bluuebunny/crossref_metadata_2025_split huggingface dataset:
Terpolymérisation acrylonitrile‐styrène‐acrylate de méthyle, 5. Copolymérisation en emulsion styrène‐acrylate de méthyle en réacteur fermé en présence du styrène amorceur redox persulfate the potassium/hydrogénodisulfite de sodium
Authors: Ramirez‐Marquez Walter , Guillot Jean 
Published: April 2003

AbstractA series of emulsion copolymerizations of styrene (S) with methyl acrylate (MeA) initiated by the redox system potassium persulfate (KPS)/sodium hydrogen disulfite (SBS) was carried out at 50°C. The monomer feed composition and the monomer/water (M/W) ratios were widely varied. The polymerization rate was found to be higher than in the case when only KPS was applied. Initial (influence of polymerization in water phase) and final copolymer molecules (accumulation of MeA in the feed due to a lower reactivity) are richer in the more hydrophilic monomer (MeA). It could be shown that a high water solubility makes the emulsion reactivity ratios to be “apparent” kinetic parameters, which result in a higher number of azeotropic compositions, compared to bulk or solution, according to the M/W ratio. Particle sizes are smaller and the size distribution is larger than in polymerizations in the presence of KPS alone. Particle number (Np) tends to increase with conversion for monomer mixtures rich in MeA, contrary to S homopolymerizations in which Np remains constant. Comparison of Np and kinetic data suggests that only part of the particles in actually active in polymerization (N). N can be estimated assuming that the average number of radical per particle, ñ remains close to 0,5 – as found in a previous study – which gives also an estimate of very tiny particles generated at low conversion and undetectable by the usual QELS and MET techniques. The experimental data, to some extent, allow to quantify the competition between micellar and homogeneous nucleation mechanisms.
Liquid crystals from side‐chain mesogenic poly(vinyl ether‐alt‐maleic anhydride)
Authors: Frère Yves , Yang Fang , Gramain Philippe , Guillon Daniel , Skoulios Antoine 
Published: April 2003

AbstractAlternating copolymers of maleic anhydride with vinyl ethers, bearing a 4′‐methoxy‐4‐biphenylyl mesogenic group via an oligo(ethylene oxide) spacer, were synthesized and structurally characterized. From X‐ray diffraction observations, a smectic E phase was observed. Smectic layers are single layers of ribbon‐like polymer chains, with all pendant groups arranged in a single row and pending on the same side of the backbone. Mesogenic groups are oriented up and down at random, and polymer chains are aligned along the [110] direction of the rectangular lattice describing the packing of the pendant groups.
Group transfer polymerization of methyl methacrylate in acetonitrile, 1. Initiation by [(1‐methoxy‐2‐methyl)‐1‐propenyloxy]‐trimethylsilane
Authors: Sitz Hans‐Dieter , Speikamp Hans‐Dieter , Bandermann Friedhelm 
Published: April 2003

AbstractThe group transfer polymerization (GTP) of methyl methacrylate in acetonitrile with [(1‐methoxy‐2‐methyl)‐1‐propenyloxy]trimethylsilane as initiator and tetraethylammonium cyanide as catalyst is accompanied by a severe termination reaction of both the initiator and the active chains with the solvent leading to trimethylsilylacetonitrile and methyl isobutyrate or inactive polymer. Therefore, in order to work under reaction conditions characteristic for a living system acetonitrile as solvent has to be avoided.
Thermal and photoinitiated copolymerization of the cyclic disulfide lipoamide with styrene
Authors: Nambu Yoko , Acar Metin H. , Suzuki Tatsuki , Endo Takeshi 
Published: April 2003

AbstractThermal and photoinitiated copolymerizations of lipamide (1), a cyclic disulfide, with styrene in the absence of initiators were investigated. The thermal copolymerization is initiated via styrene radicals producing a copolymer with sulfide and disulfide linkages in the main chain and with amide and phenyl side groups. In the photopolymerization, the diradical formed by ringopening of 1 through homolytic fission of its strained disulfide bond is the main initiating species, attacking styrene to produce a copolymer with a high content of monomeric units of 1.
Enzymatisch katalysierte peptidknüpfung von alanin an phenylalaninhaltige methacrylpolymere mittels α‐chymotrypsin
Authors: Rehse Henning , Ritter Helmut 
Published: April 2003

