‐graft‐PMMA) (19).
Living cationic polymerization of isobutyl vinyl ether with hydrogen iodide/metal acetylacetonate as initiating system
Authors: Sawamoto Mitsuo , Kojima Kazushige , Higashimura Toshinobu
Published: April 2003

Living cationic polymerization of isobutyl vinyl ether (IBVE) was achieved with hydrogen iodide/metal acetylacetonate [HI/M(acac)n] as initiating systems at −40°C in toluene or dichloromethane; the suitable M(acac)n complexes turned out to include Zn(acac)2, Fe(acac)3, and Al(acac)3. Thus, the number‐average molecular weights (M̄n) of the polymers increased proportionally to the monomer conversion, were regulated by the feed ratio of monomer to hydrogen iodide ([M]0/[HI]0), and were in good agreement with the calculated values on the assumption that one living polymer per molecule of hydrogen iodide is formed, while the molecular‐weight distributions of the polymers remained fairly narrow (M̄w/M̄n ≤ 1,2). An increasing concentration of M(acac)n accelerated the polymerization but did not influence the M̄n of the living polymers, thus indicating that the metal acetylacetonates serve as activators for the growing end derived from hydrogen iodide. When Mg(acac)2, and Sn(acac)4 were employed as M(acac)n with hydrogen iodide, polymerization hardly occurred at −40°C in dichloromethane.
Nematic elastomers, 1. Effect of the spacer length on the mechanical coupling between network anisotropy and nematic order
Authors: Kaufhold Wolfgang , Finkelmann Heino , Brand Helmut R.
Published: April 2003

The influence of the spacer length was investigated for the correlation between the network anisotropy and the order parameter of the mesogenic units. Stress‐optical measurements show that a closer coupling of the mesogenic moieties to the polymer backbone results in an increased interaction between the mechanical field and the mesogenic groups. The correlation between the phase transformation temperature TNI and the mechanical stress σ is represented using both, our experimental measurements and the derivation from the Landau‐de Gennes (LDG) formulation. From our results, it is possible, for the first time, to estimate the cross‐coupling coefficient U between the order parameter and the strain of a nematic elastomer. The analysis of the elastic properties of the elastomers suggests that non‐linear coefficients might become important to obtain quantitative agreement between theory and experiment.
Modification of membrane surfaces by plasma deposition of thin fluorocarbon films without affecting bulk properties
Authors: Clarotti Giorgio , Aoumar Abdallah Ait Ben , Schué François , Sledz Joseph , Geckeler Kurt Ernst , Flösch Dietmar , Orsetti André
Published: April 2003

The deposition of films from an argon plasma containing a mixture of ethylene oxide or hydrogen and perfluorohexane was tried to obtain very hydrophobic, less hydrophobic and intermediate coatings. This paper studies more extensively the deposition of a thin coating from a perfluorohexane and hydrogen plasma on polysulfone and polyhydroxybutyrate membranes to optimize their surface properties without affecting their filtering properties. The plasma deposition of smooth and very hydrophobic fluorocarbon coatings seems to increase the bio‐ and hemocompatibility of poorly biocompatible membranes. The treated substrates were characterized by measuring the mass variations, surface profilometry and contact angle measurements, as well as scanning electron microscopy and electron spectroscopy for chemical analysis.
13C NMR analysis of α‐olefins copolymers with 1,3‐butadiene obtained with zirconocenes/methylalumoxane catalysts
Authors: Galimberti Maurizio , Albizzati Enrico , Abis Luigi , Bacchilega Giancarlo
Published: April 2003

Ethylene copolymers with propene and/or 1,3‐butadiene were obtained using bis(η5‐cyclopentadienyl)zirconium dichloride (1) or ethylenebis[1‐3a, 7a‐η‐(4,5,6,7‐tetrahydro)‐1‐indenyl]zirconium dichloride (2) and methylalumoxane as catalytic systems. A detailed 13C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3‐butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of α‐olefins. The presence of trans‐1,2‐cyclopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butadiene terpolymers. A different behaviour of the two catalysts was observed.
Synthesis and characterization of dextran radiocontrast carriers, 1. Ether methylamide derivatives
Authors: Paris Dominique , Meyer Dominique , Nigretto Jean Maxime
Published: April 2003

The synthesis of dextran radiocontrast carriers was undertaken to obtain derivatives expected to have slow and controlled biodegradation as well as slow extravascular diffusion features. The results presented here particularly concern derivatives including a methylamide spacer, prepared by condensation of the amine function of the contrast product with carboxymethylated dextran (CMD). The effect of various coupling reagents on the final yields is disucssed. Concerning the macromolecular features, all the synthesized products were characterized by acid‐base titration, elemental analysis, flame photometry, spectroscopic determinations and gel‐permeation chromatography. GPC showed that the carboxymethylation of dextran leads to some reticulation (doubling the molecular weights), whereas the coupling of CMD with the contrast compound does not alter the molecular weight and the polydispersity index of the products appreciably.
Chromophoric poly(vinyl alcohol derivative)s, 1. Synthesis and spectroscopical characterization of some poly(vinyl alcohol)s with alkoxyazobenzenecarbonyl substituents
Authors: Janietz Dietmar , Bauer Monika
Published: April 2003

