bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalytic hydrolysis of nitrophenyl esters by means of cyclodextrins in presence of poly(sodium styrenesulfonate)
Authors: Seo Toshihiro , Kajihara Taketoshi , Iijima Toshiro 
Published: April 2003

AbstractThe catalytic hydrolysis of various nitrophenyl esters by α,β‐ and γ‐cyclodextrins (CD) in the presence of poly(sodium styrenesulfonate) (3) was investigated. In each system, on addition of 3 the hydrolysis was accelerated. It is suggested that the acceleration is enhanced with increasing contribution of the hydrophobic interaction between polymer 3 and CD and/or the phenyl ester substrate. It was found that 3 increases the concentration of both CD and the substrate in the reaction sphere, maintaining its reactivity and the ability to include the substrate into DC. It is assumed that the hydrophobic moiety is more easily formed with increasing molecular weight of 3, and has a loose domain structure. The addition of ethanol or sodium chloride was found to affect the catalytic activity of β‐CD or the conformation of the polymer chain.
Effect of composition on the entanglement density in random copolymers
Authors: Lomellini Paolo , Rossi Anna Grazia 
Published: April 2003

AbstractThe plateau moduli of poly(styrene‐ran‐acrylonitrile) and poly[styrene‐ran‐(methyl methacrylate)] copolymers are investigated. Plots of the plateau moduli versus composition of the copolymers show a large negative deviation from linearity in both cases. Molecular weights between entanglements are determined from the plateau moduli. The experimental data are discussed in terms of models recently proposed for miscible blends. The physical picture emerges of a random copolymer as a “forced miscible blend”.
Low temperature modification of polymers by triazolinediones, 2. On the mechanism of the electrophilic aromatic substitution with 4‐substituted 1,2,4‐triazoline‐3,5‐diones
Authors: Kuhrau Martin , Stadler Reimund 
Published: April 2003

Abstract4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione (2, PTD), like other triazolinediones, reacts with electron‐rich aromatic compounds to give an electrophilic substitution. The reaction of PTD with poly(oxy‐2,6‐dimethyl‐1,4‐phenylene) (1, PPE) is studied by UV and IR spectroscopy. Based on the kinetic measurements, three stages of reaction can be distinguished: a slow induction period; a period with strongly increasing reaction rate associated with the formation of a strongly absorbing species, probably a charge‐transfer complex, and conversion of most of the PTD; and finally a period with a slow decay of the previously formed absorbing species. Experiments with urazole or trifluoroacetic acid added at the beginning of the reaction prove that the strong increase in the reaction rate is due to autocatalysis by the urazole groups formed during the course of the reaction. A mechanism is proposed to account for the experimental findings.
Investigation of sequences in a poly(butadiene‐co‐trimethylvinylsilane) by metathesis degradation
Authors: Hubmann Ewald , Hummel Klaus , Dösinger Marianne , Pongratz Thomas , Saf Robert 
Published: April 2003

AbstractPoly(butadiene‐co‐trimethylvinylsilane) with a mole fraction of 13% trimethylvinylsilane was prepared with butyllithium as initiator. It was degraded by cross‐metathesis with (E)‐4‐octene or (Z)‐2‐butene in the presence of the catalyst WCl6/Sn(CH3)4. The mixtures of the degradation products were investigated by means of gas chromatography (GC)/mass spectrometry (MS) coupling; mass spectra of degradation products with 4‐octene are depicted and discussed. Sequences of up to six trimethylvinylsilane units inserted between 1,4‐linked butadiene were identified after degradation with 2‐butene. Trimethylvinylsilane inserted between 1,4‐ and 1,2‐linked butadiene was also found. Cyclohexenyl and cyclopentenyl compounds were the preferred cyclic metathesis products.
Catalytic activity of novel agglomerates composed of Fe4S42+and (MovO)3+species cross‐linked with a bulky difunctional ligand, 2,4,6‐trimethyl‐1,3‐benzenedithiolate
Authors: Ueyama Norikazu , Sugawara Takashi , Okamura Taka‐aki , Nakamura Akira 
Published: April 2003

