bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymerization of cyclic monomers, 1. Radical polymerization of unsaturated spiro orthocarbonates
Authors: Moszner Norbert , Zeuner Frank , Rheinberger Volker 
Published: April 2003

Abstract7‐Methyl‐2‐methylene‐ (1) and 7‐methyl‐2,3‐dimethylene‐1,4,6,9‐tetraoxaspiro[4.4]nonane (2) were synthesized and characterized by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. Radical polymerization of the spiro orthocarbonates (SOC) 1 and 2 show that they undergo primarily vinyl polymerization with a low degree of ring‐opening reaction. Homopolymerization of 2 at 120°C with di‐tert‐butyl peroxide gives a transparent crosslinked polymer and the polymerization generates a 12,5% shrinkage in volume.
Strain‐induced director reorientation in nematic liquid single crystal elastomers
Authors: Kundler Isabel , Finkelmann Heino 
Published: April 2003

AbstractThe strain‐induced director reorientation process in nematic liquid single crystal elastomers is investigated for the case of an arbitrary angle between the original director and the external stress axis. If the mechanical stress is applied perpendicular to the original director axis, the reorientation process sets in at a threshold strain. The mesogens are realigning ‘clockwise’ or ‘counter‐clockwise’ towards the axis of external stress, simultaniously the monodomain structure is distorted and a periodic pattern formation is observed. If the mechanical stress is applied obliquely with respect to the original director axis, a uniform director reorientation is obtained with retention of the monodomain structure. No threshold strain is observed for this process. The existence of a threshold strain in the case of a perpendicular arrangement of the director to the external stress axis can be understood as a consequence of the distortion of the monodomain structure.
Control of photochemistry of stilbazolium ion by adsorption to poly(potassium vinylsulfate) and to hectorite clay
Authors: Nakahira Takayuki , Hama Masayuki , Fukuchi Osamu , Okamura Toshiya , Iwabuchi Susumu , Shimazu Shogo , Uematsu Takayoshi , Kikuchi Hideo 
Published: April 2003

AbstractAdsorption or intercalation of trans‐1‐methyl‐4‐(2‐phenylvinyl)pyridinium ion (stilbazolium ion, SB (1)) to a polyelectrolyte, i. e., poly(potassium vinylsulfate) (PVSK), and to a hectorite clay is studied and its effect on the photochemistry of SB examined. trans‐cis Photoisomerization of SB molecularly adsorbed to PVSK proceeds efficiently as with free SB in water, while that of SB molecularly intercalated in the clay is markedly suppressed. Photodimerization proceeds efficiently with SB intercalated in the clay in the aggregated form. Overall photodecoloration, however, proceeds more efficiently with SB adsorbed to PVSK under multiple adsorption conditions apparently due to the higher mobility of PVSK‐adsorbed SB compared to that of clay‐intercalated SB.
Dielectric properties of a hydrogen‐bonded liquid‐crystalline side‐chain polymer
Authors: Araki Kazuo , Kato Takashi , Kumar Uday , Fréchet Jean M. J. 
Published: April 2003

AbstractThe dielectric properties of a hydrogen‐bonded side‐chain liquid‐crystalline polysiloxane have been examined over wide ranges of frequency and temperature. This polymer has a side‐chain mesogenic moiety consisting of a benzoic acid and a stilbazole. The observed dielectric loss curves contain a component from dipole reorientation of the hydrogen‐bonded mesogenic group. It has been found to be possible that, using electrical and thermal treatments, such a polymer built through hydrogen bonding can align homeotropically.
Synthesis of novel glycopeptide‐polyoxazoline block copolymers by direct coupling between living anionic and cationic polymerization systems
Authors: Tsutsumiuchi Kaname , Aoi Keigo , Okada Masahiko 
Published: April 2003