AbstractThe α‐chymotrypsin catalyzed peptide‐bond formation was demonstrated by coupling the monomer N‐methacryloylaminoundecanoylphenylalanine (3 c) with alanine‐tert‐butylester in a water/chloroform system yielding N‐methacryloylaminoundecanoylphenylalanylalanyl‐tert‐butylester (7). The kinetics of the corresponding α‐chymotrypsin catalyzed coupling of alanine‐tert‐butylester with methacrylic polymers containing aminohexanoylphenylalanine and aminoundecanoylphenylalanine as spacergroups was correlated with the Huggins coefficient of the polymer by viscosity measurements.
Vertically‐oriented charge mosaic microdomains by means of epitaxial growth
Authors: Ishizu Koji , Hayashi Takeo , Fukutomi Takashi 
Published: April 2003

AbstractVinyl alcohol (VA)/4‐vinylpyridine (4VP) graft copolymers were prepared by the macromonomer method. After domain fixing of the PVA matrix of this graft copolymer, the water/1‐propanol mixed solution of poly(sodium p‐styrenesulfonate) (PSSS)/P4VP polymer blends was cast on the microheterophase surface of VA/4VP graft copolymer which served as a support membrane. The surface characterization of this composite membrane was carried out by means of transmission electron microscopy (TEM) and Electron Spectroscopy for Chemical Analysis (ESCA). The TEM observation indicated that charge mosaic microdomains formed by means of epitaxial growth are oriented perpendicularly to the film surface. The ESCA results clearly indicated that the two‐phase composition of the surface (in sampling depths of ≈ 1 and ≈ 5 nm) is proportional to the overall bulk composition of the polymer blends.
Oscillation of electrical current in water‐swollen polyelectrolyte gels
Authors: Osada Yoshihito , Umezawa Kayo , Yamauchi Aizo 
Published: April 2003

AbstractAn artificial oscillating system consisting of water‐swollen polyelectrolyte gels, to which a constant electric potential was applied, is described. It was found that repetitive oscillations occurred in three‐dimensional crosslinked gels made of synthetic polyelectrolytes, proteins and of polysaccharides. The repetitive oscillations were rather stable regardless of the “stimulating” current density, and the frequency was of the order 0,01 to 0,2 Hz which gradually decreased with time. Power spectra and Lorentz plots were obtained and a semi‐quantitative analysis of the oscillation was carried out.
Influence of chemical structure on glass transition temperatures of poly(propylene terephthalate) and poly(propylene isophthalate)
Authors: Pérez Crisantos , Guzmán Julio , Riande Evaristo , De la Campa José G. , de Abajo Javier 
Published: April 2003

AbstractPoly(propylene terephthalate)Systematic IUPAC name: poly(oxypropyleneoxyterephthaloyl).
(PPTP) and poly(propylene isophthalate)Systematic IUPAC name: poly(oxypropyleneoxyisophthaloyl).
(PPIP) were prepared by melt polycondensation. Different fractions with number‐average molar masses in the range 5 000 − 20 000 g·mol−1 were obtained and their respective glass transition temperatures (Tg) determined by calorimetry. The solubility parameters of the polymers were obtained by viscosity measurements in different solvents and were found to be 9,4 and 9,5 cal1/2·cm−3/2 (19,2·103 and 19,4·103 J1/2·m−3/2) for PPIP and PPTP, respectively. The glass transition temperatures were compared with those reported for analogous polyesters and it was shown that intramolecular interactions highly influence the Tg of these polyesters, whereas the effect of intermolecular interactions seems to be less important.
Contribution to the study of acrylamide polymerization, 1. Polymerization in the presence of an inhibitor
Authors: Vašková Viera , Oremusová Daniela , Bartoň Jaroslav 
Published: April 2003

AbstractThe average rate of initiation, Ri, is determined for the polymerization of acrylamide (AAM) in water in the presence of the water‐soluble initiator ammonium peroxodisulfate (APS) and the inhibitor 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (HTPO). The inhibitor and products from its interaction with the initiator to some extent participate also in other reactions: some lead to partial regeneration of inhibitor and some may be considered to be transfer reactions to the inhibitor. The determined ratio of the rate constant of termination and the square of the rate constant of propagation kt/k2p which does not significantly differ from the value listed for the AAM polymerization in water without admixtures, shows that participation of HTPO in propagation and termination reactions is not important.
Contribution to the study of acrylamide polymerization, 2. Polymerization in water/aliphatic alcohol mixtures
Authors: Vašková Viera , Oremusová Daniela , Bartoň Jaroslav 
Published: April 2003

