bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cation binding properties of poly(crown ether)s with photodimerizable groups. Enhanced cation binding ability via a photochemical template effect
Authors: Shirai Masamitsu , Ueda Akihiko , Tanaka Makoto 
Published: April 2003

AbstractPolymers having both crown ether moieties as cation binding sites and cinnamic acid ester moieties as photodimerizable pendant groups were prepared. On irradiation with UV light the cinnamic acid ester groups of the polymers caused dimerization in dilute solution without formation of any insoluble material. Irradiation was carried out in THF and THF‐methanol (1 : 1 vol. ratio) in the absence and presence of cations as a template, respectively. The cation binding properties were investigated by means of the method of picrate salts extraction. The cation extractability of the photoreacted polymers was higher than that of the original polymers. Furthermore, the cation binding ability of the photoreacted polymers was less sensitive to temperature than that of the original polymers. The effect of the degree of photodimerization of the polymers, of the kind of cations used as a template during photodimerization of the polymers, and of the concentration of the template action on the extractability of polymers were investigated in detail.
Graph theory of configurational and viscoelastic properties of polymers
Authors: Yang Yuliang , Yu Tongyin 
Published: April 2003

AbstractA simple method for calculating the moments of the radius of gyration of polymers is developed. It can be applied to any molecule which does or does not possess close circuits in its structure. In the Rouse theory of viscoelastic behaviour, various functions such as the zero‐shear‐rate viscosity, η0, and the steady‐state recoverable compliance, J, are directly related to the moments of the radius of gyration and hence the results obtained may prove useful for interpreting rheological data.
Polybutadiène hydroxytéléchélique, 7. Cinétique de polycondensation en solution et en masse du polybutadiène hydroxytéléchélique avec le méthylène‐4,4′ di(isocyanate de phényle) en l'absence de catalyseur. Etude par 1H NMR et 13C NMR
Authors: Ghafari Mahmoud El , Pham Quang Tho 
Published: April 2003

AbstractQuantitative determinations by 13C NMR performed with insoluble polyurethanes allow to study the kinetics of the polymerization in bulk between hydroxytelechelic polybutadiene G 1000 and 4,4′‐methylene diphenylisocyanate (MDI). Comparisons have been made with (G 1000 + MDI) polymerization and (monoalcohol or G 1000 + phenyl isocyanate) model reactions in toluene. With [NCO]/[OH] = 1 and T ⩽ 60°C, in solution as well as in bulk, conversions are not complete. Because of the presence of gels, part of the reactive functions have been found to be trapped. For kinetic tests, only the first stage of the polymerization (conversion < 70%) may be taken into account. In bulk, the two alcohol functions are equally reactive, whereas in toluene, the hydroxylated 1,4 ends of the polybutadiene chains are more reactive. As evidenced for model reactions in the foregoing paper of this series, the kinetics fit better with the 3rd order than with the 2nd order equation. Nevertheless, at higher temperatures, the 2nd order may be used. The autocatalysis phenomenon found effective for model reactions is negligible in polymerization. All kinetic constants and activation parameters calculated must be considered to be apparent ones only.
Etude de nouvelles membranes asymétriques à base de copolymère à blocs styrène‐isoprène‐styrène, 1. Synthèse, modification chimique et caractérisation
Authors: Harjanto Fadjar , Mendjel Hocine , Sledz Joseph , Schué François , Meyer Guy 
Published: April 2003

AbstractA styrene‐isoprene‐styrene block copolymer was selected for the preparation of new asymmetric membranes which have blood compatibility properties after chemical modification by addition of gazeous N‐chlorosulfonyl isocyanate to the double bonds of the polyisoprene sequences. The membranes were examined with a scanning electron microscope. The permeability of the membrane was studied as a function of time, pressure and viscosity.
Dégradation du poly(carbonate de bisphénol‐A) en phase liquide en présence de sels alcalins. Etude cinétique
Authors: Godard Pierre , Bailly Christian , Legras Roger , Mercier Jean‐Pierre 
Published: April 2003

AbstractThe degradation of poly(oxycarbonyloxy‐1,4‐phenyleneisopropylidene‐1,4‐phenylene) [poly‐(bisphenol‐A carbonate)] in cyclohexanone is shown to be efficiently catalyzed by organic salts and metal carbonates. The catalysis is of homogeneous type. More precisely, only the associated fraction of the dissolved salt is active. The apparent activation energy of the degradation ranges between 113 and 130 kJ · mol−1 (27 and 31 kcal · mol−1), being similar to energies usually observed for hydrolysis or alcoholysis of esters. A reaction mechanism based on the ketoenolic equilibirum in cyclohexanone is proposed to explain the fast degradation observed. The influence of the nature of ions is also assessed: the reactivity increases with decreasing cation diameter, whereas the nature of the anion is of no matter.
Equilibrium polymerization with a multifunctional initiator
Authors: Yan De‐yue , Cai Gang‐feng 
Published: April 2003