The synthesis of new poly[(vinyl 4′‐alkoxyazobenzene‐4‐carboxylate)‐co‐(vinyl alcohol)]s 4a–c by Einhorn esterification of poly(vinyl alcohol) with 4′‐alkoxyazobenzene‐4‐carbonyl chlorides 3a–c prepared in two steps from 4′‐hydroxyazobenzene‐4‐carboxylic acid (1) is described. The degree of esterification is found to be about 85 mol‐%. Infrared, 1H and 13C nuclear magnetic resonance and ultraviolet spectroscopical data of the obtained polymers are determined.
Membrane of (polystyrene‐block‐polybutadiene‐block‐polystyrene)‐graft‐poly(2‐vinylpyridine) complexed with cobalt‐containing Schiff's bases for oxygen permeation
Authors: Hsiue Ging‐Ho , Yang Jen‐Ming
Published: April 2003

A study of the complex formation of (polystyrene‐block‐polybutadiene‐block‐polystyrene)‐graft‐poly(2‐vinylpyridine) (SBS‐graft‐VP) graft copolymers with a cobalt‐containing Schiff's base (1) in chloroform solution is here reported. The facilitated transport of molecular oxygen in SBS‐graft‐VP membranes containing various cobalt‐containing Schiff's bases as fixed carriers of oxygen is studied including oxygen permeability in SBS‐graft‐VP membranes and oxygen‐binding ability to a cobalt‐containing Schiff's base. Due to the reversible absorption of oxygen to SBS‐graft‐(VP‐1), the permeation of oxygen is remarkable for the lower upstream pressure, which can be explained by a dual mode.
Microstructure determination of acrylonitrile/butyl methacrylate copolymers using 13C NMR spectroscopy
Authors: Kapur Gurpreet Singh , Brar Ajaib Singh
Published: April 2003

Acrylonitrile/butyl methacrylate (A/B) copolymers were prepared in bulk with different comonomer feed ratios. The copolymer composition obtained from the total nitrogen content was used for calculating the reactivity ratios. Information about sequence distributions was obtained from 13C NMR spectroscopy. The relative amounts of A‐ and B‐centred triads were evaluated by using nitrile (CN) and carbonyl (CO) carbon resonances, respectively, and have been found to be in a good agreement with those expected theoretically.
Modification au deuxième degré de polymères époxydés, 3. Fixation de l'acide α‐naphtylacétique sur polyisoprène‐1,4 époxydé. Etude sur molécule modèle
Authors: Soutif Jean‐Claude , Klinpituksa Pairote , Brosse Jean‐Claude
Published: April 2003

The reaction of α‐naphthylacetic acid (1) (a plant growth stimulator) with 4,5‐epoxy‐4‐methyloctane (2) which reproduces the constitutional unit of epoxidized 1,4‐polyisoprene was studied. The rate of addition of the acid to the oxirane ring of 2 in chloroform with the tetramethylammonium salt of the acid 1 as catalyst increases with temperature, time, and concentration of the reagents.
Compatibility of tetramethyl polycarbonate and random poly(styrene‐co‐methyl methacrylate)s
Authors: Yu Dan , Hellmann Edit H. , Hellmann Gœtz P.
Published: April 2003

Phase diagrams and concentration fluctations of blends of tetramethyl polycarbonate (TMPC)

Polycarbonate of 2,2′,6,6′‐tetramethyl‐4,4′‐isopropylidenediphenol (tetramethyl derivative of bisphenol A).

and random copolymers P(SxMMA1−x) of styrene and methyl methacrylate were analyzed, using cast films and dry films. Phase separation was detected by light microscopy, DSC and small‐angle neutron scattering. Neutron scattering was also used to measure the structure of fluctuations in one‐phase as well as two‐phase states. The merits and problems of the various methods are discussed. Blends TMPC/P(SxMMA1−x) have high‐temperature miscibility gaps at x > 0,5. The copolymers interact non‐ideally, in a manner that had been observed before in their blends with PS and PMMA. An equation based on the classical theory but allowing diad effects describes the interaction parameters fairly well. It was used to calculate the interaction parameter of the immiscible homopolymer blend TMPC/PMMA which was also determined from the miscibility gap of a ternary blend TMPC/PMMA/P(SxMMA1−x).
Electroinitiated cationic polymerization of ε‐caprolactone using sacrificial anodes
Authors: Pierre Gérard , Limosin Danièle , Djelali Nacer‐Eddine
Published: April 2003

