bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethylene polymerization initiated by SiO2‐supported neodymocene catalysts
Authors: Jin Jizhu , Uozumi Toshiya , Soga Kazuo
Published: April 2003

Some SiO2‐supported neodymocene catalysts were prepared and polymerization of ethylene was conducted with them using alkylaluminiums, methylaluminoxane (MAO), BuLi and Bu MgEt (Bu: butyl, Et: ethyl) as cocatalysts. The lifetime of these catalysts was found to be very long. Catalytic activity as well as molecular weight of the produced polymer are strongly dependent upon kind and amount of cocatalyst used. With increasing polymerization temperature, the activity increases monotonously up to 80°C. The use of BuMgEt and Al(i‐C4H9)3 as cocatalyst gives the highest activity and highest molecular weight, respectively.
UV‐initiated solidification of liquid crystalline ethylcellulose/acrylic acid films and bands formed in this process
Authors: Zhao Chun‐tian , Cai Bao‐lian
Published: April 2003

Solidification of liquid crystalline ethylcellulose/acrylic acid films was realized by UV‐initiated polymerization of the solvent acrylic acid. It has been found that the original textures were immobilized to a great extent, and a novel “banded texture” formed at the same time. The optical properties of this texture were different from the banded texture formed by shearing lyotropic or thermotropic polymer liquid crystals. Formation of such bands is assumed to be related to an uncompleted phase separation.
Isotactic cis‐1,4‐poly(3‐methyl‐1,3‐pentadiene): a new conformation for isotactic cis‐1,4‐polydienes
Authors: Meille Stefano Valdo , Capelli Silvia , Allegra Giuseppe , Ricci Giovanni
Published: April 2003

Oriented specimens of isotactic cis‐1,4‐poly(3‐methyl‐1,3‐pentadiene) exhibit two crystalline modifications characterized, respectively, by the expected two‐fold helical conformation with a fiber repeat of 8,02 Å and by a three‐fold helix with c = 9,97 Å. The latter highly contracted structure is prevalent in fibers and is the only one observed in unoriented bulk specimens. Consistent with these findings conformational calculations indicate that the three‐fold helix is substantially more stable than the two‐fold one.
Synthesis and characterization of a chlorofunctionalized unsaturated carbosilane oligomer
Authors: Cummings Sophia K. , Smith Dennis W. , Wagener Kenneth B.
Published: April 2003

Acyclic diene metathesis (ADMET) polymerization offers a viable route for the synthesis of chlorofunctionalized unsaturated carbosilane oligomers. The SiCl bond in unsaturated carbosilane monomers remains inert during metathesis and the use of a highly reactive molybdenum‐based, Lewis acid‐free alkylidene catalyst affords unsaturated chlorofunctionalized carbosilane oligomers with known vinyl end groups. The first synthesis of an unsaturated carbosilane oligomer functionalized with a SiCl bond was performed. A chlorofunctionalized silacyclopentene product was also observed, due to a backbiting reaction. This new class of functionalized oligomers has a low glass transition temperature and sites of unsaturation which may be used for further reaction. ADMET chemistry now provides access to a variety of chlorofunctionalized unsaturated carbosilanes which can be used to tailor make hydrolytically stable carbosilane oligomers and polymers via nucleophilic grafting reactions.
The influence of the transition metal and the heteroatomic‐bridge on the action of metallocene/methyl aluminoxane catalysts in ethylene polymerization and on the properties of the polymer
Authors: Quijada Raul , Dupont Jairton , Silveira Dione Corrêa , Miranda Márcia S. Lacerda , Scipioni Rosângela B.
Published: April 2003

This work reports a comparative study of the catalytic behaviour for a series of metallocenes derived from Ti, Zr, Hf and Nb, which after activation with methylaluminoxane can polymerize ethylene. Results show that the Zr metallocene with a (CH3)2SiBridge presents the highest activity, and the metallocenes based on Hf and Nb do not show any significant activity under the tested conditions.
Synthesis and mesomorphic behavior of poly(dipropylsilylenemethylene)
Authors: Koopmann Florian , Frey Holger
Published: April 2003

Based on the reaction of trichloro(chloromethyl)silane (1) with 2 equivalent amounts of the respective Grignard‐reagent and subsequent cyclization, 1,1,3,3‐tetrapropyldisilacyclobutane (3) has been prepared. Catalytic polymerization with H2PtCl6 was employed to prepare the corresponding poly(dipropylsilylenemethylene) (PDPSM, 4) with strictly alternating SiR2/CH2 backbone structure. A high‐molecular‐weight fraction of the material (weight‐average molecular weight M̄w = 166 500 and number‐average molecular weight M̄n = 115 200) obtained by fractionating precipitation was investigated with respect to glass transition and formation of conformationally disordered mesomorphic phases. The glass transition temperature Tg = 232 K of PDPSM evidenced lower backbone flexibility than observed for the analogous poly(dipropylsiloxane), (PDPS). PDPSM exhibited mesomorphic behavior. In contrast to poly(dipropylsiloxane), PDPSM showed a surprisingly narrow mesomorphic regime between 355 K and 365 K. Based on polarizing microscopy and 29Si‐MAS (magic angle spinning) solid‐state NMR the mesophase is described as a conformationally disordered state, which is most probably columnar in analogy to PDPS.
Characterization of polybutadiene produced with CoBr2(PPh3)2‐based catalysts
Authors: Takeuchi Masaki , Shiono Takeshi , Soga Kazuo
Published: April 2003

Polymerization of 1,3‐butadiene was conducted with the CoBr2(PPh3)2(Ph: phenyl)‐methylaluminoxane (MAO) and MgCl2‐supported CoBr2(PPh3)2‐Al(CH3)3 catalyst systems. The microstructure of polybutadiene was analyzed in detail by 13C NMR spectroscopy after hydrogenation, which indicated that the distribution of the 1,2 and 1,4 units in polybutadiene is more random when the homogeneous CoBr2(PPh3)2‐MAO catalyst was used. The microstructure of these polymers was compared with that obtained using BuLi as catalyst.
Bifunctional polytetrahydrofuran initiator for sequential photochemical and thermal initiation
Authors: Denizligil Selcuk , Baskan Aysegul , Yagci Yusuf
Published: April 2003