AbstractA novel glycopeptide‐containing block copolymer, poly[O‐(tetra‐O‐acetyl‐β‐D‐glucopyranosyl)‐L‐serine]‐block‐poly(2‐methyl‐2‐oxazoline) (5), was synthesized by mutual termination of living polymerizations of a sugar‐substituted α‐amino acid N‐carboxyanhydride (NCA) (1) and 2‐methyl‐2‐oxazoline (3). 5 was deacetylated to provide the glycopeptide‐polyoxazoline block copolymer, poly[O‐(β‐D‐glucopyranosyl)‐L‐serine]‐block‐poly(2‐methyl‐2‐oxazoline) (6).
Miscible blends containing a crystallizable component: poly(vinyl alcohol)/poly(ethyleneimine)
Authors: Guo Qipeng 
Published: April 2003

AbstractBlends of poly(vinyl alcohol) (PVAI) with poly(ethyleneimine) (PEI) were prepared by casting from a common solvent. All blends show a single, composition dependent glass transition temperature (Tg), indicating that the blends are miscible in the amorphous state and in the melt. The overall crystallization rate of PVAI in the blend decreases with increasing PEI content. The crystallinity index of PVAI in the blend does not decrease greatly with PEI content up to a composition of 70/30 PVAI/PEI, since the Tg of the crystallizable component PVAI is larger than that of the non‐crystallizable component PEI. The Tg of the system PVAI/PEI decreases with increasing PEI content. The interaction parameter B of the two polymers in the melt was found to be −24 J/cm3.
A metallocene catalyst system for olefin polymerization using a heteropolyacid as the counter‐anion
Authors: Soga Kazo , Uozumi Toshiya , Kishi Naoya 
Published: April 2003

AbstractPolymerization of ethylene and propene were conducted with bis(cyclopentadienylzirconium dichloride) (Cp2ZrCl2) and ethylenebis(1‐indenyl)zirconium dichloride (Et(Ind)2ZrCl2) combined with trialkylaluminium compounds using heteropolyacids as the counter‐anions, giving linear polyethylene and isotactic polypropene, respectively. No polymer was obtained when using Cp2Zr(CH3)2 instead of Cp2ZrCl2. The mechanism of the formation of active species is briefly discussed on the basis of these results.
X‐ray photoelectron spectroscopic study of poly[4,4′‐isopropylidenebis(1,4‐phenyleneoxyethylene) diacrylate] photocured in the presence of a fluorine containing monomer
Authors: Pollicino Antonino , Siracusa Valentina , Bongiovanni Roberta , Priola Aldo 
Published: April 2003

AbstractA preliminary X‐ray photoelectron spectroscopic (XPS) investigation on poly[4,4′‐isopropylidenebis(1,4‐phenyleneoxyethylene) diacrylate] samples obtained by photocuring on several substrates in the presence of a fluorine containing acrylic monomer is reported. Quantitative calculations based on F1s/C1s area ratios and C1s peak fitting show a noticeable fluorine surface enrichment that ranges, depending on the substrate, from 17 wt.‐% to 59 wt.‐% of fluorine containing moiety. The calculations also reveal the presence of a concentration gradient at the surface.
A latent entanglement model for the draw of semicrystalline polymers
Authors: Ottani Stefano , Porter Roger S. 
Published: April 2003

AbstractA novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.
Polystyrene‐supported metallocene catalysts for olefin polymerizations
Authors: Nishida Hiroto , Uozumi Toshiya , Arai Takashi , Soga Kazuo 
Published: April 2003

AbstractSeveral kinds of polystyrene‐supported metallocene catalysts were prepared and used in the polymerizations of propylene and ethylene with methylaluminoxane (MAO) as cocatalyst. It was found that these catalysts are stable even at 70°C. They display fairly high activities when the polymerizations are conducted at high temperatures.
Temperature‐responsive swelling and deswelling of the copolymers from vinyl ether of ethylene glycol and butyl vinyl ether
Authors: Kudaibergenov Sarkyt E. , Nurkeeva Zauresh S. , Mun Grigorii A. , Ermukhambetova Bayana B. , Nam Irina K. 
Published: April 2003