AbstractThe (MoVO)3+‐containing [Fe4S4]2+agglomerate {(Ph4P)2[Fe4S4(tmbdt)2(MoVO)0,76]}n(tmbdt = 2,4,6‐trimethylbenzene‐1,3‐dithiolato) was synthesized by reaction of {(Ph4P)2[Fe4S4(tmbdt)2]}nand MoVOCl3(thf)2. The (MoVO)3+cation is coordinated to the sulfur ligands binding the [Fe4S4]2+core. The (MoVO)3+‐containing [Fe4S4]2+agglomerate exhibits catalytic activity for the reduction of azobenzene and phenylacetylene to hydrazobenzene and phenylethylene, respectively, by Et4NBH4inN,N‐dimethylformamide/alcohol.
Modified poly(ethylene‐co‐propene‐co‐1,4‐hexadiene) (EPDM) bearing acetylacetonato groups and its chelate crosslinking with Fe(III)
Authors: Huang Ying , Eichinger Bruce E. 
Published: April 2003

AbstractAcetylacetonato group‐bearing poly(ethylene‐co‐propene‐co‐1,4‐hexadiene) (EPDM) was prepared and its chelate by crosslinking reaction with ferric salts. The hydroiodination of residual double bonds in the EPDM terpolymer under phase‐transfer conditions and the substitution of iodine atoms in the hydroiodinated EPDM by acetylacetonato groups were studied. The ligand exchange reactions of acetylacetone with ferric trifluoromethanesulfonate (Fe(TFS)3) or ferric chloride in THF were explored by UV/Vis spectroscopy to find optimum conditions for the formation of the chelate complex ferric acetylacetonate. The results indicate that these two ligand exchange reactions are equilibrium reactions, and the addition of an organic base such as triethylamine can make the reactions go to completion. The character of the anion in the ferric salts has a significant effect on the ligand exchange reactions, which may be attributed to the different dissociation tendency of FeX bonds. The ligand exchange reactions in the polymer systems were studied, and Fe(III)‐chelate complex crosslinked EPDM elastogels with gel fractions higher than 90% were prepared. The mechanism of the chelate complex formation in the polymer systems is similar to that in model compound systems.
Analysis of the linear methods of determining copolymerization reactivity ratios, 9. Penultimate systems with r2 = 0
Authors: Kelen Tibor , Tüdős Ferenc , Braun Dietrich , Czerwinski Wojciech K. 
Published: April 2003

AbstractThe copolymerization equation considering the penultimate unit effect, the so called penultimate model, takes a simplified shape in the case of r2 = 0 (monomer 2, M2, does not homopolymerize). For this case a method analogous to the conventional KT(Kelen‐Tüdős)‐transformation for estimation of r1 and r1′ is proposed. The new method was verified by literature data for the system styrene/fumarodinitrile, polymerized with benzoyl peroxide at 70°C, yielding r1 = 0,062 and r1′ = 0,812. Classification of copolymerization curves by means of the classical copolymerization model permits to distinguish between three curve‐types: r1 < 2 (alternation with respect to M2), r1 = 2 (linear diagram with slope 0,5) and r1 > 2 (non alternating system). The penultimate model permits to generate further curve‐types of “S”‐shape with r1 > 2 and r1′ > 2 or r1 > 2 and r1′ < 2 (r1 = r1′ for classically behaving systems and r1 ≠ r1′ for non‐classically behaving systems).
Relationships between transport and equilibrium properties in ternary systems of unbranched alcohol/3‐heptanone/poly(1‐vinyl‐2‐pyrrolidone)
Authors: Gavara Rafael , Campos Agustín , Figueruelo Juan E. 
Published: April 2003