The polymerization of tetrahydrofuran was initiated with 4,4′‐azobis(4‐cyanovaleryl chloride) in conjunction with silver hexafluoroantimonate and the living polytetrahydrofuran (PTHF) was terminated with pyridinium N‐oxide derivatives. The resulting PTHF‐macroinitiator possesses both a thermally and photochemically labile group.
Polymerizable mesoions, 2. Radical polymerization and 1,4‐dipolar polycycloaddition of a 4‐vinylphenyl‐modified mesoionic 4,6‐dioxo‐1,3‐diazine
Authors: Ritter Helmut , Sperber Rolf
Published: April 2003

Mesoionic 5‐methyl‐4,6‐dioxo‐3‐phenyl‐1‐(4‐vinylphenyl)‐1,3‐diazine (5) was obtained by condensation of 3‐phenyl‐1‐(4‐vinylphenyl)formamidine (3) with methylmalonic acid (4). This vinyl‐substituted mesoionic heterocyclic compound was polymerized by usual radical initiation and, additionally, by thermally controlled polycycloaddition in solution, yielding two different types of polymers, 6, 7. According to the X‐ray diffraction analysis, the structure of a low molecular weight model proves the regioselectivity of the polycycloaddition.
Synthesis of poly(tert‐butoxycarbonyl‐p‐phenylene): precursor to poly(p‐phenylene)
Authors: Ueda Mitsuru , Yoneda Masanobu
Published: April 2003

Poly[2‐(tert‐butoxycarbonyl)‐1,4‐phenylene] (2) was prepared by the Ni‐catalyzed polymerization of tert‐butyl 2,5‐dichlorobenzoate (1). The microstructure of polymer 2 was probably alternating head‐to‐head and tail‐to‐tail. This polymer was soluble in dipolar aprotic solvents, chloroform, tetrahydrofuran, and dichloromethane. Polymer 2 was saponified easily by thermal or acid treatment to yield poly[2‐carboxy‐1,4‐phenylene] (3). Decarboxylation of polymer 3 in quinoline in the presence of copper(II) oxide produced poly(p‐phenylene) (PPP) (4).
Kinetic study of free‐radical copolymerization of ethyl α‐benzoyloxymethylacrylate with methyl methacrylate in benzene
Authors: Cuervo‐Rodríguez Rocío , Fernández‐Monreal M Carmen , Fernández‐García Marta , Madruga Enrique L.
Published: April 2003

From a phenomenological point of view, the Mayo‐Lewis terminal model can describe both copolymer composition and the variation of copolymerization rate for the ethyl α‐benzoyloxymethylacrylate/methyl methacrylate/benzene/2,2′‐azoisobutyronitrile system.
Synthesis of hydroxy‐terminated poly(vinyl ethers) by living cationic polymerization, 2. Poly(2‐chloroethyl vinyl ether): a telechelic polymer with reactive pendants
Authors: Hashimoto Tamotsu , Aizawa Hideaki , Kodaira Toshiyuki
Published: April 2003

Hydroxy‐terminated telechelic poly(2‐chloroethyl vinyl ether) (poly(CEVE)) was synthesized by water‐based end‐capping reaction of living poly(CEVE) with the initiating system CH3CHClOCH2CH2OCOCH3/ZnCl2 in CH2Cl2 at −40°C and subsequent end‐group transformation of the acetate (α‐end) and aldehyde (ω‐end) groups into hydroxy groups. The obtained polymers possess controlled molecular weights and narrow molecular weight distributions.
Block copolymer with liquid‐crystalline polyacrylate and poly(propylene oxide) segments
Authors: Gomes Aílton S. , Carvalho Kalen S. , Pinto Maurício R.
Published: April 2003

A new route of synthesis of block copolymers was investigated. It involves the polymerization of a side‐chain liquid‐crystalline acrylate and poly(propylene glycol), modified by an esterification reaction with mercaptoacetic acid used as macrotransfer agent, in the presence of 2,2′‐azoisobutyronitrile as initiator. The molecular weight of the liquid‐crystalline blocks is determined by the molar ratio between the reactants.
Polypyridine block as molecular antenna in photoluminescence of macromolecular systems
Authors: Yamamoto Takakazu , Yoneda Yutaka , Kizu Kenichi
Published: April 2003

Unique effects of π‐conjugated polypyridine (PPy) blocks on fluorescence from the following macromolecular systems have been examined: (A) poly(2,2′‐bipyridine‐5,5′‐diyl) (PBpy)‐Ru(bpy)2, (b) block‐type copolymer of pyridine and selenophene, and (c) a system containing poly(6‐hexylpyridine‐2,5‐diyl) (6HexPy) and poly(2‐methylanthraquinone‐1,4‐diyl) (P2MeAQ). The PPy blocks in the systems serve as good molecular antennas and transfer the photoactivated energy to other molecular parts of the systems connected to the PPy blocks, thus causing emission of light from the other molecular parts.
Acyclic diene metathesis (ADMET) depolymerization: The synthesis of 1,4‐polybutadiene telechelics
Authors: Wagener Kenneth B. , Marmo J. Christopher
Published: April 2003

ADMET depolymerization is a viable route in the formation of tailored‐molecular‐weight polybutadiene telechelics. The bulk depolymerization requirement is met by initially forming macrocyclic butadiene, thereby decreasing the amount of macrocyclic formation. This synthetic scheme is capable of generating well‐defined, tailored‐molecular‐weight polybutadiene telechelics (M̄n = 2600).
Copolymerization of 1,3‐butadiene and styrene with a neodymium catalyst
Authors: Oehme Annekatrin , Gebauer Ulrich , Gehrke Klaus , Lechner M. Dieter
Published: April 2003