AbstractThe polymerization of acrylamide is studied in mixtures of water and the aliphatic alcohols methanol, ethanol, 1‐propanol, and 2‐propanol in the presence and in the absence of the inhibitor 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (HTPO). The aliphatic alcohols reduce both the rate of polymerization and the molecular weight proportionally to their concentration in the mixtures with water and to the length and character of the aliphatic chain. Transfer constants to the individual aliphatic alcohols used are determined. The presence of the inhibitor HTPO leads to a further decrease of the molecular weight of the poly(acrylamide) formed.
Synthesis of soluble poly(divinylbenzene‐co‐styrene) and poly(divinylbenzene‐co‐vinylpyridine) by lithium amide‐initiated anionic copolymerization
Authors: Nagasaki Yukio , Taniuchi Masahiro , Tsuruta Teiji 
Published: April 2003

AbstractPolymerization of 1,4‐(or 1,3‐)divinylbenzene (DVB) in the presence of styrene initiated with lithium diisopropylamide was found to give soluble poly(DVB‐co‐styrene) having reactive vinyl group as pendant group of the polymer chain. The reactivity of 1,4‐DVB is higher than that of 1,3‐DVB in the copolymerization reaction with styrene as comonomer. It was found also that 1,4‐DVB can be copolymerized with 2‐vinylpyridine to form a soluble copolymer which consists primarily of 2‐vinylpyridine units.
Cationic transannular polymerization of 1,5‐cyclooctadiene
Authors: Yuan Cuiming , Yan Deyue , Xu Xiangming , Wang Fosong , Gong Zhi 
Published: April 2003

AbstractThe cationic transannular oligomerization of cis‐cis‐1,5‐cyclooctadiene (1), initiated by AlEtCl2 and Al2Et3Cl3, was studied. Several cationic catalysts were examined, and the order of activities of these catalysts was found to be the following one: BF3 · OEt2 < AlCl3 < AlEtCl2 < Al2Et3Cl3. The number‐average molecular weights of the resultant polymers are ≈ 1000 – 2000, and the softening temperature ranges 130 – 160°C. By means of NMR, IR and PC‐MS spectral analyses, the structure of poly(1,5‐cyclooctadiene), proposed earlier by Marvel et al., could be corroborated.
Synthesis and polymerization of a macromonomer derived from phosphatidylcholine
Authors: Ohkatsu Yasukazu , Yokota Masao , Kusano Toru 
Published: April 2003

AbstractA lecithin‐type macromonomer 1 was synthesized from natural egg phosphatidylcholine (lecithin). The macromonomer has an olefinic polymerizable group at the hydrophilic site, and is characterized by its chemical structure resembling lecithin. It could be polymerized in a liposome system by UV irradiation, giving polymers with a maximum molecular weight of 98 000. Polymers with molecular weights above 48 000 form thin and flexible membranes with a few 10 μm in thickness. The polymers can also be redispersed in water and the liposomes can be reconstituted.
Poly(vinylsaccharide)s, 4. Synthesis and polymerization of 6‐o‐methylallylgalactose derivatives
Authors: Klein Joachim , Blumenberg Klaus 
Published: April 2003

AbstractMethylallyl ethers of 1,2:3,4‐di‐O‐isopropylidene‐D‐galactopyranose and 1,2:3,4‐di‐O‐cyclohexylidene‐D‐galactopyranose were synthesized as new monomers containing saccharide moieties and copolymerized with maleic anhydride. The hitherto unknown 6‐O‐(2‐alkoxycarbonylallyl)‐1,2:3,4‐di‐O‐isopropylidene‐D‐galactopyranoses (8a and 8b; alkyl: methyl and ethyl, respectively) were prepared and polymerized under free radical conditions. The substances were characterized by 13C NMR, elemental analyses and molecular weight determinations. Water solubility of these polymers was obtained by removing the isopropylidene protecting groups. The inherent viscosities of these polymers, measured in 0,1 M Na2SO4 aqueous solution, were of the same order of magnitude as those of polyacrylamides of the corresponding degrees of polymerization.
Ring‐chain competition in kinetically‐controlled condensation polymerization
Authors: Yuan Xue‐Feng , Masters Andrew J. , Nicholas Christian V. , Booth Colin 
Published: April 2003

AbstractGordon and Temple's scheme of rate equations for ring‐chain competition reactions in condensation polymerization has been solved analytically (for very small rates of ring formation) and numerically over a wide range of conditions. The numerical method was computationally efficient. Except in extreme cases, the distribution of ring sizes was found to be practically the same as that predicted for equilibrium conditions by Jacobson and Stockmayer, viz. that the number concentration of rings with a degree of polymerization i is proportional to i−5/2 at the end of the reaction.
Radikalische hochdruckpolymerisation von ethylen im zweiphasensystem
Authors: Luft Gerhard , Fischer Norbert 
Published: April 2003