The polymerization of ϵ‐caprolactone is carried out with metallic cationic initiators generated electrochemically. V, Ti, Cr, Al and Hg cations gave rise to polymers with molecular weights in the range 1 000–13 000. Better yields and higher degrees of polymerization are obtained in the presence of [SbF6]− and [ClO4]− as anion of the supporting electrolyte, which is in accordance with the stability and the poor nucleophilicity of these anions.
Crosslinked polyethylene/polypropene blends, 1. Formation of insoluble parts, crystallization and melting
Authors: Chodák Ivan , Janigová Ivica , Romanov Andrej
Published: April 2003

Crosslinked blends of low density polyethylene/isotactic polypropene (LDPE/iPP) were studied over the whole composition range. The degree of crosslinking was determined from the gel content and the degree of swelling. In the presence of a coagent an efficient crosslinking of polypropene can be observed in blends whereas in the absence of the coagent only the PE component is crosslinked.

Thermal characterization of the blends by differential scanning calorimetry (DSC), i.e. heat of fusion, melting and crystallization temperatures suggest that the crosslinking results in the formation of a structure with molecules of both components being mutually connected. A two‐phase structure is still maintained and crosslinked molecules of polypropene (PP) and polyethylene (PE) are found at the interface.

The effect of crosslinking on the rate of crystallization is different for PE and PP. This phenomenon is explained by the superposition of the influence of crosslinking on the rate of crystal growth and nucleation.
Propriétés rhéologiques à l'état fondu de mélanges binaires de polyéthylène et de polybutène‐1
Authors: Deri Fawaz , Lallam Abdelaziz
Published: April 2003

The dynamic rheological study on a series of binary blends obtained from low‐density polyethylene and poly(1‐butene) was carried out. From our results we can propose an analogical pattern which is able to simulate the rheological behaviour of the blend in the melt state. We have calculated the different parameters of the model and their variations with temperature, composition, mixing and frequency. We have demonstrated that:

The viscosity η0 and the mean relaxation time τ0 decrease with increasing temperature, while the parameter h of the distribution of relaxation times remains independant of the temperature.

Kneading operation gives rise to a drop of the τ0, η0 and h values compared to those products which have not been kneaded.

The viscosity η0 is the weighted sum of the blend components.

The viscosity η0 of the blend is a function of the molecular weight.
External silane donors in Ziegler‐Natta catalysis. An approach to the optimum structure of the donor
Authors: Härkönen Mika , Seppälä Jukka V.
Published: April 2003

Our earlier work about alkoxysilanes as external donors in high‐activity Ziegler‐Natta catalysts is broadened with studies on the performance of some other oxygen‐containing silane compounds and with some studies on the effect of the structure of the hydrocarbon part of the alkoxysilane compounds: There are new informations about the optimum structure of an external silane‐type donor. The alkoxy group proved to be the best electron‐donating group, whereas the other oxygen‐containing electron‐donating groups tested worked less effectively. In some structures the oxygen atoms were sterically too hindered for effective deactivation. Some increase in the isotacticity was nevertheless observed even with the poor performance donors, which indicates that there could be a population of active centres that are very easy to deactivate. All the para‐substituted alkoxy phenyl silane donors tested gave polypropene with high isotacticity and activity. Therefore, we conclude that the nature of the substituent does not markedly affect the performance of the donor — at least as long as the substituent has not a sterically free electron‐donating group.
An investigation into the nature of the electrochemical and surface properties of polyacrylamides and a study of their adsorption onto the surface of papermaking woodpulps using alternating‐current polarography
Authors: Petzold James C. , Herrington Thelma M.
Published: April 2003

A cationic polyacrylamide was examined using polarography, constant potential coulometry, photon correlation spectroscopy, electrocapillarity and potentiometric titrimetry. A polarographic response was found in differential‐pulse polarography (DPP), direct‐current and Kalousek modes at −1,7 V versus a silver/silver chloride electrode. In each case the magnitude of the response was a function of polymer concentration. However, it is thought that the response is not due to the polymer itself but impurities found with it. These were found to have a pK of 4,75. The polymer appears to develop a more open structure in LiCl solution (<0,0013 mol/L). The unwashed polymer was found to greatly increase the interfacial tension at the mercury drop, but this effect was considerably reduced on washing the polymer in 70% acetone solution. Hydrolysis of the polymer seems to occur at pH 10. The suppression of the negative tensammetric peak of poly(ethylene glycol) (PEG200) by a range of cationic polyacrylamides was used for their analysis in the determination of their adsorption onto the surface of woodpulp. The adsorption was found to be a function of both their cationicity and mean molar mass. The rate of hemicellulose desorption from the woodpulp appears to be pH dependent. The impurity is thought to be mainly adipamic acid

Systematic name: 5‐carbamoylpentanoic acid.