AbstractThe equilibrium polymerization with a multifunctional initiator is re‐treated theoretically. The expressions for the molecular weight distribution function, the number‐ and weight‐average degrees of polymerization, the distribution of the degree of branching and the average degree of branching of the polymer formed are rigorously derived. All the formulae given are much simpler than those reported by Baur and Eisenberg. A theoretical method is established by which all the molecular parameters of the polymer can be calculated from polymerization conditions, such as the equilibrium constants, the functionality of the initiator and the initial concentrations of initiator and monomer.
Graph theory of viscoelasticities for polymers with starshaped, multiple‐ring and cyclic multiple‐ring molecules
Authors: Yang Yuliang , Yu Tongyin 
Published: April 2003

AbstractThe graph method of linear viscoelasticities of polymers has been extended to calculate the relaxation spectra and shrinking factors of star‐shaped molecules, multiple‐ring molecules and cyclic multiple‐ring molecules. The results obtained are general solutions, by which the special case can be easily calculated and compared with literature if available. This shows that graph theory is very versatile in theoretically treating linear viscoelasticities.
Addition reactions of polymers containing pendant cyclic iminoethers with thiols, carboxylic, thiocarboxylic and sulfinic acids
Authors: Nishikubo Tadatomi , Tokairin Atsushi , Torikai Shigeru , Iizawa Takashi 
Published: April 2003

AbstractPoly[1‐(2‐oxazoline‐2‐yl)ethylene] (2a), poly[1‐(5‐methyl‐2‐oxazoline‐2‐yl)ethylene] (2b), poly[1‐(4,4‐dimethyl‐2‐oxazoline‐2‐yl)ethylene] (2c), poly[1‐(4,4‐dimethyl‐5,6‐dihydro‐4H‐1,3‐oxazine‐2‐yl)ethylene] (2d), and poly[1‐(4,4,6‐trimethyl‐5,6‐dihydro‐4H‐1,3‐oxazine‐2‐yl)ethylene] (2e) were synthesized with high yields by radical polymerization, using AIBN as initiator. Polymer 2a was found to be soluble in water and in organic solvents such as methanol, acetone, chloroform and benzene, polymer 2b in hot water and in the same organic solvents, and polymers 2c and 2d are insoluble in cold and hot water. However, polymers 2d and 2e are soluble in diethyl ether and hexane. Addition reactions of polymers 2a–e with carboxylic acids and thiols were investigated. Reactions of polymer 2a with acetic acid, benzoic acid and cinnamic acid at 110°C for 10 h proceeded with 57–74 mol‐% conversion in DMF, NMP and DMSO, and reactions with benzenethiol and thiobenzoic acid quantitatively under the same reactions conditions. Reactions of polymers 2b and 2c with carboxylic acids proceeded with 4–36 mol‐% conversion, and with benzenethiol and thiobenzoic acid with 80–96 mol‐% conversion. From the results the following order of reactivities of these polymers may be suggested: 2a ≃ 2d > 2e > 2b > 2c. According to their higher nucleophilicity, the reactivities of benzenethiol and thiobenzoic acid towards the pendant 2‐oxazoline ring are much higher than those of carboxylic acids.
Synthesis of poly(vinyl alcohol)/poly(dimethylsiloxane) graft copolymer
Authors: Tezuka Yasuyuki , Fukushima Akira , Imai Kiyokazu 
Published: April 2003

AbstractPoly(vinyl acetate)/poly(dimethylsiloxane) graft copolymer (4a), with a controlled poly(dimethylsiloxane) graft chain length, was synthesized by radical copolymerization of vinyl acetate with poly(dimethylsiloxane) (3) having a dimethylvinylsilyl end group. 3 was prepared by living anionic polymerization of hexamethylcyclotrisiloxane (1) with butyllithium and subsequent termination with chlorodimethylvinylsilane (2). Poly(vinyl alcohol)/poly(dimethylsiloxane) graft copolymer (4b) was then synthesized by selective saponification of the poly(vinyl acetate) segments in the graft copolymer 4a with K2CO3 in methanol.
The chemical dehydrochlorination of poly(vinyl chloride), 1. Studies on tetrahydrofuran solutions
Authors: Bowley Heather J. , Gerrard Donald L. , Maddams William F. , Paton Mark R. 
Published: April 2003