AbstractIn order to modify the properties of low density polyethylene (LDPE), the radically initiated polymerization of ethylene can be performed at pressures below 1200 bar and moderately high temperatures. Under such conditions the reaction mixture separates into a less dense phase, rich in monomer, and a dense phase, rich in polymer. The polymerization proceeds mainly in the monomer‐rich phase. When the polymer concentration exceeds the solubility limit, polymer precipitates from the monomer‐rich phase and moves into the polymer‐rich phase. By polymerization under two‐phase conditions, polyethylene resins with a narrow molecular weight distribution can be obtained.
Properties of poly(dimethylsiloxane) chains and gels in toluene and in toluene/ methanol mixtures
Authors: Aven Michael R. , Cohen Claude 
Published: April 2003

AbstractFour different samples of α‐dimethylvinylsilyl‐ω‐vinylpoly(oxydimethylsilanediyl) (α,ω‐divinylPDMS) chains of different molar masses have been endlinked in the absence of solvent to form “model” polymer networks. These networks have been subjected to swelling experiments at 30°C in toluene and toluene/methanol mixtures. The volume fraction of polymer in the gel at equilibrium swelling v3 is determined gravimetrically. The preferential sorption coefficient λ is found using interferometry. Large preferential sorption effects prevent the solvent mixtures from being treated as pseudo‐one‐component solvents. The variation of swelling and preferential sorption with network and solvent composition is discussed. The thermodynamic properties of α,ω‐divinylPDMS chains in dilute solution with toluene, toluene/methanol mixtures, and tetrahydrofuran are determined at 30°C using intrinsic viscosity measurements. Polymer‐solvent interaction parameters and Mark‐Houwink constants as well as unperturbed dimensions are determined in both the pure solvents and solvent mixtures.
Electro‐optical properties and molecular flexibility of polyelectrolytes in dilute solutions
Authors: Oppermann Wilhelm 
Published: April 2003

AbstractMeasurements of the electric birefringence of aqueous polyelectrolyte solutions in the very dilute regime ( ≈ 10−5 g · mL−1) reveal that the macroions are fully extended. However, this rod‐like conformation is easily altered towards a more coiled conformation when a strong static electric field is applied, particularly in the case of very high molar‐mass polymers. With the application of rectangular dc pulses, as ordinarily used in Kerr‐effect measurements, the change of molecular shape interferes with the transient rise and decay of the birefringence signal, because the rotational mobility as well as the optical anisotropy of the macroions become time‐dependent. As a result, the mean relaxation time for the rise curve is considerably smaller than that of the field‐free decay, and the steady‐state birefringence is much lower than expected for the unperturbed macroions. The change of the molecular shape can be avoided if the orientation of the macroions is induced by high‐frequency ac pulses. This experimental technique is therefore suitable to obtain the unperturbed shape and size of the macroions. A molecular interpretation for the dependence of the birefringence function on the pattern of the electric field is proposed.
Magnetic species present in styrene/methacrylic acid copolymers neutralized with cu(II)
Authors: Yamauchi Jun , Yano Shinichi 
Published: April 2003

AbstractElectron spin resonance (ESR) spectra of styrene/methacrylic acid copolymers neutralized with Cu(II) were observed at room temperature. Three magnetic species were detected; isolated Cu2+, Cu2+‐Cu2+ pairs of Cu(II) acetate monohydrate type and anhydrous Cu(II) formate type. One of the absorption patterns due to the Cu2+‐Cu2+ pair is the same as that of Cu(II) acetate monohydrate except linewidth. ESR data from the other species are summarized. ESR parameter, effect of the acid and Cu(II) contents, and spectral changes depending on sample preparation procedures or temperatures are discussed.
Influence of the far order effect on the reactivity of functional end groups of macromolecules in non‐equilibrium polycondensation
Authors: Ignatov Vladimir N. , Vasnev Valerii A. , Vinogradova Svetlana V. , Korshak Vasilii V. , Tseitlin Henrich M. 
Published: April 2003