.
Effect of alkyl groups on the rate constants of propagation and termination in the radical polymerization of dialkyl itaconates
Authors: Sato Tsuneyuki , Takahashi Yoshiko , Seno Makiko , Nakamura Hiroyuki , Tanaka Hitoshi , Ota Tadatoshi
Published: April 2003

Polymerization of dialkyl itaconates with dimethyl azoisobutyrate (5) was studied in benzene at 50°C by means of electron spin resonance (ESR). The monomers used are dimethyl (1), diethyl (2), dibutyl (3) and di‐2‐ethylhexyl (4) itaconates. All the polymerization systems involve ESR‐observable propagating polymer radicals under the actual polymerization conditions. The polymerization rate (Rp) and degree of polymerization of the resulting polymer increase in going from shorter to longer alkyl groups. The ESR‐determined rate constants of propagation (kp) and termination (kt) decrease as the alkyl chain becomes longer. kp of 1 is 3,3 times higher than that of 4, while kt of 1 is 590 times higher than that of 4. Thus, the steric effect due to the alkyl group suppresses much more termination than propagation, leading to the fact that Rp increases as the alkyl group becomes larger.
Association of macromolecular prodrugs consisting of adriamycin bound to poly(L‐glutamic acid)
Authors: Nukui Masahiro , Hoes Kees , van den Berg Hans , Feijen Jan
Published: April 2003

Soluble macromolecular conjugates for the controlled delivery of the strongly hydrophobic antitumor drug adriamycin (ADR) were prepared. The association behaviour of two types of these amphiphilic conjugates consisting of ADR bound to poly(L‐glutamic acid) (PGA) in aqueous solution was investigated using absorbance and fluorescence spectroscopy as well as GPC and lowangle laser light scattering (LALLS) measurements. ADR was bound via the aminoribosyl moiety either directly with PGA side‐chain groups or via oligopeptide spacer groups. UV/VIS, GPC and LALLS data showed that in buffer solution both ADR conjugates associate intermolecularly. The data of the directly bound ADR conjugates are consistent with the presence of multimers of different degrees of association in equilibrium with single polymer chains. In contrast, spacer‐containing ADR conjugates associate to give stable uniform multimers. UV/VIS and fluorescence spectroscopy performed at very low conjugate concentration show that polymer‐bound ADR residues associate intramolecularly as well. The degree of intra‐ and intermolecular association of the conjugate‐bound ADR molecules depends on the type of conjugate, ADR load and conjugate concentration as well as on ionic strength of the solvent, the presence of organic cosolvents and temperature. The data indicate that hydrophobic domains in spacer‐containing conjugates are more stable compared with directly bound conjugates, probably due to enhanced flexibility and the presence of hydrophobic leucine residues. It is concluded that spacer‐containing conjugates of ADR may have a potential for effective drug delivery under in vivo conditions due to their solution properties in addition to the biodegradability of the drug‐polymer bond.
Side‐chain liquid‐crystalline polysalts. Synthesis and thermal properties of poly{1‐[ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl]‐4‐vinylpyridinium bromide} or poly[1‐(2‐{2‐[2‐(4′‐methoxy‐4‐biphenylyloxy)ethoxy]ethoxy}ethyl)‐4‐vinylpyridinium bromide]
Authors: Navarro‐Rodriguez Dámaso , Frère Yves , Gramain Philippe
Published: April 2003

The synthesis and thermal properties of a new type of side‐chain liquid‐crystalline polymers, incorporating ionic groups, are described. The polymers are obtained upon spontaneous polymerization (simultaneous quaternization and polymerization) of 4‐vinylpyridine in the presence of ω‐(4′‐methoxy‐4‐biphenylyloxy)alkyl or 2‐{2‐[2‐(4′‐methoxy‐4‐biphenylyloxy)ethoxy]ethoxy}‐ethyl bromide. Fully quaternized polymers of high molecular weight are obtained. As the analogous low‐molecular‐weight molecules previously studied these polymers form smectic mesophases, although the mesogenic groups, which include the pyridinium rings, are directly connected to the polyvinylic backbone.
Synthesis of comb‐like methacryl polymers containing condensates of 11‐aminoundecanoic‐ and 6‐aminocaproic acid in the side chains
Authors: Niemann Manfred , Ritter Helmut
Published: April 2003

The synthesis and free‐radical polymerization of four methacrylic macromonomers, methyl 6‐(6‐methacryloylaminohexanoylamino)hexanoate (5), methyl 11‐(11‐methacryloylaminoundecanoylamino)undecanoate (6), and the corresponding acids 7 and 8, are described. The polymers were characterized by DSC and TG analysis. Viscosity measurements show that the polymers tend to associate because of hydrogen bonding. Additionally, incompatibility of the polymers with polyamide‐6 was found by DSC measurements.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 4. Synthesis of monomers with long alkyl side chains
Authors: Nuyken Oskar , Leitner Michael B. , Maier Gerhard
Published: April 2003