Homo‐ and copolymerization of butadiene and styrene in the presence of the catalyst system Nd(octanoate)3/CCl4/Al(iBu)3 (iBu: isobutyl) were investigated at 60°C in heptane as solvent. The initiating catalyst system is very effective in the polymerization of butadiene. However, the presented copolymerization of butadiene and styrene is only practicable when using a special addition order of the catalyst components and a prescribed ageing phase. Copolymers obtained from various monomer feed ratios were characterized by 1H and 13C NMR spectroscopy and gel‐permeation chromatography (GPC). The copolymer characteristics especially microstructure, molar mass and molar‐mass distribution (MMD) are strongly dependent on the composition of the monomer mixture.
Highly oxygen permselective membrane prepared from cobalt‐complexed polyazomethine containing a ligand and a tri‐ or tetrasiloxane in the main chain
Authors: Shin Kyounghan , Aoki Toshiki , Oikawa Eizo
Published: April 2003

Two types of polyazomethines containing repetitive pairs of a tridentated ligand and an oligodimethylsiloxane in the backbone were synthesized and complexed with cobalt ion. The resulting polymer complex membranes showed very good oxygen permselectivity at 1 atm pressure difference, which is very close to the upper boundary line in an α vs. Po2 plot of data reported in the literature. The complexes are thought to function as oxygen carrier.
Formation of block copolymer micelles in solutions of a linear homopolymer in a good solvent
Authors: Quintana José R. , Jáñez María D. , Katime Issa
Published: April 2003

The existence of micelles of polystyrene‐block‐poly(ethylene/propene) in solutions of polystyrene in toluene was investigated. Toluene is a good solvent of both copolymer blocks whereas polystyrene and poly(ethylene/propene) are immiscible polymers. The presence of homopolystyrene at high enough concentration can induce the micellization of polystyrene‐block‐poly(ethylene/propene) in solution of a good solvent such as toluene. The thermodynamics of this new micelle system at a given polystyrene concentration was studied. Light scattering measurements were carried out in order to determine the critical micelle temperature (CMT) of different micellar solutions. Standard Gibbs energy, enthalpy and entropy of micellization were estimated from CMT and concentration data. The numerical values found were less negative than those found for micelle systems consisting in a block copolymer dissolved in a single selective solvent.
Enzyme‐catalyzed syntheses of poly(1,6‐hexanediyl maleate) and poly(1,6‐hexanediyl fumarate) in organic medium
Authors: Mezoul Gilles , Lalot Thierry , Brigodiot Maryvonne , Maréchal Ernest
Published: April 2003

The lipase‐catalyzed preparation of poly(1,6‐hexanediyl maleate) by transesterification of 1,6‐hexanediol and dimethyl maleate is described. A configurationally pure poly(1,6‐hexanediyl maleate) exhibiting exclusively cis structure was obtained. During the reaction, a substantial amount of macrolactones was formed. They were isolated, and the cyclic oligomer with y = 2 was found to predominate. Cycles are semi‐crystalline, while no melting point was detected for the linear poly(1,6‐hexanediyl maleate). We assume that the linear unsaturated polyester is completely amorphous owing to its cis configuration.
Structure formation of liquid‐crystalline isotropic AB block copolymers in nematic solvents
Authors: Walther Mathias , Bohnert Robert , Derow Stephan , Finkelmann Heino
Published: April 2003

AB block copolymers with an isotropic and a nematic block are synthesized by living anionic copolymerization of isotropic and mesogenic methacrylates. The complete phase diagrams of the corresponding homopolymers with the nematic solvent have been established. In dilute solution (0.2 to 5% by weight) in a low‐molar‐mass nematic solvent, the copolymers exhibit two different types of structure formation. Polymers with high isotropic block fraction form irreversible networks as a results of phase separation followed by vitrification of the polymer‐rich phase. Polymers with high nematic block fraction on the other hand form thermoreversible threadlike structures perfectly ordered parallel to the director of the nematic solvent. These structures cannot be explained by a macroscopic phase separation process but more likely by a formation of micellar‐like aggregates.
Doublestimuli‐responsive degradable hydrogels for drug delivery: Interpenetrating polymer networks composed of oligopeptide‐terminated poly(ethylene glycol) and dextran
Authors: Kurisawa Motoichi , Terano Minoru , Yui Nobuhiko
Published: April 2003

Biodegradable hydrogels composed of oligopeptide‐terminated poly(ethylene glycol) (PEG) and dextran with interpenetrating polymer network (IPN) structure were proposed as a novel substrate for multistimuli‐responsive drug delivery. IPN‐structured hydrogels were synthesized by sequential crosslinking reactions of N‐methacryloyl‐glycilglycilglycil‐terminated PEG and dextran. In vitro degradation of the IPN‐structured hydrogels was examined using papain and dextranase as model enzymes for hydrolyzing the oligopeptide and the dextran. Specific degradation in the presence of papain and dextranase was observed in the IPN‐structured hydrogel with a particular composition of PEG and dextran, whereas this hydrogel was not degraded by one of the two enzymes.
A polarographic study of propene‐maleic anhydride copolymers
Authors: Werner Kirsten , Steinert Volker , Reinhardt Steffi
Published: April 2003

The polarographic behaviour of hydrolyzed propene‐maleic anhydride copolymers in the interval pH 2.0–11.0 has been investigated by differential pulse polarography in aqueous lithium chloride solution at 25°C. In dependence on the pH‐value, one, two or three signals, belonging to the acid groups in the copolymer, appear in the polarograms. Three apparent polarographic acid constants have been determined graphically from the changes in the half‐wave potential of the separate peaks in correlation with pH.
Towards periodic copolymers with flexible and mesogenic units in the main chain. Copolymerization of tetrahydrofuran with 7‐oxabicyclo[2.2.1]heptane
Authors: Libiszowski Jan , Szymanski Ryszard , Penczek Stanislaw
Published: April 2003