AbstractThe chemical dehydrochlorination of poly(vinyl chloride) was studied in solution in tetrahydrofuran. Two materials, a mass polymer of 55% syndiotacticity and a low temperature polymer of 63% syndiotacticity, were dehydrochlorinated with potassium hydroxide and with potassium tert‐butoxide. The dehydrochlorination products were characterised by their chlorine contents and by UV/visible, IR and Raman spectroscopy, as a function of reaction time. The course of the reaction was found to be substantially independent of tacticity and the dehydrochlorinating reagent. Initially, the reaction follows a similar path to that occurring during photo‐ and thermal degradation, but as the dehydrochlorination continues, longer conjugated polyenes are formed than by these two latter processes. Sequences of 60 double bonds occur at the dehydrochlorination levels of about 55% that are attained after reaction times of 24 h. These sequences are sterically protected from cross‐linking reactions by the presence of longish sequences of unreacted CHClCH2 units.
Micelle‐forming block copolymers: Pinocytosis by macrophages and interaction with model membranes
Authors: Pratten Margaret K. , Lloyd John B. , Hörpel Gerhard , Ringsdorf Helmut 
Published: April 2003

AbstractA block copolymer (6) with both hydrophilic and hydrophobic regions was synthesized, in order to examine its interaction with model membranes and its uptake by living cells. The copolymer comprised poly(ethylene oxide) and poly(L‐lysine) with 50 mol‐% substitution of the ε‐amino groups with palmitoyl groups. To permit 125I‐labelling, p‐methoxyphenyl residues (1–4 mol‐%) were incorporated into the block copolymer and into a poly(ethylene oxide) used for comparison. Sudan Red 7 B solubilization studies indicated that the block copolymer, but not the homopolymer, forms micelles. Differential scanning calorimetry of dipalmitoyl‐phosphatidylcholine liposomes indicated that the block copolymer interacts with and probably penetrates lipid membranes. Both poly(ethylene oxide) and the block copolymer were captured by rat peritoneal macrophages in vitro, and inhibitor studies indicated that uptake of both polymers was by pinocytosis. Rates of uptake were indicative of adsorptive pinocytosis, and it is concluded that both poly(ethylene oxide) and the block copolymer present a largely hydrophilic aspect which interacts positively with the cell surface.
Continuous fractionation and solution properties of PVC, 3. Pressure dependence of the solubility in single solvents
Authors: Geerissen Heinz , Roos Jürgen , Wolf B. A. 
Published: April 2003

AbstractFrom the break‐down in the viscosity and from the increase of the intensity of the scattered light, associated with the entrance into the two‐phase region, the pressure dependence of the demixing temperature of solutions of PVC 37 000, PVC 75 000 and PVC 100 000 in phenetole and PVC 75 000 in o‐xylene was measured up to 1 000 bar. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) The application of pressure increases the demixing temperatures of PVC in both solvents by about 1 K/100 bar. For a qualitative forecast of the pressure effects, the solubility parameter theory in combination with the corresponding states principle, and an empirical correlation to the relative distance of the critical demixing temperature to the melting point of the pure solvent were used. The results of both concepts are in accord with the experimental findings.
Continuous fractionation and solution properties of PVC, 4. Pressure dependence of the solubility in a mixed solvent
Authors: Geerissen Heinz , Roos Jürgen , Wolf B. A. 
Published: April 2003

AbstractUsing a self‐constructed light scattering apparatus, the pressure dependence of the demixing temperature of solutions of PVC 20 000, PVC 37 000 and PVC 70 000 in THE/water was determined up to 1 000 bar for different compositions of the mixed solvent. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) In contrast to the thetasolvents o‐xylene and phenetole, the solubility decreases with increasing pressure for all molecular weights and compositions under investigation typically by about 1 K/100 bar. The evaluation of the experimental findings demonstrates that the volume fraction of the nonsolvent in the mixed solvent, φ, is the variable that governs phase separation: For the present region of p and T, a given polymer solution demixes at a characteristic constant value of φ, no matter how it is reached. This fact allows the prediction of pressure influences from known pVT data of the pure components and measurements at atmospheric pressure. A qualitative theoretical understanding of the observed influences of p and T can be reached on the basis of the solubility parameter theory.
Continuous fractionation and solution properties of PVC, 5. Pressure dependence of the viscosity — influence of solvent
Authors: Geerissen Heinz , Roos Jürgen , Wolf B. A. 
Published: April 2003