Homologues of the series 1,4‐bis(2‐methyl‐2‐alkenyl)benzene (6) are potential monomers for the systematic synthesis of alkyl‐substituted polyindans. The first five homologues were prepared by Witting‐synthesis, starting from 1,4‐diacetylbenzene (5) and the corresponding n‐alkyltriphenyl‐phosphonium bromide (3). Three double‐bond isomers were qualitatively and quantitatively identified by 1H and 13C NMR spectroscopy. The reaction conditions chosen favour Z‐olefination, and the selectivity ratio of Z‐ and E‐olefin formation in each step was estimated.
Effect of catalyst isospecificity on the copolymerization of propene with 1‐hexene
Authors: Sugano Toshihiko , Gotoh Yukitaka , Fujita Takashi , Uozumi Toshiya , Soga Kazuo
Published: April 2003

Copolymerization of propene with 1‐hexene was performed at 40°C under atmospheric pressure using both aspecific and isospecific catalysts composed of TiCl3/MgCl2 and Al(C2H5)3, and of Solvay type TiCl3 and Cp2 Ti(CH3)2 (Cp: cyclopentadienyl), respectively. The isospecific catalyst gave two kinds of copolymers with different content of 1‐hexene, whereas the aspecific catalyst gave a uniform copolymer abundant in 1‐hexene. Both copolymers produced with the isospecific catalyst were found to show isotactic stereoregulation in the propylene units. From these results, it was concluded that the catalyst composed of Solvay type TiCl3 and Cp2 Ti(CH3)2 has two kinds of isospecifically active species which differ in the monomer reactivity ratio for propene‐1‐hexene copolymerization.
Enzymatic degradation of microbial poly(3‐hydroxybutyrate) films
Authors: Kumagai Yoshiharu , Kanesawa Youko , Doi Yoshiharu
Published: April 2003

The effects of crystallinity and spherulite size on the enzymatic degradation of microbial poly(3‐hydroxybutyrate) (PHB) films have been studied at 37°C and pH 7,4 in aqueous solutions of an extracellular PHB depolymerase from Alcaligenes faecalis T1. The rate of enzymatic degradation of PHB films decreases with an increase in crystallinity, but it is little influenced by the size of PHB spherulites. It was suggested that the PHB depolymerase firstly hydrolyzes the PHB chains in the amorphous state on the surface of the films and subsequently erodes the PHB chains in the crystalline state.
Hydroquinone oxidation catalyzed by pyridine‐Cu(II) complexes attached to polyorganosiloxanes
Authors: Nemoto Nobukatsu , Ishii Hiroji , Ueno Yukihiko , Ikeda Koji , Takamiya Nobuo
Published: April 2003

Cu(II) complexes of polyorganosiloxanes with pyridyl group in the side chains (1–6) were investigated as catalysts for hydroquinone oxidation. The catalytic oxidations followed Michaelis‐Menten‐like kinetics. The kinetic parameters were evaluated, and the greatest value of k2/Km is 119 dm3 · mol−1 · s−1 due to the large value of k2 (0,262 s−1) in methanol/water (vol. ratio 2/1) at 25°C. It has been shown that the main factors which influence the substrate‐binding process are hydrophobicity, hydrogen bonding between functional groups in the side chains, conjugation and basicity of pyridine, and adsorption of substrate by amido groups. Large k2 values were obtained in the present system due to flexibility and hydrophobicity of the siloxane backbone. Additionally, in the activation process, hydrogen bonding between amido groups, which is easily formed due to the flexibility of the polymer chains, should contribute to decrease both activation enthalpy and activation entropy.
Mechanisms and kinetics of the anionic polymerization of acrylates, 2. Polymerization of tert‐butyl acrylate in a flow tube reactor and effect of lithium chloride and lithium tert‐butoxide
Authors: Janata Miroslav , Lochmann Lubomír , Vlček Petr , Dybal Jiři , Müller Axel H. E.
Published: April 2003

The kinetics and the molecular weight distributions (MWD) in the anionic polymerization of tert‐butyl acrylate (tBuA) in tetrahydrofuran at 23 ± 3°C were investigated. Tert‐butyl α‐lithioisobutyrate (tBiB‐Li) was used as the initiator in the absence and presence of the additives lithium chloride and lithium tert‐butoxide (tBuOLi). A flow tube reactor was used which allowed very rapid mixing of reagents, within milliseconds. The polymerization is extremely fast, half‐lives being 0,01 s for the system without additive, 0,05 s for LiCl and 3 s for tBuOLi as an additive. The rate of termination was estimated from the strong UV absorption of the enolized β‐oxoester end group formed. The number‐average degree of polymerization is a linear function of conversion, the absolute values, however, demonstrate initiator efficiencies of only ca. 30%. The MWD's of the polymers formed are narrow (Mw/Mn = 1,35 without additive, M/Mn = 1,08 in the presence of LiCl and Mw/Mn = 1,77 in the presence of tBuOLi). After precipitation these values are reduced to 1,17; 1,06 and 1,32, respectively. Experiments in a stirred tank reactor and in ampoules lead to much broader MWD's. This shows that the rate of mixing has a strong effect on the MWD and is of substantial importance in these rapid polymerizations.
Flory polymer‐polymer interaction parameter between hemicellulose and lignin from hardwood
Authors: Shigematsu Mikiji , Morita Mitsuhiro , Sakata Isao
Published: April 2003