AbstractIntrinsic viscosities, [η], second virial coefficients, A2, and interaction potentials, g12, for the ternary systems alcohol (1)/3‐heptanone (2)/poly(1‐vinyl‐2‐pyrrolidone) (3), with the unbranched alcohols methanol, ethanol and 1‐propanol, were determined at 25°C. Taking into account the dependence of the viscometric interaction parameter, B, with the molecular weight of the polymer, the unperturbed dimensions parameter, KΘ, of the polymer was unambiguously obtained. Relationships between ΔKΘ (defined as ΔKΘ = ΔK − KΘ) and excess Gibbs energies, GE, and between excess viscosity, Δ[η], and GE allow to obtain equations relating A2 to ΔKΘ or to Δ[η]. Therefore, A2 can be evaluated from experimental data of [η].
Comments on some recent papers concerned with terpolymerizations involving maleic anhydride
Authors: Bevington John C. , Ebdon John R. 
Published: April 2003

AbstractDifferences between results for the compositions of terpolymers of styrene (S), maleic anhydride (MAH), and either methyl methacrylate or methyl acrylate may be due to the difference between the diluents used during the copolymerizations. It is agreed that the compositions of the copolymers are very different from those calculated on the basis of the appropriate binary copolymerizations. It is not certain that complexes of S and MAH are involved in the growth reactions.
Soluble poly(para‐phenylene)s, 3. Variation of the length and the density of the solubilizing side chains
Authors: Rehahn Matthias , Schlüter Arnulf‐Dieter , Wegner Gerhard 
Published: April 2003

AbstractThe synthesis of a variety of alkyl‐chain‐substituted poly(para‐phenylene) (PPP) derivatives, including those with systematically decreased density of side chains, is described, using for their preparation the Pd‐catalyzed polymerization method recently developed in Mainz (Mainz route to PPP's). The degrees of polymerization achieved range between 30 and 50, allowing the synthesis of structurally well‐defined and soluble PPP's with more than hundred 1,4‐phenylene rings attached to each other.
New polymer syntheses, 47. Synthesis of aromatic polyethers from silylated diphenols and activated dichloro‐substituted aromatics
Authors: Kricheldorf Hans R. , Jahnke Petra 
Published: April 2003

AbstractBis(trimethylsilyl)bisphenol‐A was condensed with 4,4′‐dichlorodiphenyl sulfone under various reaction conditions. Satisfactory yields and molecular weights of the resulting poly(ethersulfone)s were only obtained when the condensation was conducted in amide solvents (e. g., N‐methyl‐2‐pyrrolidone) in the presence of equimolar amounts of K2CO3. The purity of the solvent plays an important role for the molecular weights. By light scattering, weight‐average molecular weights (Mw's) up to 130000 were found. Further polycondensations were conducted with 2,6‐dichlorobenzonitrile, 2,6‐dichloropyridine or 3,6‐dichloropyridazine. For polyethers derived from 2,6‐dichlorobenzonitrile Mw's up to 106000 were found and for copoly(pyridine‐ether‐sulfone)s Mw's up to 220 000. The corresponding difluoroaromatics gave similar results. In contrast to the polycondensation of free diphenols with dihaloaromatics under alkaline conditions, no water is formed when silylated diphenols are used.
Influence of ethyl benzoate on copolymerization of styrene and 1‐hexene with the titanium‐based systems (α)‐TiCl3(H) and TiCl3 · 1/3 AlCl3
Authors: Benaboura Ahmed , Deffieux Alain , Sigwalt Pierre 
Published: April 2003