AbstractLinear and crosslinked copolymers of a vinyl ether of ethylene glycol (2‐hydroxyethyl vinyl ether, (1)) and butyl vinyl ether (2) are synthesized by α‐irradiation polymerization. It is shown that the linear copolymers exhibit a phase separation phenomenon in dependence of the temperature due to the destruction of hydrogen bonds and the enhancement of hydrophobic interaction in aqueous solution. The processes of reversible swelling or shrinking upon temperature change are demonstrated for polymer networks.
Non‐ionic surfactant effects on polymer diffusion in poly(butyl methacrylate) latex films
Authors: Kawaguchi Seigou , Odrobina Ewa , Winnik Mitchell A. 
Published: April 2003

AbstractThe influence of non‐ionic surfactant molecules on polymer interdiffusion in poly(butyl methacrylate) (PBMA) latex films was investigated using the non‐radiative energy transfer technique. It was found that nonylphenoxypoly(ethylene oxide) surfactants such as NP‐20 and NP‐100 act as plasticizers to enhance the polymer diffusion rate. The increase in diffusion rate with the increase in surfactant concentration is in complete accord with the Fujita‐Doolittle free volume model. This suggests that by the time the latex dispersion is dry, the surfactant has diffused uniformly into the latex polymer.
Synthesis of poly(L‐lactide)‐block‐polyisobutylene‐block‐poly(L‐lactide), a new biodegradable thermoplastic elastomer
Authors: Sipos László , Zsuga Miklós , Deák György 
Published: April 2003

AbstractThe anionic ring‐opening polymerization of L‐lactide was initiated by dipotassium‐poly‐isobutylene‐alcoholate telechelic polymer to yield poly(L‐lactide)‐block‐polyisobutylene‐block‐poly(L‐lactide) triblock copolymer, a partially biodegradable thermoplastic elastomer. The pure triblock copolymer was obtained by gradient column chromatography on silica gel. The molar mass and molar mass distribution of the block copolymer was ascertained by SEC and quantitative 1H NMR spectroscopy. It showed two glass transitions and microphase separation.
Study on the sorption of water into epoxy resins by means of electrochemical impedance spectroscopy
Authors: Luo Xiao‐Wen , Yun Ze‐Yong , Li Shan‐Jun , Zhou Wei‐Fang 
Published: April 2003

AbstractIn this work the relationship between structure and water sorption for epoxy films was studied using electrochemical impedance spectroscopy. It is shown that the electrochemical impedance spectroscopy can be applied to obtain information about the amount of water absorbed by the epoxy film and the water permeation through the film, while only the amount of water absorbed is obtained from the “sorption method”. The free volume is the decisive factor for both the amount of water in the cured epoxy film and water permeation through the film.
Lanthanoid isopropoxide as a novel initiator for anionic polymerization of isocyanates
Authors: Fukuwatari Naoko , Sugimoto Hiroshi , Inoue Shohei 
Published: April 2003

AbstractLanthanum isopropoxide was found to serve as a novel anionic initiator for the polymerization of hexyl isocyanate affording poly(hexyl isocyanate) with very high molecular weight (Mn > 106) under appropriate conditions. Other lanthanoid alkoxides, such as samarium, ytterbium and yttrium isopropoxides, also brought about the polymerization of hexyl isocyanate. Butyl, isobutyl, octyl and m‐tolyl isocyanates also underwent the polymerization reaction to form the corresponding polymers by using lanthanum isopropoxide as initiator, while polymerizations of tert‐butyl and cyclohexyl isocyanates with lanthanum isopropoxide did not occur under identical conditions.
Inversion of stereoselectivity in a metallocene catalyst
Authors: Shiomura Tetsunosuke , Asanuma Tadashi , Inoue Norihide 
Published: April 2003