The interaction parameter between hemicellulose and lignin from beech wood was evaluated from vapor pressure osmometric measurements on solvent‐polymer and solvent‐polymer‐polymer solutions. Dimethyl sulfoxide (DMSO) was used as a solvent. The interaction parameters between hemicellulose and DMSO (χ01) and between lignin and DMSO (χ02) increase with increasing temperature, and the change with temperature is proportional to inverse temperature. It was found for both polymers that DMSO becomes a “poor solvent” at higher temperature. This result was also derived from the free energy of dilution. The interaction parameter between hemicellulose and lignin (χ12) was evaluated as a function of temperature from the activity of solvent in a solution of the three components. At 60°C, χ12 is positive; it decreases with increasing temperature and becomes negative at 70–80°C where a minimum is found. Above 80°C, χ12 increases again to become positive at 90°C. Thus, hemicellulose and lignin attract each other at 70–80°C, but there is repulsion between the polymers at higher and lower temperatures.
Influence du vieillissement d'une solution renfermant un polystyrène silicié et un sel de triarylsulfonium sur le pourcentage de coupure des liaisons OSi sous irradiation ultraviolette et en couche mince
Authors: Bonfils Frédéric , Giral Louis , Montginoul Claude , Sagnes René , Schué Franc̨ois
Published: April 2003

Upon treatment with ultraviolet irradiation (wavelength λ = 254 nm) the resist containing both poly(p‐trialkylsiloxystyrene) and a triarylsulfonium salt undergoes photoinduced structural modifications which convert the silylated polymer into either poly(p‐hydroxystyrene) or poly[(p‐trialkylsioxystyrene)‐co‐(p‐hydroxystyrene)]. Aging with the use of antimonate salts rather than arsenate salts, and bulky alkyl groups favour OSi bond cleavage.
Radical‐intiated copolymers of styrene and p‐formaylstyrene, 2. Preparation and characterization of emulsifier‐free copolymer latices
Authors: Charleux Bernadette , Fanget Philippe , Pichot Christian
Published: April 2003

Monodisperse copolymer latex particles with aldehyde groups at the surface have been prepared by a two‐step process, comprising first a soap‐free emulsion polymerization of styrene using potassium peroxodisulfate as an initiator and secondly a surface functionalization of the seed particles by copolymerizing p‐formylstyrene (system. name: 4‐vinylbenzaldehyde) using various addition methods. The final latices were characterized with respect to monomer conversion, copolymer composition, particle size and distribution. Particular attention was paid to the characterization of surface aldehyde groups using two different analytical methods such as X‐ray photoelectron spectroscopy (XPS) and radioactive labelling by coupling with (1‐3H1)‐2‐aminoethanol.
Asymmetric radical‐initiated copolymerization of (−)‐menthyl sorbate with styrene
Authors: Doiuchi Tohru , Dodoh Takeshi , Yamaguchi Hidemasa
Published: April 2003

The radical‐initiated copolymerization of (−)‐menthyl sorbate ((−)‐3‐p‐menthyl 2,4‐hexadienoate) with styrene was carried out in benzene with 2,2′‐azoisobutyronitrile as an initiator at 50°C to give an optically active copolymer 1. While the chiral menthyl group of the copolymer was removed by hydrolysis with aqueous alkali, the hydrolyed copolymer was still optically active. Therefore, asymmetric induction must have occurred during copolymerization.
Influence of molecular weight and concentration of poly(2‐vinylnaphthalene) on the bulk polymerization of styrene under UV‐irradiation in the presence of a magnetic field
Authors: Huang Junlian , Zhu Ping , Ji Caigui , Ruan Weixiang
Published: April 2003

The effect of molecular weight and concentration of poly(2‐vinylnaphthalene) (PVN) on the bulk polymerization of styrene initiated by 2,2′‐azoisobutyronitrile (AIBN) was studied under UV‐irradiation in the presence of a magnetic field. It was found that in the suitable range of molecular weights (<1,7 · 103) and concentrations (1,62 to 9, 12 · 10−3 mol/L) of PVN, the molecular weight and molecular weight distribution of polystyrene significantly varied with the change of the external magnetic field. A triplet energy transfer mechanism between PVN and AIBN in the PVN cages was suggested on the basis of the experimental results.
Polymethacrylate graft copolymers with a liquid‐crystalline component
Authors: Hefft Marita , Springer Jürgen
Published: April 2003