AbstractThe influence of ethyl benzoate (E.B.) on the copolymerization of styrene with 1‐hexene, initiated by isospecific Ziegler‐Natta catalysts α‐TiCl3(H)‐AlEt3 and TiCl3 · 1/3 AlCl3‐AlEt3 (mole ratio Al/Ti = 3), was examined. Ethyl benzoate was found to reduce the activity of the catalysts. In addition it leads, depending on the Ti catalyst, to opposite effects on the apparent reactivity order of the two monomers. Incorporation of styrene into the copolymers is reduced when E. B. is added to TiCl3 · 1/3 AlCl3‐AlEt3. On the contrary, a much higher incorporation of styrene is observed with α‐TiCl3(H)‐AlEt3 in the presence of E. B. For this system the calculated reactivity ratio varies strongly with increasing proportion of E. B.: for a mole ratio AlEt3/E. B. = 3, rS = 0,94 and rH = 1,46 and for AlEt3/E. B. = 2, rS = 8 and rH = 0,1. Changes in the stereoregularity of copolymers suggest that E. B. leads to an inhibition of the less stereospecific sites for TiCl3 · 1/3 AlCl3‐AlEt3, whereas its addition suppresses the stereospecificity of the α‐TiCl3(H)‐AlEt3 catalyst. Contributions of conventional cationic and/or radical processes to the copolymerization reaction were examined and may be ruled out.
Synthesis and in vitro degradations of low‐molecular‐weight copolyesters composed of L‐lactic acid and aromatic hydroxy acids
Authors: Imasaka Kazumichi , Nagai Tsuneji , Yoshida Masaru , Fukuzaki Hironobu , Asano Masaharu , Kumakura Minoru 
Published: April 2003

AbstractL‐lactic acid (LA) was copolycondensed with various aromatic hydroxy acids such as p‐hydroxybenzoic acid (HBA), p‐hydroxyphenylacetic acid (HPAA), and p‐3‐(hydroxyphenyl)propionic acid (HPPA) in the absence of catalysts, in order to investigate the copolymerizability and in vitro degradation. The results of 1H NMR spectroscopy and gel permeation chromatography (GPC) showed that the reaction proceeds quantitatively, but the molecular weight of the copolyesters is relatively low. The in vitro degradation pattern of copoly(LA/HPPA) was changed into an S‐type from a parabolic‐type with increasing HPPA content in the copolyester, in contrast to only parabolic‐type for both copoly(LA/HBA) and copoly(LA/HPAA).
Radical polymerization and block copolymerization initiated with ceric salt/aldehyde redox system
Authors: Sun Yanhui , Chen Xiangning , Feng Xinde 
Published: April 2003

AbstractAldehyde compounds exhibit very high reactivities towards ceric salt in initiating polymerization of acrylamide. In the presence of aldehyde compounds, the rate of polymerization is 8 times as high as the rate initiated by ceric salt alone. In nitric acid solution, the rate of polymerization decreases, but the accelerating effect of aldehyde compound becomes more obvious. Polyether prepolymer with aldehyde and groups also shows high activity towards ceric salt, with a relative rate of polymerization up to ca. 15, which can initiate acrylamide polymerization to form a block copolymer. The polymerization of acrylonitrile and methyl methacrylate initiated with ceric salt/aldehyde were also investigated.
Novel organosilicon‐containing polymers for an oxygen permselective membrane
Authors: Nagasaki Yukio , Kurosawa Koichi , Suda Makoto , Takahashi Seiji , Tsuruta Teiji , Ishihara Kazuhiko , Nagase Yu 
Published: April 2003

AbstractSynthesis and gas permeation measurements of several types of polymers from methylstyrene derivatives containing mono‐and bis(trialkylsilyl) group(s) were carried out. Upon radical homo‐and co‐polymerization of silicon‐containing monomers high‐molecular‐weight polymers were obtained. Results from gas permeation measurements showed that these types of silicon‐containing polymers exhibit fairly high oxygen permselectivity (ratio of oxygen and nitrogen permeation coefficients P/P = 3,1 − 4,6), keeping the oxygen permeation coefficients (P) in the range of between 1,4 · 10−9 and 4,5·10−9 cm3 (STP) · cm · cm−2 · s−1 · cmHg−1. From time lag measurements, it was found that permeation coefficients are dependent on the solubility of gases in the membranes rather than on diffusivity. Actually, the oxygen solubility coefficients increase with increasing silicon content in the polymers. Permselectivity of oxygen against nitrogen is governed by polymer constitution rather than by silicon content.
Fourier transform infrared spectroscopy of the polymorphic forms of syndiotactic polystyrene
Authors: Guerra Gaetano , Musto Pellegrino , Karasz Frank E. , MacKnight William J. 
Published: April 2003