An attempt was made to prepare periodic polymers having promesogenic units of various lengths. Due to a certain distribution within these units, copolymers of this structure should rather be called pseudoperiodic. In order to understand better the behaviour of such systems, copolymerization of tetrahydrofuran (THF — soft units) with 7‐oxabicyclo[2.2.1]‐heptane (BC — hard units) was studied. The kinetically and thermodynamically controllable copolymerizations were elaborated, leading to products of different distribution of the THF and BC units. The apparent reactivity ratios are dependent on the copolymerization conditions due to the reversibility of the propagations on the THF type of active species. They vary: r̄1 from 0.09 to 2.72, r̄2 from 0.31 to 1.57 (1 stands for BC, 2 for THF). Pseudoperiodic copolymers of the structure \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{-} [\rlap{–} ({\rm BC}\rlap{-} )_x {\rm THF}\rlap{-} ]_n $\end{document}, where x̄ = 1 to 4, were prepared carrying out the copolymerization above the ceiling temperature of THF.
One‐step synthesis of 2,6‐naphthalenedicarboxylic acid from naphthalene using cyclodextrin as catalyst
Authors: Hirai Hidefumi , Shiraishi Yukihide , Shirai Hiroaki
Published: April 2003

The one‐step synthesis of 2,6‐naphthalenedicarboxylic acid from naphthalene with carbon tetrachloride, copper powder and aqueous alkali has been achieved under mild conditions by the use of β‐cyclodextrin as catalyst, producing 2,6‐naphthalenedicarboxylic acid in 65 mol‐% yield with 79% selectivity.
Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 1. Initiation by ethyl α‐lithioisobutyrate
Authors: Novakov Christo P. , Tsvetanov Christo B.
Published: April 2003

The anionic polymerization of methyl methacrylate (MMA) was carried out in the presence of ethyl α‐lithioisobutyrate (α‐LiEtIB)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran/toluene (vol. ratio 75/25) at −60°C. It was found that the tacticity of PMMA strongly depends on size and shape of QAS. A highly isotactic polymerization in toluene was observed, when using the system α‐LiEtIB/trimethylhexadecylammonium bromide. The initiator system α‐LiEtIB/tetrahexylammonium chloride produces polymers with a high (>50%) syndiotactic content and relatively low polydispersity. The influence of QAS on the mode of polymerization is due to specific salt effect resulting from the cation exchange reaction, from the participation of the bulky substituent in the primary solvation shell, and ionic aggregation between the growing anion, Q+ and LiX.
New chitin‐based polymer hybrids, 1. Miscibility of poly(vinyl alcohol) with chitin derivatives
Authors: Aoi Keigo , Takasu Akinori , Okada Masahiko
Published: April 2003

As a new class of biopolymer‐based hybrid materials, the present paper describes the binary blends of a modified chitin and poly(vinyl alcohol) (PVA) which are miscible in the whole range of compositions. The blend films were prepared by the solvent cast method from a homogeneous aqueous solution of PVA and a chitin derivative having poly(2‐methyl‐2‐oxazoline) side chains. Miscibility between PVA and poly(2‐methyl‐2‐oxazoline) homopolymer was also revealed. Differential scanning calorimetry and FT‐IR analyses were used to investigate the blends.
Preparation and determination of the structure of high‐performance polymer blends by small‐angle neutron scattering
Authors: Caspar Jörg , Dünges Bastian , Kirste Rudolf G. , Heitz Thomas , Wiedenmann Albrecht
Published: April 2003

Amorphous blends from a deuterated polyaryletherketone and a polyetherimide have been prepared and investigated by neutron scattering. The used components differ remarkably in their structure and their solution properties. The blends on the other hand are combinatorial mixtures: the scattering quantity ϕ1ϕ2/S(q) is independent of the composition of the blends if the polymer chains have the same length.
Anionic polymerization of optically active oxiranes
Authors: Haubenstock Howard , Yu Wei‐Hong , Odian George
Published: April 2003

The anionic bulk polymerization of optically active (2R, 3S)‐3,4‐epoxy‐1,2‐O‐isopropylidenebutane‐1,2‐diol (1) and its (2 S, 3 S) diastereomer 2 was studied. Molecular weights and optical activity measurements as well as carbon and proton NMR spectra are reported. The polymers show solvent dependent inversion of the sign of optical rotation. The NMR spectra are consistent with isotactic polymer chains.
Changes in the sol‐gel transformation behavior of azobenzene moiety‐containing methylcellulose irradiated with UV light
Authors: Arai Kenichiro , Kawabata Yumi
Published: April 2003

Azobenzene moiety‐containing methylcellulose (AB‐MC) was prepared, the changes of the cloud point of its aqueous solutions as a thermotropic sol‐gel transformation behaviour were investigated under irradiation with UV light. AB‐MC's with degrees of substitution by the azobenzene moiety DSAB > 2,5 · 10‐2 were insoluble in water. The azobenzene moiety in the AB‐MC was confirmed to be reversibly isomerized from the trans‐ to the cis‐form under irradiation with UV light of wavelengths 390 > λ > 310 nm and from the cis‐to the trans‐form under irradiation with visible light of λ > 400 nm. The cloud point value of the aqueous solution of AB‐MC increased under irradiation with UV light of 390 > λ > 310 nm for the AB‐MC's with a DSAB value in a certain range and the extent of the increase in the cloud point value was higher at higher concentrations of AB‐MC.
Cationic ring‐opening polymerization of new 1,6‐anhydro‐β‐lactose derivatives
Authors: Yoshida Takashi , Yasuda Yuichi , Hattori Kazuyuki , Uryu Toshiyuki
Published: April 2003