This paper reports on the synthesis and characterization of graft copolymers built up by amorphous poly(methyl methacrylate) grafts and a side‐chain liquid‐crystalline backbone. The interest was focussed on the copolymerization behaviour of the liquid‐crystalline monomers and styryl‐terminated methyl methacrylate macromonomers. The radical polymerization of the liquid‐crystalline monomers depends on the liquid‐crystalline monomer concentration and on the amount and length of the grafts (macromonomers). The liquid‐crystalline backbone is the longer the higher the concentration of the mesogenic monomers itself and the smaller the molecular weight of the macromonomers. Variation of the amounts of grafts yielded a maximum length of the liquid‐crystalline backbone at approximately 4 mol‐% (for a molecular weight of 7800 of the graft).
Electrochemical polymerization of 1H,7H‐pyrrolo[2′,3′:4,5]‐thieno[3,2‐b]pyrrole and 4H‐dithieno[3,2‐b;2′,3′‐d]pyrrole
Authors: Berlin Anna , Pagani Giorgio , Zotti Gainni , Schiavon Gilberto
Published: April 2003

Electrochemical polymerization of 1H,7H‐pyrrolo[2′,3′:4,5]thieno[3,2‐b]pyrrole and 4H‐dithieno[3,2‐b;2′,3′‐d]pyrrole in CH3CN + 0,1 M p‐toluenesulfonate and tetraethylammonium perchlorate, respectively, yields polymers with a conductivity of ca. 5 S/cm. Electrochemistry and elemental analysis indicate the presence of 0,6‐0,7 anions per monomeric unit, while spectroelectrochemistry agrees with a polypyrrole structure for polypyrrolothienopyrrole and a polythiophene structure for polydithienopyrrole. The redox cycle for polypyrrolothienopyrrole (at −0,53 V vs. Ag/Ag+) is close to that of polypyrrole, while that of polydithienopyrrole (at 0,0 V) is intermediate between those of polythiophene and polypyrrole. N‐Alkylsubstituted dithienopyrroles produce soluble polymers with higher conductivity (40 S/cm) and the lowest band‐gap (1,7 eV) ever reported for a polythiophene‐like polymer.
New poly(amide‐imide) syntheses, 3. Preparation and properties of cardo poly(amide‐imide)s derived from 9,9‐bis(4‐aminophenyl)fluorene, trimellitic anhydride, and various aromatic diamines
Authors: Yang Chin‐Ping , Cheng Ju‐Ming , Hsiao Sheng‐Huei
Published: April 2003

An imide‐ring‐containing dicarboxylic acid, N,N′‐(9‐fluorenylidenedi‐1,4‐phenylene)diphthal‐imide‐4‐carboxylic acid (1), was prepared by condensation of trimellitic anhydride and 9,9‐bis(4‐aminophenyl)fluorene. A series of new aromatic cardo poly(amide‐imide)s having inherent viscosities of 0,59‐1,13 dL/g were prepared by the direct polycondensation of this diimide‐diacid with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents in 1‐methyl‐2‐pyrrolidone (NMP) in the presence of calcium chloride. The polymers are amorphous and readily soluble in highly polar solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, NMP, and m‐cresol. Transparent and tough films can be easily cast from the polymer solutions. The glass transition temperatures of these poly(amide‐imide)s are above 320°C. Thermal analyses indicated that these polymers are fairly stable, and the 10% weight loss temperatures were recorded in the range of 532–622°C in nitrogen atmosphere.
Electrochemical synthesis of poly(p‐phenylene) in an ionic liquid
Authors: Kobryanskii Valery M. , Arnautov Sergei A.
Published: April 2003

Flexible transparent high‐molecular‐weight (degree of polymerization higher than 90) films of poly(p‐phenylene) were obtained by electrochemical polymerization of benzene in an aluminium chloride and N‐butylpyridinium chloride based ionic liquid. Effects of the process parameters on the structure and relative molecular mass of the samples were studied. A hypothesis which considers the role of doping of macromolecules generated in the process of the polymer synthesis, is proposed.
Polyesters containing both rod‐like and disc‐like mesogens
Authors: Karthaus Olaf , Ringsdorf Helmut , Ebert Martina , Wendorff Joachim H.
Published: April 2003

The synthesis of a new type of combined polymers containing both disc‐ and rod‐like mesogens is reported. The polyesters, having a triphenylene derivative as a discotic mesogen in the side group and azobenzene or biphenyl derivatives as rod‐like mesogens in the main chain were characterized by polarizing microscopy, differential scanning calorimetry, and X‐ray scattering studies. The homopolymer 7 is highly crystalline, while the copolymer 8 is amorphous, both, however, do not form liquid‐crystalline phases.
New aspects in the anionic polymerization of phenyl glycidyl ether
Authors: Stolarzewicz Andrzej , Grobelny Zbigniew
Published: April 2003