AbstractInversion of stereoselectivity of a particular metallocene (Me2Si(Flu) (N‐t‐Bu)ZrCl2) (Me: methyl, Flu: fluorenyl, t‐Bu: tert‐butyl) from syndiospecific into isospecific was observed by changing the cocatalyst from methylaluminoxane (MAO) to [Ph3C]+ [B(C6F5)4]−/AliBu3 (iBu:isobutyl). The change of the solvent‐separated ion pair (in case of MAO as cocatalyst) into the contact ion pair (in case of the more polar and less bulky borate anion) was proposed as the plausible explanation of this phenomenon.
Synthesis of adjustable poly(vinyl chloride) networks
Authors: Reinecke Helmut , Hidalgo Manuel , Mijangos Carmen 
Published: April 2003

Abstract2‐Mercaptobenzyl alcohol and 4‐mercaptobenzyl alcohol were synthesized in good yields starting form thiosalicylic acid and p‐toluenesulfonic acid, respectively. Poly(vinyl chloride) (PVC) reacts selectively with the thiol group of these bifunctional compounds leading to modified PVC with free hydroxy groups. In a second step the polymer chains can be partially crosslinked by reaction with hexamethylene diisocyanate. According to the degree of PVC modification, the network density of the resulting elastomers is freely adjustable.
Characterization of pyrene end‐labeled poly(ethylene glycol) by high resolution MALDI time‐of‐flight mass spectrometry
Authors: Whittal Randy M. , Li Liang , Lee Sam , Winnik Mitchell A. 
Published: April 2003

AbstractWe report the characterization of a sample of poly(ethylene glycol) (PEG, Mn = 3841, Mw/Mn = 1.01), and its derivative end‐labeled with pyrenebutyrate groups, using high resolution MALDI time‐of‐flight mass spectrometry. A matrix of 2‐(4‐hydroxyphenyl‐azo)benzoic acid containing a trace of either sodium chloride or potassium chloride was employed for laser desorption. Peaks due to the sodium or potassium cationized polymers were obtained, equally spaced at 44 mass units apart. For the pyrenebutyrate diester, the analysis shows that 80 ± 2% of the chains were doubly labeled, with the ramaining chains containing only a single pyrene group. Molecular weight determinations for both sets of samples were entirely consistent with size‐exclusion chromatography measurements, but were obtained with greater accuracy and less ambiguity about the influence of the end groups on the hydrodynamic radius of the polymer.
Molecular imprinting of the endogenous neuropeptide Leu5‐enkephalin and some derivatives thereof
Authors: Andersson Lars I. , Müller Ralf , Mosbach Klaus 
Published: April 2003

AbstractWe have undertaken the molecular imprinting of Leu5‐enkephalin, and derivatives related to this endogenous neuropeptide, in highly cross‐linked methacrylic acid/ethylene dimethacrylate copolymers. The underivatized enkephalin peptide yielded polymers with poor recognition abilities, since the imprinting of this compound had to be performed using dimethyl sulfoxide, which was found to interfere with the imprint inducement, as the solvent of polymerisation. In order to circumvent this problem, the amino‐ and carboxy‐protected derivatives Boc‐Leu5‐enkephalin and Leu5‐enkephalin anilide, which are soluble in apolar solvents, were investigated as alternative imprint molecules. Both compounds led to polymers which are highly specific for the imprint species. The anilide derivative was shown to be a good substitute for the free peptide since the resultant polymers showed efficient recognition of the parent enkephalin structure.
Study of the thermal degradability of poly(α‐methylstyrene) with modified end groups
Authors: Nagasaki Yukio , Yamazaki Noriyuki , Kato Masao 
Published: April 2003