Synthesis and cationic ring‐opening polymerization of new 1,6‐anhydro‐β‐lactose derivatives such as hexa‐O‐methylated (LSHME), tert‐butyldimethylsilylated (LSHSE), and benzylated 1,6‐anhydro‐β‐lactoses (LSHBE) were first investigated. The disaccharide monomers were prepared by methylation, tert‐butyldimethylsilylation, and benzylation of 1,6‐anhydro‐β‐lactose, respectively. It was found that LSHME was readily polymerized with such Lewis acid catalysts as PF5 and SbCl5 to give stereoregular 2,3‐di‐O‐methyl‐4‐O‐(2′,3′,4′,6′‐tetra‐O‐methyl‐β‐D‐galactopyranosyl)‐(1→6)‐β‐D‐glucopyranans which are comb‐shaped polysaccharide derivatives. However, LSHSE and LSHBE had almost no polymerizability. It was revealed that the ring‐opening polymerizability of the anhydrodisaccharide monomers was influenced by the steric hindrance of the hydroxyl‐protective groups. Ring‐opening copolymerization of LSHME with 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (LGTBE) in various ratios of monomer feeds was also examined to afford the corresponding copolymers. Structural analyses of the monomers and polymers were carried out by means of high resolution nuclear magnetic resonance spectroscopy.
A comparative dielectric study on the molecular dynamics of the liquid crystalline and the amorphous state of copolyesters
Authors: Ahumada Oscar , Ezquerra Tiberio A. , Nogales Aurora , Baltà‐Calleja Francisco J. , Zachmann Hans G.
Published: April 2003

The complex dielectric permittivity has been measured in the 103−106 Hz frequency range for selected random copolyesters of poly(ethylene terephthalate). The variation of the dielectric properties with temperature has been qualitatively related mainly to two processes. The α relaxation, which is associated with the glass transition, has been shown to be dependent on the molecular order of the systems. The β relaxation process has been assigned to local motions of the ester groups attached to both sides of the aromatic rings. The β process is also shown to exhibit a dependence on molecular order.
Influence of crosslinking conditions on the phase behavior of a polyacrylate‐based liquid‐crystalline elastomer
Authors: Zubarev Eugene R. , Talroze Raissa V. , Yuranova Tatyana I. , Vasilets Victor N. , Platé Nicolai A.
Published: April 2003

The influence of crosslinking conditions (γ‐radiation‐induced and chemical crosslinking above and below the clearing point) on the phase behavior of a liquid‐crystalline polyacrylate‐based elastomer is shown and discussed. The network formation in samples γ‐irradiated in the nematic phase results in an increase of the clearing point Tn‐i which does not depend on the crosslinking density expressed as the ratio of weight‐average molecular weight over number‐average molecular weight between crosslinks Mw/Mc within a wide Mw/Mc range. The distorting action of the crosslinking agent at the same temperature leads to the opposite tendency in the change of Tn‐i. Crosslinking in the isotropic phase shows a strong decrease in Tn‐i.
Uptake of silicone oil in the polystyrene matrix of the two phase system polystyrene/silicone oil as detected by NMR
Authors: Appel Mattias , Fleischer Gerald , Geschke Dieter , Kärger Jörg , Winkler Mario , Dieng Amadou C. , Riess Gérard
Published: April 2003

The decrease of the droplet radii of silicone oil dispersed in a polystyrene matrix at a temperature of 140°C with increasing time was measured by NMR dynamic imaging. From this time dependence the diffusion coefficient of the silicone oil into the matrix was calculated to be 7 · 10−18m2· s−1. The uptake of the silicone oil in the polystyrene matrix was confirmed by broad line NMR measurements.
Anionic graft copolymerization of methyl methacrylate with lithium diisopropylamide‐treated poly(methyl α‐substituted acrylate)s
Authors: Akutsu Fumihiko , Inoki Mari , Kasashima Yoshio , Shimajiri Yoichi , Naruchi Kiyoshi
Published: April 2003

The anionic grafting of methyl methacrylate onto several lithium diisopropylamide (LDA) — treated polymers of methyl α‐substituted acrylates containing an active methylene or methine group was investigated. The grafting was carried out using a mole ratio of LDA/acrylate unit of 0.75 in the feed polymer. The anionic graft copolymerizability of these acrylate polymers largely depends upon the surrounding of the active α‐hydrogen atom adjoining a carbonyl group or of the carbanion produced by the LDA treatment in the feed polymer.
Synthesis of α‐norbornenyl polystyrene macromonomers and their ring‐opening metathesis polymerization
Authors: Heroguez Valérie , Gnanou Yves , Fontanille Michel
Published: April 2003

Polystyrene macromonomers, fitted with a norbornenyl unsaturation in α position, have been obtained from a norbornene based carbanionic initiator that has been purposely designed to this end. The advantages of this synthetic scheme over that based on the deactivation of living PS chains are emphasized. One of the macromonomers prepared has been subsequently polymerized by ring‐opening metathesis, using a Schrock complex as initiator. The characterization of the resulting polymacromonomers showed that the metathesis process occurred under “living” conditions.
Bimodality in molar‐mass distribution in polystyrenes initiated by perchloric acid — an artifact? — not diagnostic of propagating species?
Authors: Pepper David Charles
Published: April 2003

Recently rediscovered evidence supports the conclusion that the bimodality of molarmass distributions in polystyrenes initiated by HCIO4 is not, as widely believed, the consequence of independent chain‐growth by different propagating species, but originates from lack of uniformity in reagent concentrations during the earliest stage of the polymerization, where the time‐scale of the growth and decay of the transient ionic population is short compared with that of mixing, in conventional preparative experiments.
A novel group transfer polymerization of 1‐trimethylsiloxy‐benzocyclobutene via hetero Diels‐Alder reaction
Authors: Chino Keisuke , Takata Toshikazu , Endo Takeshi
Published: April 2003

A novel group transfer polymerization via hetero‐Diels‐Alder reaction is described. When 1‐trimethylsiloxybenzocyclobutene (1) was treated with a catalytic amount of p‐anisaldehyde (4‐methoxybenzaldehyde) and TASF (tris(dimethylamino)sulfonium difluorotrimethylsilanide) at room temperature for 0.5 h, poly[1,2‐phenylene‐1‐(trimethylsiloxy)ethylene] was obtained quantitatively. The number‐average molecular weight of the polymer was M̄n = 2000 and the molecular weight distribution was narrow (ratio of weight‐to number‐average molecular weights M̄w/M̄n = 1.18). Structural characteristics suggested a polymerization mechanism involving isomerization of 1 to o‐quinodimethane and successive hetero‐Diels‐Alder reaction leading to poly[1,2‐phenylene‐1‐trimethylsiloxy ethylene]. The living‐like nature of the polymerization was supported by a monomer addition experiment in which the molecular weight increased according to the increase of the added monomer.
Synthesis of stereoregular poly[(2S,3S)‐benzyl β‐3‐methylmalate]
Authors: Mabille Christine , Masure Michèle , Hémery Patrick , Guérin Philippe
Published: April 2003

