bluuebunny/crossref_metadata_2025_split huggingface dataset:
New chitin‐based polymer hybrids, 1. Miscibility of poly(vinyl alcohol) with chitin derivatives
Authors: Aoi Keigo , Takasu Akinori , Okada Masahiko 
Published: April 2003

AbstractAs 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

AbstractAmorphous 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

AbstractThe 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

AbstractAzobenzene 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

AbstractSynthesis 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractPolystyrene 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

AbstractRecently 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

AbstractA 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

AbstractThe 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

AbstractDilute 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

AbstractSugar‐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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractBulk 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

AbstractA 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

AbstractBulk 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

AbstractThe 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

AbstractShape 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

AbstractRegioselective 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

AbstractSoluble 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

AbstractA 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

Abstract3‐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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractIn 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.