A kinetic equation describing the anionic polymerization of phenyl glycidyl ether initiated by potassium anions in the presence of 18‐crown‐6 was derived. Rate constants of growth and chain transfer reactions were calculated. The equilibrium constant of complex formation by the active centre with alcohol being a product of chain transfer reactions was also evaluated.
A KrF excimer laser induced dehydrochlorination of a chlorinated poly(vinyl chloride): Preparation of conjugated polyene and polyyne
Authors: Shimoyama Masashi , Niino Hiroyuki , Yabe Akira
Published: April 2003

The photochemical dehydrochlorination of a chlorinated poly(vinyl chloride) film was investigated with respect to the preparation of a π‐electron‐conjugated polymer. The dehydrocholorination proceeds more effectively upon irradiation with a KrF excimer laser than with a low‐pressure mercury lamp, showing the formation of new absorption bands in the range 300–800 nm. The most effective condition provided KrF excimer laser irradiation of 25− 30 mJ/cm2 at 1 Hz in a vacuum chamber of 10−6 Torr at 90°C. The surface of the irradiated film was analyzed by IR (attenuated total reflection method), X‐ray photoelectron and Raman spectroscopy. The characteristic peaks (1 112, 1 488 and 2 188 cm−1) in the Raman spectrum were ascribed to a structure having eight conjugated CC bonds and twenty conjugated CC bonds.
A new radical cation salt: Electrocrystallization of trans‐1,2‐bis(2‐naphthyl)ethene and model character of the resulting salt for conducting arylenevinylene polymers
Authors: Stenger‐Smith John D. , Lenz Robert W. , Enkelmann Volker , Wegner Gerhard
Published: April 2003

A single‐crystal radical cation salt was obtained by anodic oxidation of trans‐1,2‐bis‐(2‐naphthyl)ethene (1,2‐DNE) with SbF−6 as the counter‐ion. The crystal structure of (1,2‐DNE)SbF6 was solved and found to be similar to the radical cation salts of unsubstituted naphthalene. The crystal structure is disordered, i.e. two orientations of the 1,2‐DNE molecules are statistically occupied. The molecular overlap, resulting from these two orientations, models the structure of the salt of poly(2,6‐naphthylenevinylene). In contrast to most other radical cation salts which are one‐dimensional conductors, a conduction mechanism of higher dimensionality is predicted on the basis of the crystal structure of (1,2‐DNE)SbF6. The identical type of disorder is also present in the crystal structure of trans‐1,2‐bis(1‐naphthyl)ethene.
Synthesis, dilute solution properties and chain flexibility of poly(diesters) of itaconic acid, 2, poly(methyl decyl itaconate)
Authors: León Arturo , Gargallo Ligia , Radić Deodato , Bravo Julio , Horta Arturo
Published: April 2003

The diester of itaconic acid with decyl and methyl groups was prepared and polymerized. The dilute solution behaviour of poly(methyl decyl itaconate) poly{1‐(decyloxycarbonylmethyl)‐1‐(methoxycarbonyl)ethylene} (PMeDI) was studied in tetrahydrofuran and 1‐butanol at 298 K, by light scattering, size‐exclusion chromatography, and viscometric measurements. The empirical Kuhn‐Mark‐Houwink‐Sakurada relationships were established. The molecular parameters were calculated using one theory of the excluded volume.
Comparison of zirconocene and hafnocene catalysts for the polymerization of ethylene and 1‐butene
Authors: Heiland Kirstin , Kaminsky Walter
Published: April 2003

In polymerizations with ethylene and copolymerizations with ethylene and 1‐butene the catalyst system rac‐ethylene(bisindenyl)zirconium dichloride (rac‐Et(Ind)2ZrCl2)/methylaluminoxane (MAO) shows lower activities than the analogous Hafnium catalyst. The polymers obtained with the hafnium‐catalyst have average molar masses up to ten times higher than those synthesized with the zirconium compound. It is remarkable that rac‐Et(Ind)2HfCl2 is much more able to incorporate the comonomer. This is expressed by the copolymerization parameters. At a polymerization temperature of +30°C, e.g., the r1‐parameter of the hafnium‐catalyst is 5,4, the corresponding parameter of the zirconium catalyst is 19,4. Polymerizations with a catalyst mixture rac‐Et(Ind)2(Hf, Zr)Cl2 (containing 95% rac‐Et(Ind)2HfCl2 and 5% rac‐Et(Ind)2ZrCl2) show that each catalyst compound produces its own polymer independently.
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

Epitaxial 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

UV 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

An 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

Hydrogenation 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

Polyesters 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.