The asymmetric lactone (3 S, 4 R)‐3‐methyl‐4‐benzyloxycarbonyl‐2‐oxetanone (6) was anionically polymerized to give an insoluble, crystalline, highly isotactic polymer with (2 S, 3 S)‐benzyl β‐3‐methylmalate repeating units. Solubility was achieved by copolymerization of 6 with the recemic (R, S)‐butyl malolactonate (7). The semicrystalline copolymer was characterized (M̄n = 107 000, Tg = 29,6°C, Tm = 161°C, [α] = 1,5 deg · dm−1 · g−1 · cm3) and its stereosequence investigated by 13C NMR.
Novel sub‐ceiling temperature rapid depolymerization‐repolymerization reactions of cyanoacrylate polymers
Authors: Ryan Bernard , McCann Gerard
Published: April 2003

Dilute solutions of unimodal high‐molecular‐weight poly(butyl cyanoacrylate) (“parent” polymer) in tetrahydrofuran (THF) at 21°C underwent rapid depolymerization accompanied by simultaneous repolymerization of the unzipped monomer to yield lower‐molecular‐weight “daughter” polymer following addition of tetrabutylammonium hydroxide (TBAOH), a slow initiator of butyl cyanoacrylate (BCA) monomer. The rate‐determining step for the reaction was tentatively identified as abstraction of the terminal chain proton. Similarly, addition of TBAOH to a THF solution of BCA monomer resulted in initial formation of high‐molecular‐weight (MW) polymer that subsequently rapidly depolymerized with simultaneous formation of TBAOH initiated, low‐MW daughter polymer. The depolymerization‐repolymerization reaction is the relaxation process that occurs following perturbation of the monomer/high‐MW parent polymer equilibrium by low‐MW daughter polymer and proceeds at least 100°C below the ceiling temperature of the parent polymer.
Effect of polymerization of synthetic glycolipids on their supramolecular assemblies
Authors: Polidori Ange , Pucci Bernard , Zarif Leila , Riess Jean G. , Pavia André A.
Published: April 2003

Sugar‐derived surfactants bearing a polymerizable acryloyl moiety on one of the branches of the double‐chain hydrophobic tail were prepared. The non–ionic hydrophilic head and the biantennary hydrophobic tail were built on, respectively, an aspartic acid and a tris(hydroxymethyl)aminomethane core. Ultraviolet irradiation of aqueous dispersions of these surfactants above their transition phase temperature (Tc) was achieved. The morphology of self‐assemblies produced in such a way were investigated by transmission electron microscopy. TEM photographs revealed that irradiation leads to the formation of unilamellar vesicles. Neither fibers nor tubules were detected in contrast to what was observed before polymerization.
New simple procedures for the prediction of monomer reactivity ratios and transfer constants in radical polymerisation
Authors: Jenkins Aubrey D.
Published: April 2003

The Q‐e and Patterns of Reactivity schemes for the quantitative treatment of the reactions of polymer radicals both suffer from drawbacks which seriously limit their usefulness. Two revised versions of the Patterns of Reactivity scheme, in which all the necessary parameters are derived from experimental data, are summarised here. Both new schemes provide significantly more accurate assessments of monomer reactivity ratios and transfer constants than do their predecessors.
Transition metal‐catalyzed ring‐opening copolymerization of silicon‐bridged [1]ferrocenophanes and sila‐ or disilacyclobutanes: Synthesis of poly(ferrocenylsilane)‐poly(carbosilane) random copolymers
Authors: Sheridan John B. , Elipe Paloma Gómez , Manners Ian
Published: April 2003

The first examples of poly(ferrocenylsilane)‐poly(carbosilane) random copolymers have been prepared via the transition metal‐catalyzed ring‐opening copolymerization of silicon‐bridged [1]ferrocenophanes and disila‐ or benzosilacyclobutane.
Polymerization and copolymerization of ethene initiated with disiloxane‐bridged biscyclopentadienylzirconium complexes and methylaluminoxane
Authors: Lee Dong‐ho , Yoon Keun‐byung , Lee Eok‐hyung , Noh Seok‐kyun , Lee Chul‐soo , Huh Wan‐soo
Published: April 2003

The disiloxane‐bridged zirconocene complexes, tetramethyldisiloxanediylbis (cyclopentadienyl)zirconium dichloride and tetramethyldisiloxanediylbis(cyclopentadienyl) dimethylzirconium initiate the homopolymerization of ethene as well as the copolymerization of ethene and α‐olefin with a modified methylaluminoxane as cocatalyst. The catalyst systems give resonable activity but the molecular weight of polyethene decreases drastically with increasing polymerization temperature.
Controlled radical polymerization of styrene in the presence of nitronyl nitroxides
Authors: Shigemoto Takeo , Matyjaszewski Krzysztof
Published: April 2003

Bulk radical polymerization of styrene in the presence of nitronyl nitroxides (2‐(4‐substituted phenyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydroimidazolyl‐1‐oxyl 3‐oxide) was studied. All nitronyl nitroxides, like other nitroxyl radicals such as 2,2,6,6‐tetramethylpiperidine 1‐oxyl radical (TEMPO), act as reversible radical scavengers. The efficiency of controlling the polymerization is affected by the substituent at the 4′‐position. The efficiency increases with electron donating strength of 4′‐substituents, at least at the beginning of the reaction. However, the thermal stability of nitronyl nitroxides decreases in the same order. Thus, TEMPO is more suitable than nitronyl nitroxides for controlled/“living” radical polymerization of styrene.
Polymerization of N‐phenylmaleimide with rare earth coordination catalysts
Authors: Jiang Liming , Zhang Yifeng , Shen Zhiquan , Shen Lianfang , Yuan Hanzhen
Published: April 2003