AbstractTo induce degradabilities in polymers in response to environmental conditions, endm odification reactions of poly(α‐methylstyrene) (PMS) derivatives were carried out. 2‐Phenylallyl halide derivatives such as 2‐phenylallyl bromide, 2‐(p‐tolyl)allyl bromide, and α‐trifluoromethylstyrene were found to be suitable end‐modification agents. For example, the ω‐2‐phenylallyl‐PMS derivative was prepared with almost quantitative functionality by the reaction of the living PMS derivative with 2‐phenylallyl bromide. In a similar way, ω‐3,3‐difluoro‐2‐phenylallyl‐ and ω‐2‐(4‐toly)allyl‐PMS derivatives were synthesized. Based on thermogravimetric analysis, the onset of the degradation temperature of the endmodified PMS derivatives decreased in the following order: ω‐hydrogen‐ > ω‐3,3‐difluoro‐2‐phenylallyl‐ > ω‐2‐phenylallyl‐ > ω‐2‐(p‐tolyl)allyl‐PMS. Actually, the onset temperature of ω‐2‐(p‐tolyl)allyl‐PMS derivatives was 50°C lower than that of ω‐H‐PMS derivatives. These results indicate that the active species is produced effectively at the endunsaturated bond, which initiates depolymerization of the polymer at rather low temperatures. Therefore, it is concluded that a 2‐phenylallyl substituent at the end of the PMS chain induces effective degradation through a radical mechanism.
Anionic polymerization of oxirane in the presence of the polyiminophosphazene base t‐Bu‐P4
Authors: Eßwein Beate , Steidl Norbert M. , Möller Martin 
Published: April 2003

AbstractThe use of the polyiminophosphazene base t‐Bu‐P4 (1) for the anionic polymerization of ethylene oxide is described. Polymerization initiated by a monoalkoxide of the protonated base leads to well‐defined poly(ethylene oxide)s with low polydispersity (Mw/Mn ≈ 1.1). Furthermore, graft copolymers of poly[ethylene‐co‐(vinyl alcohol)] (PEVA) with poly(ethylene oxide) and a star macromolecule were synthesized from multifunctional polyalkoxides in high yields.
Ion‐selective gel that is sensitive to temperature, pH, and redox reactions
Authors: Bromberg Lev , Levin Gideon 
Published: April 2003

AbstractIn this communication we describe ion‐selective poly[N,N‐diethylacrylamide‐co‐(2‐hydroxyethyl methacrylate)] gels functionalized by dialkyldithiophosphate group due to ester exchange reaction with the HEMA moieties. The gels are sensitive to temperature and pH in the surrounding aqueous solutions. Redox reactions cause gels to shrink due to crosslinking via disulfide bond formation.
(η3‐allyl)palladium(II) catalysts for the addition polymerization of norbornene derivatives with functional groups
Authors: Reinmuth Annette , Mathew Joice P. , Melia Jennifer , Risse Wilhelm 
Published: April 2003

AbstractCycloaliphatic polyolefins with functional groups were prepared by the Pd(II)‐catalyzed addition polymerization of norbornene derivatives. Homo‐ and copolymers containing repeating units based on bicyclo[2.2.1] hept‐5‐en‐2‐ylmethyl decanoate (endo/exo‐ratio = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept‐5‐ene‐2‐methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid (100% endo) were prepared in 49–99% yields with {(η3‐allyl)Pd(BF4)} and {(η3‐allyl)Pd(SbF6)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd‐complex.
Effect of tetraalkylammonium salts on the tacticity of poly(methyl methacrylate), 2.. Initiation by potassium tert‐butoxide
Authors: Novakov Christo P. , Tsvetanov Christo B. 
Published: April 2003

AbstractThe anionic polymerization of methyl methacrylate was carried out in the presence of potassium tert‐butoxide (t‐BuOK)/quaternary ammonium salts (QAS) in toluene and tetrahydrofuran at −60°C. It was found that in toluene some QAS additives substantially increase the syndiotacticity of poly(methyl methacrylate). Two types of QAS were distinguished, quite different in their action. The addition of QAS with one or two longchain alkyl groups (>C12), does not change significantly the mode of the monomer addition, whereas the polymerization in the presence of tetraalkylammonium salts with four equal substituents and dimethyldidodecylammonium bromide yields predominantly a syndiotactic polymer with high conversion and comparatively low polydispersity (M̄w/M̄w = 1.3−1.5). In some cases QAS additives are more effective modifiers than cryptand [2.2.2].
Hard domain compression of triblock‐copolymer gels by high pressure X‐ray small‐angle scattering
Authors: Lorenzen Maren , Bösecke Peter , Riekel Christian , Reynders Karen , Reynaers Harry , Overbergh Noel 
Published: April 2003