AbstractThe influence of the number of oxyethylene repeating units in the oligomeric derivatives of ethylene bis(4‐chlorocarbonylbenzoate) (1, n = 3, 6,4, 13, 22,3, 45 and 68) on the reactivity of the chlorocarbonyl end groups in the acceptor‐catalytic esterification was determined by means of thermodynamic and kinetic investigations in diluted solutions. The violation of the principle of equal reactivity was found to be caused by the far‐order effect, when with increasing chain length the effective local concentration of oxyethylene repeating units increases in the environment of the end group whose reactivity is determined by the ratio between the “solvating ability” of the repeating units and the solvent. The far‐order effect influences not only the kinetics, but also the reaction mechanism.
Chain branching of poly(dimethylsiloxane): A competitive side reaction of the hydrosilylation reaction
Authors: He Xiongwei , Lapp Alain , Herz Jean 
Published: April 2003

AbstractPoly(dimethylsiloxane) (PDMS) fitted at both chain ends with dimethylsilyl functions was heated at 90 and 110°C in the presence of chloroplatinic acid. A chain‐branching reaction was observed yielding very‐high‐molecular‐weight species. The phenomenon, which occurs as well in solution as in the bulk, is temperature dependent. This reaction can exist as a side reaction of the hydrosilylation reaction between PDMS (1) and 1,4‐bis(dimethylvinylsilyl)benzene (2) or tetraallyloxyethane (5) when dimethylsilyl functions are in excess. However, it does not take place in hydrosilylations in which mole ratios 1/2 equal to unity or higher are applied.
Nuclear magnetic resonance studies on bacterial copolyesters of 3‐hydroxybutyric acid and 3‐hydroxyvaleric acid
Authors: Doi Yoshiharu , Kunioka Masao , Tamaki Akira , Nakamura Yoshiyuki , Soga Kazuo 
Published: April 2003

AbstractCopolyesters of 3‐hydroxybutyric acid (HB) and 3‐hydroxyvaleric acid (HV), P(HB‐co‐HV), were isolated from Alcaligenes eutrophus and characterized by solution NMR, solid‐state 13C CP/MAS NMR, and differential scanning calorimetry. The 13C CP/MAS NMR analysis was compatible with that of a random copolyester of oxy‐(1‐methyl‐3‐oxotrimethylene) (B) and oxy‐(1‐ethyl‐3‐oxotrimethylene) (V) units which adopts a regular conformation of a 21 ‐helix in the solid state throughout a wide range of compositions varying from 0 to 90 mol‐% V units. The chain dynamics of P(HB‐co‐HV) in chloroform was studied by analysis of the 13C and 1H NMR spectra. The carbon‐13 spin‐lattice relaxation times (T1) and nuclear Overhauser enhancements (NOE) indicated that the copolyester molecules in chloroform are not rigid but rather flexible. The conformational preferences of the copolyester molecules were determined by analysis of the 1H NMR spectra.
Polymers of 1‐azabicyclo[4.2.0]octane, 1. Structure of monomer and homopolymer
Authors: Mühlbach Klaus , Schulz Rolf C. 
Published: April 2003

AbstractThe structure of 1‐azabicyclo[4.2.0]octane (1) was evaluated by NMR spectroscopy. It was found that the six‐membered ring has a chair conformation with the four membered ring in the N‐axial and C‐6‐equatorial position, and as a consequence, the monomer allows neither a ring inversion nor a nitrogen inversion. It possesses two centers of chirality, one at the nitrogen atom and one at C‐6. Homopolymerization was carried out in methanol at 60°C with N‐alkyl ammonium salts of 1 affording the polymer in high yield within a few hours. Its NMR spectra reveal that the polymer chain is preferably arranged in the biequatorial position of the six‐membered ring. As a polybase the polymer can be titrated quantitatively with acids. Its glass transition temperature is 8°C, the decomposition starts at 320°C.
Synthesis and rheological study of some maleic and fumaric acid stereoregular polyesters, 2. Polyesters derived from 1,4‐dibromobutane or 1,8‐dibromooctane
Authors: Jaćović Mihailo S. , Djonlagić Jasna , Sepulchre Maurice , Sepulchre Marie‐Odile , Leborgne Alain , Spassky Nicolas 
Published: April 2003

AbstractConfigurationally pure, high‐molecular‐weight poly(butylene maleate)s, poly(butylene fumarate)s, poly(octamethylene maleate)s, and poly(octamethylene fumarate)s were synthesized by reaction of the corresponding potassium dicarboxylates and dibromoalkanes in 1‐methyl‐2‐pyrrolidone at 95 to 114°C. The polyfumarates show about ten times higher dynamic viscosities at 150°C than the polymaleates of the same limiting viscosity numbers, which might be attributed to the more extended conformations of the former.