A highly active rare earth coordination catalyst composed of neodymium acetylacetonate, dibutylmagnesium, and hexamethylphosphoramide (mole ratio 1:7:14) for the polymerization of N‐phenylmaleimide (N‐PMI) was developed. The resulting poly(N‐PMI) has high molecular weight (M̄n = 9.0 × 104) and shows excellent thermal stability.
Effect of a π‐donor on the radical bulk polymerization of methyl methacrylate
Authors: Wunderlich Wiebke , Benfaremo Nick , Klapper Markus , Müllen Klaus
Published: April 2003

Bulk polymerizations of methyl methacrylate (MMA) at 60°C initiated with 2,2′‐azoisobutyronitrile are influenced by the presence of an organic π‐donor such as tetrathiafulvalene (TTF). Upon addition of TTF, the ratio of weight‐ to number‐average molecular weights M̄w/M̄n are significantly reduced and the thermal stability of the poly(methyl methacrylate) samples is increased. Kinetic investigations indicate that TTF acts as a retarder on the polymerization mechanism.
Liquid‐crystalline structure of poly(L‐lysine) containing azobenzene units in the side chain
Authors: Gallot Bernard , Fafiotte Marc , Fissi Adriano , Pieroni Osvaldo
Published: April 2003

The structure of poly(L‐lysine) containing 44% azobenzene units in the side chain was studied by X‐ray diffraction between room temperature and 150°C. The polymer exhibits a mesomorphic structure of the smectic A1 type. In this structure, stable at least until 150°C, each smectic layer of thickness d results from the superposition of two layers: one of thickness dA contains the free lysine side chains, the other of thickness dB contains the azobenzene modified lysine side chains and the polypeptide main chains, that in their planes are arranged as in the “antiparallel” β‐structure classical for polypeptides.
Shape memory behaviors of crosslinked copolymers containing stearyl acrylate
Authors: Kagami Yoshiharu , Gong Jian Ping , Osada Yoshihito
Published: April 2003

Shape memory polymers were prepared by copolymerizing stearyl acrylate and methyl acrylate. The principle of this shape memory effect is based on reversible order‐disorder transition of crystalline aggregates of stearyl moieties. A specific feature of this type of shape memory copolymer is that the transition temperature at which the polymer abruptly becomes soft and deforms can be controlled by changing the monomer composition, which enables one to adjust the shape memory effect at a desired temperature. Mechanism and process of the shape memory behaviors were discussed.
Enzymes in polymer chemistry, 9. Polymerizable oligoesters from cholic acid via lipase catalyzed condensation reactions
Authors: Noll Olaf , Ritter Helmut
Published: April 2003

Regioselective oligocondensation of cholic acid in the 3‐position was achieved in organic solution in the presence of a lipase from Candida antarctica. Furthermore, a mixture of cholic acid, 11‐methacryloylaminoundecanoic acid and the lipase resulted in the production of a radically polymerizable oligo(cholic acid ester) bearing exactly one methacrylic end group. This new monomer was polymerized radically yielding the corresponding comb‐polymers bearing several cholic acid esters at the end of the side chains.
Ultrahigh molecular weight alternating propene/ethene/carbon monoxide terpolymers with elastic properties
Authors: Abu‐Surrah Adnan S. , Eckert Gabriele , Pechhold Wolfgang , Wilke Wolfgang , Rieger Bernhard
Published: April 2003

Soluble propene/ethene/CO terpolymers (EPEC) with ultrahigh molecular weight (up to 1.2 × 106 g/mol) were prepared by the use of dicationic palladium(II) phosphine catalysts and an optimized amount of water as activator. When the molar ratio of ethene/CO to propene/CO is below 50 mol‐%, the terpolymers are thermoplastic elastomers with excellent properties. Above this ratio the terpolymers are crystalline thermoplastics. The ultrahigh molecular weight elastomers are highly soluble in organic solvents such as CH2Cl2 and CHCl3.
Evolution of the “knitting pattern” morphology in ABC triblock copolymers
Authors: Breiner Ulrike , Krappe Udo , Stadler Reimund
Published: April 2003

A new morphology of ternary ABC triblock copolymers is presented which results from the asymmetric interaction between a centre block (poly(ethylene‐co‐butene)) to different end blocks (polystyrene and poly(methyl methacrylate)). This morphology with the appearance of a “knitting pattern” can be described as an intermediate of a morphology of A, B and C lamellae and a morphology of A and C lamellae with B cylinders at the A/C interface.
Polymerization of 3‐methyl‐1‐butene promoted by metallocene catalysts
Authors: Borriello Anna , Busico Vincenzo , Cipullo Roberta , Chadwick John C. , Sudmeijer Olof
Published: April 2003

3‐Methyl‐1‐butene was polymerized in the presence of a number of homogeneous metallocene catalysts (co‐catalyst methylalumoxane). Contrary to literature reports, it was found that even the simplest C2‐symmetric metallocenes promote the isotactic polymerization of this monomer with reasonable productivities. Quite surprisingly, a prevailingly isotactic polymer was also obtained in the presence of Cs‐symmetric metallocenes, which are instead syndiotactic‐specific in propene polymerization.
Determination of reactivity ratios for ethylene/α‐olefin copolymerization catalysed by the C2H4[Ind]2ZrCl2/methylaluminoxane system
Authors: Galland Griselda Barrera , Quijada Paul , Mauler Raquel Santos , de Menezes Sônia C.
Published: April 2003

The present study reports values of reactivity ratios for ethylene/1‐hexene, ethylene/1‐octene and ethylene/1‐decene copolymerizations promoted by C2H4[Ind]2ZrCl2/MAO. The comonomer reactivities are markedly influenced by the number of carbon atoms of the α‐olefin. The ethylene/1‐decene copolymerization depends on the concentration of α‐olefin in the feed.
Miscibility in a ternary system of poly(ether imide) with semicrystalline poly(ethylene terephthalate) and poly(butylene terephthalate)
Authors: Yau Shang N. , Woo Eamor M.
Published: April 2003