AbstractSmall‐angle X‐ray scattering using synchrotron radiation at pressures up to 700 MPa has been performed on triblock‐copolymer gels, polystyrene‐rubber‐polystyrene with poly(ethylene/butylene) as the rubber mid‐blocks. A 2‐stage pressure behaviour could be verified by comparison of the experimental data with the Tait‐equation and a model of pressure screening.
Ethylene polymerization with ansa‐metallocene systems rac‐(Me2SiOSiMe2)[Ind]2ZrCl2‐MAO and rac‐(Me2SiOSiMe2)[IndH4]MtCl2‐MAO; (Mt = Zr, Ti)
Authors: Liang Bo , Li Yong , Xie Guanghua 
Published: April 2003

AbstractEthylene was polymerized in toluene using methylalumoxane (MAO) activated rac‐(Me2SiOSiMe2)[Ind]2ZrCl2 (1) and rac‐(Me2SiOSiMe2)[IndH4]2MtCl2 (Mt = Zr (2); Mt = Ti (3)). All three catalyst systems polymerize ethylene with high activity. The molecular weight of polymer produced with zirconocene (1) was up to a weight‐average molecular weight M̄w = 1.1 × 106 at low polymerization temperature (<20°C) under atmospheric pressure. The titanocene catalyst 3 shows lower activity and produced lower molecular weight polyethylene than zirconocenes 1 and 2. Replacement of aromatic rings in 1 by cyclohexane rings, leading to 2, increases activity and reduces molecular weight. The catalyst systems show a dependency of the activity on temperature.
Double‐stimuli‐responsive degradable hydrogels: interpenetrating polymer networks consisting of gelatin and dextran with different phase separation
Authors: Yamamoto Nobuyuki , Kurisawa Motoichi , Yui Nobuhiko 
Published: April 2003

AbstractBiodegradable interpenetrating polymer network (IPN)‐structured hydrogels consisting of gelatin (Gtn) and dextran (Dex) were prepared by sequential crosslinking reactions of Gtn and methacryloylated Dex. Phase separation of these hydrogels is dominated by preparation conditions, i.e., above or below the sol‐gel transition temperature (Ttrans) of Gtn. Enzymatic degradation by either α‐chymotrypsin or dextranase is hindered for the IPN‐structured hydrogel prepared below Ttrans whereas this hydrogel is perfectly degradable in the presence of both enzymes. Such a specific feature of enzymatic degradation was not observed for the hydrogel prepared above Ttrans. These results suggest that double‐stimuli‐responsive degradation of IPN‐structured hydrogels is related to their phase separation.
Mechanism of the anionic copolymerization of anhydride‐cured epoxies – analyzed by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS)
Authors: Leukel Jörg , Burchard Walther , Krüger Ralph‐Peter , Much Helmut , Schulz Günter 
Published: April 2003

AbstractThe mechanism of the strictly alternating anionic copolymerization of phenyl glycidyl ether (PGE) and phthalic anhydride (PA) was initiated by various imidazoles. Because of the strictly alternating copolymerization polyesters with a repeating unit of PGE‐PA were obtained. The mechanism of the reaction was analyzed by means of matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). With this technique the molar masses of the oligomers, the molar mass of the repeating unit, the weight‐average molar mass M̄w and the number‐average molar mass M̄n, their ratio M̄w/M̄n and the residual molar mass could be calculated. The strictly alternating copolymerization was easy to prove because the molar masses of PGE and PA are slightly different. The question whether the initiator remains chemically bound during the whole reaction could be solved. To this end polyesters obtained by initiation with various imidazoles with different molar masses were synthesized. The calculated residual molar masses correspond exactly to the molar masses of the imidazoles.