AbstractInfrared spectra of syndiotactic polystyrene exhibiting various crystalline forms and modifications, and in the amorphous state, are reported in this contribution. In addition to strong conformational effects, the spectra demonstrate striking effects of chain packing. Several infrared spectral differences also exist between the two crystalline forms which present a trans‐planer conformation of the chains. Spectral changes are also reported for solution‐crystallized samples, which depend on the solvent present in the clathrate compound formed with the polymers.
Simulation of coupled modification reactions of polymers, 6. Kinetic aspects of the incomplete two‐stage α‐substitution of 1,4‐polybutadiene coupled with partial double‐bond shift
Authors: Hummel Klaus , Martl Michael G. 
Published: April 2003

AbstractThe kinetics of α‐substitution of 1,4‐polybutadiene, coupled with partial double‐bond shift, is calculated using a system of differential equations. The results are compared with those obtained by computer simulation (Monte Carlo calculation). In the model, hydrogen abstraction at CH2 takes place with rate constant k1 and substituents R are introduced. Reactions at CHR follow with rate constant k2. The fractions of the groups CH2, CHR, CR2, CH and CR are determined as a function of the degree of substitution φ (number of substituents in a molecular/degree of polymerization). For low values of φ or k1/k2, the solution of rate equations (simplified by considering triads of groups) and simulation give almost identical results. Simulation alone shows that the substitution is incomplete in the fully reacted polymer and the final composition depends on k1/k2.
Gradient high performance liquid chromatography of polymers, 2. Characterization of block copolymers of decyl and methyl methacrylate synthesized via group transfer polymerization
Authors: Augenstein Michael , Müller Michael A. 
Published: April 2003

AbstractStatistical and block copolymers of decyl (DMA) and methyl methacrylate (MMA) were synthesized via group transfer polymerization (GTP) and characterized by size exclusion chromatography (SEC) and gradient HPLC. For HPLC a normal‐phase solvent gradient of isooctane and THF was used; the chromatograms were recorded by evaporative light scattering detection (ELSD). The block copolymers were shown to contain substantial amounts of precursor homopolymer by gradient elution, even in those cases where SEC furnished a perfectly monomodal molecular weight distribution (MWD). Comparison of the respective HPLC elution characteristics demonstrated that block copolymers are more strongly retained than statistical copolymers of identical composition. Whereas the latter are eluted according to chemical composition, the elution of the block copolymers seems to be controlled by the length of the poly(MMA) block.
Immobilization of a block copolymer of styrene and quaternized 4‐vinylpyridine on latex and its effect on the cobaltphthalocyanine‐catalyzed oxidation of 2‐mercaptoethanol
Authors: van Streun Karel H. , Tennebroek Ronald , Piet Pieter , German Anton L. 
Published: April 2003