A rare case of thermodynamic miscibility has been demonstrated in the amorphous state (quenched glass as well as molten state) of a ternary blend system formed by poly(ether imide) and semicrystalline poly(ethylene terephthalate) and poly‐(butylene terephthalate). A single glass transition temperature (Tg) in the ternary blends was observed using differential scanning calorimetry and dynamic mechanical analysis.
Dendrimers with 1,3,4‐oxadiazole units, 1. Synthesis and characterization
Authors: Bettenhausen Jörg , Strohriegl Peter
Published: April 2003

The synthesis and characterization of two unsymmetrically substituted star‐shaped oxadiazoles and of a dendrimer of the first generation are described. The key step in the synthesis is the intramolecular ring transformation of aromatic tetrazoles. The well‐defined compounds form stable amorphous glasses with high glass transition temperatures up to 222°C. They are promising candidates for organic light emitting diodes.
Polymerization of ethene initiated with a mixture of siloxane‐bridged mono‐ and dinuclear zirconocenes
Authors: Lee Dong‐ho , Yoon Keun‐byoung , Noh Seok‐kyun , Kim Su‐chan , Huh Wan‐soo
Published: April 2003

In the polymerization of ethene cocatalyzed with modified methylaluminoxane, the catalyst activities of the siloxane‐bridged dinuclear zirconocenes, tetramethyldisiloxanediylbis(cyclopentadienylindenylzirconium dichloride) (3) and hexamethyltrisiloxanediylbis(cyclopentadienylindenylzirconium dichloride) (4) were lower than that obtained with the siloxane‐bridged mononuclear zirconocene, tetramethyldisiloxanediyldicyclopentadienyldimethylzirconium (1). On the other hand, weight‐average molecular weight M̄w and ratio of weight‐ to number‐average molecular weights M̄w/M̄n of polyethene (PE) obtained with 3 or 4 were higher than those of PE obtained with 1. For a binary mixture of 1/3 or 1/4, it was found that the obtained PE exhibits a bimodal molecular weight distribution for an appropriate composition of the mixed zirconocenes. M̄w/M̄n of PE could be adjusted by changing the relative concentrations of the two zirconocenes.
Living free radical donor‐acceptor copolymerization of styrene and N‐cyclohexylmaleimide and the synthesis of poly[styrene‐co‐(N‐cyclohexylmaleimide)]/polystyrene block copolymers
Authors: Schmidt‐Naake Gudrun , Butz Sören
Published: April 2003

Styrene/N‐cyclohexylmaleimide copolymers with small polydispersities and controlled molecular weights were synthesized by a free radical copolymerization using an iniferter system consisting of benzoyl peroxide and 2,2,6,6‐tetramethylpiperidine‐N‐oxyl. Due to the interactions of the electropositive (styrene) and electronegative (N‐cyclohexylmaleimide) monomers the brutto polymerization rates are higher than for other living polymerizations initiated with the same iniferter system. The prepared copolymers were used as macroiniferters for bulk polymerization of styrene.
“Living radical” polymerization of styrene in the presence of a nitroxide compound
Authors: Hammouch Saíd Oulad , Catala Jean‐Marie
Published: April 2003

The influence of parameters such as styrene dilution and active site concentration on the polymerization of styrene in the presence of a di‐tert‐butyl nitroxide adduct (A‐T) was examined. It is confirmed that the rate of styrene polymerization is independent of A‐T concentration, with no monomer dilution effect. An increase in radical concentration generated in the medium leads to faster propagation, but the molecular weight of the polymers formed is alway controlled by the A‐T concentration.
Synthesis of a functional polymer with pendent luminescent phenylenevinylene units through nitroxide‐mediated free‐radical polymerization
Authors: Moroni Marc , Hilberer Alain , Hadziioannou Georges
Published: April 2003

In this communication we report the synthesis and the efficient polymerization of a PPV trimer, 4‐tert‐buty1‐4′‐(4‐vinylstyryl)‐trans‐stilbene. By using the TEMPO (2,2,6,6‐tetramethylpiperidin‐1‐yloxy)‐mediated free‐radical polymerization method, the corresponding polymer was obtained in high yields, with a fair molecular weight and a small polydispersity. The presence of phenylenevinylene units in the side chains of the polymer gives rise to efficient blue fluorescence which makes the material suitable for light emission applications.
Cyclodextrin sidechain polyesters — synthesis and inclusion of adamantan derivatives
Authors: Weickenmeier Meik , Wenz Gerhard
Published: April 2003

An efficient synthesis of a cyclodextrin polymer by a polymer‐analogous reaction of lithium β‐cyclodextrinate with poly[(N‐vinyl‐2‐pyrrolidinone)‐co‐(maleic anhydride)] is described. Because cyclodextrin polymer is highly water‐soluble, its binding of guests, like 1‐adamantanamine and l‐adamantanecarboxylic acid, could be investigated by titration microcalorimetry. All cyclodextrin moieties are accessible by the guest within the polymer, but binding constants are slightly lower than those for native β‐cyclodextrin. Binding constants are influenced by Coulomb interactions between the guest and the anionic polymer backbone.
Synthesis of comb‐like polyurethanes containing hydrophilic phosphatidylcholine analogues in the main chains and hydrophobic long chain alkyl groups in the side chains
Authors: Li Yu‐Jun , Nakamura Naotoshi , Chen Tian‐Ming , Wang Yan‐Feng , Kitamura Masaya , Nakaya Tadao
Published: April 2003

Three new amphiphilic phospholipid diols containing hydrophilic phosphatidylcholine analogues in the main chains and hydrophobic octadecyl, hexadecyl or dodecyl alkyl groups in the side chains were synthesized. The typical phospholipid diol based on an octadecyl group was further reacted with diisocyanates such as hexamethylene diisocyanate (HDI), 2,4‐tolylene diisocyanate (TDI) and 4,4′‐methylenediphenyl diisocyanate (MDI), respectively. Preliminary studies suggest that polyurethane based on MDI shows a viscosity behavior similar to common polyelectrolytes and exhibits a therm decomposition peak at 244°C due to the phospholipid moiety and a melting point at 218°C.