AbstractTo overcome mass transport limitations that are usually encountered on immobilizing highly active catalysts, cationic latex particles were used as support for tetrasodium phthalocyaninato‐cobalt(II)tetrasulfonate (2). The cationic. latex was prepared by emulsion copolymerization of styrene and divinylbenzene in the presence of a block copolymer from styrene and 4‐vinyl‐N‐methylpyridinium PS‐qPVP serving as surfactant. The latex‐bound system was found to considerably increase the reaction rate of the oxidation of 2‐mercaptoethanol in the presence of 2 as compared with the conventional polymer‐free system. Michaelis‐Menten kinetics was observed for all three systems investigated, that is the block copolymer‐stabilized latex system, the homogeneous block copolymer system and the quaternized 4‐vinylpyridine homogeneous homopolymer (qPVP) system. Although the stability of the latex and qPVP‐containing systems after successive runs is rather poor, this immobilization method shows the great potential value of anchoring highly active systems retaining high catalytic activity. The turnover number is increased on immobilizing the block copolymer compared with the homogeneous block copolymer solution. The Michaelis constant is hardly affected by immobilization. Due to conformational changes of the polymer chain on immobilization, a comparison between the latex system and the homogeneous system containing either homopolymer or block copolymer remains difficult.
Ionic conductivity and morphology of polymer electrolytes based on a side‐chain liquid‐crystalline polysiloxane containing oligooxyethylene spacers and 6‐cyano‐2‐naphthyl benzyl ether mesogens
Authors: Hsieh Chang‐Jyh , Hsiue Ging‐Ho , Hsu Chain‐Shu 
Published: April 2003

AbstractSolid polymer electrolytes with different stoichiometries were prepared from solvent‐cast mixtures of alkali metal salts with the side‐chain liquid‐crystalline polysiloxane 2. Differential scanning calorimetry, optical polarizing microscopy, X‐ray diffraction, and conductivity measurements revealed that both morphology and conductivity of the obtained complexes are dependent on the salt content. For the complexes formed from 2 with LiSO3CF3, the formation of a homogeneous phase occurred approximately at the mole ratio LiSO3CF3 to oxyethylene unit of 1/2. The conductivity of the complex gradually increases with increasing mole ratio LiSO3CF3/OCH2CH2. The highest conductivity at ambient temperature achieved was 4,8 · 10−6 S · cm−1, which corresponds to the complex with a mole ratio LiSO3CF3/OCH2CH2 of 1/1. For all complexes obtained the temperature dependence of the conductivity displays an unusual behaviour in the temperature range belonging to the glassy and glass transition states of the polymer and an Arrhenius‐type behaviour in the temperature range belonging to the liquid‐crystalline state of the polymer. For the complexes formed from 2 with various alkali metal salts, the conductivity decreases in the order LiSO3CF3 > LiClO4 > NaClO4 > LiBr > KClO4. This indicates that LiSO3CF3 is more effectively ionized by the oxyethylene units than the other salts.
The polarity of chain packing in native cellulose. A meridional electron diffraction analysis onvaloniafibres
Authors: Macchi Edgardo M. 
Published: April 2003

AbstractThe classical problem of chain‐packing polarity in native cellulose fibres is approached by electron‐diffraction analysis in fibrils of the algaValonia ventricosa. Meridional reflections up to the 12th layer line were registered and compared with the intensities calculated for one‐dimensional parallel and antiparallel models of the structure, projected upon thec‐axis. The results are compatible with cellulose molecules packed in parallel fashion, and with a stagger of the central chain with respect to that at the origin of +2,80 or +2,39 Å. Some consequences of the parallel structure with regard to the biogenesis of cellulose are discussed.
The effects of variation of a core ring system in the mesogenic side chain of liquid‐crystal polysiloxanes
Authors: Gray George W. , Hill Jonathan S. , Lacey David 
Published: April 2003

AbstractFourteen novel side‐chain polysiloxanes 2 and their alkene precursors 1 containing methylene‐cyclohexane, cyclohexane, benzene, bicyclooctane, 3‐oxobicyclooctane, bicyclohexane and biphenyl moieties in the mesogenic core, and with (CH2)n spacer lengths of n = 3, 6 and 11 are reported. The order of efficiency of these cyclic moieties in promoting liquid‐crystal properties in the polymers is the same as that observed for the precursor alkenes, indicating that similar qualitative structural rules govern mesophase type and thermal stability in both monomeric and macromolecular systems. The apparent occurrence of smectic C properties for two of the polymers is particularly interesting.