AbstractViscosity measurements were carried out as a function of pressure and temperature with solutions of 8 wt.‐% PVC (Mw ≈ 75 000) in ten thermodynamically good solvents by means of a Searle‐type viscometer. A rollingxyhball viscometer was used for the investigation of the pure solvents. In all cases the viscosity increases in a more or less exponential manner when the pressure is raised. The viscosity ratio f1000 = η1000 bar/η1bar can be varied by the choice of the solvent from ca. 2 (tetrahydrofuran) to 3,0 (cyclohexanone) at 40°C. For a constant temperature of 40°C, the volumes of activation for the viscous flow of the solutions, V≠, or f1000 exceed that of the pure solvent, by typically 25%. The dependence of f1000 or V≠ upon temperature is not very pronounced. However, the greater the f1000‐values, the more marked are the temperature effects. The theoretical analysis of the data, including earlier measurements with PS, indicates that three terms contribute to f1000: the basic value (f1000)s stemming from the pure solvent, the value (f1000)p which the polymer would contribute under athermal conditions, and finally a thermodynamic term, (f1000)pa, considering the pull‐along effect (i.e. the specific forces a given segment exerts on other segments under variable thermodynamic conditions).
Extent of reaction, monomer conversion, and polymer yield in polycondensations
Authors: Elias Hans‐Georg 
Published: April 2003

AbstractThe extent of reaction of functional groups (pA), the extent of conversion of monomer molecules (qM), the true relative polymer yield (yp), the constitutional repeating unit‐based apparent relative polymer yield (y), and the monomer‐based apparent relative polymer yield (y) are defined and their interrelationships given. The use of y instead of yp overestimates the true yield, except in the limit of high degrees of polymerization. Use of y, on the other hand, always underestimates the true yield, especially at infinite degrees of polymerization. The correct expression for the calculation of the mass fraction of i‐mers in reactants with a Schulz‐Flory “most probable” distribution is given and shown to become identical with the usual approximation in the limit of vanishingly small mass of the leaving molecule.
Influence de la température de cristallisation sur la morphologie du polypropylène isotactique
Authors: Idrissi Mohamed Oulad Bouyahya , Chabert Bernard , Guillet Jacques 
Published: April 2003

AbstractThe isothermal crystallization of isotactic polypropene samples cooled from the melt is studied. Particular emphasis is given to the morphology which develops depending on the melting and crystallizing conditions. Thus, the evolution of birefringence for samples crystallized between −20°C and +150°C is explained in terms of a quadritic arrangement of lamellae. The evolution of the relative amounts of radial and tangential lamellae is followed by differential thermal analysis, small angle light scattering and optical polarization microscopy.
Poly(p‐hydroxycinnamic acid)
Authors: Elias Hans‐Georg , Tsao Jung‐Hsien (Louis) , Palacios Joaquin A. 
Published: April 2003

AbstractPoly(p‐hydroxycinnamic acid) was synthesized by thionyl chloride activated polycondensation of p‐hydroxycinnamic acid at ambient temperatures and by polycondensation of its various monomeric esters at elevated temperatures. The thionyl chloride activated polycondensation proceeds as a 2‐stage process, yielding reduced viscosities of up to 102 mL/g. 360 MHz proton NMR spectra indicate an all‐trans structure and the absence of side reactions. The polymer with a melting temperature of 313°C can be pressed into films.
Polymerization by phase transfer catalysis, 2 Polythiocarbonates by polymerization of Bisphenol A with thiophosgene
Authors: Tagle Luis H. , Diaz Fernando R. , Vega Juan C. , Alquinta Pedro F. 
Published: April 2003

AbstractPoly(oxythiocarbonyloxy‐1,4‐phenyleneisopropylidene‐1,4‐phenylene) (1) was obtained from 4,4′‐isopropylidenediphenol (Bisphenol A) and thiophosgene under phase transfer conditions, using quaternary ammonium and phosphonium salts and crown ethers as catalysts. The polymer was identified by IR and 1H NMR spectroscopy, and the molecular weights were estimated from inherent viscosity measurements. The influence of catalysts, solvent and thiophosgene addition was studied in order to find the best conditions. It was found that tetrabutylammonium bromide, dichloromethane and the addition of thiophosgene at once gives the highest yields and inherent viscosities. Other catalysts and solvents were less efficient or unefficient for this reaction.
Über die quantenausbeute der kettenspaltung von polystyrol in lösung bei bestrahlung mit wellenlängen λ ≧ 270 nm
Authors: Wolinski Leszek , Witkowski Konrad 
Published: April 2003

AbstractValues of the mean number of chain scissions per macromolecule and the quantum efficiency of chain scission processes are presented for systems studied in our previous works, in which the photodegradation of polystyrene in solutions irradiated with mercury light (λ ≧ 270 nm) was investigated and changes of the weight‐average molecular weight M̄w were considered to be a measure for chain scission. The presented values of the number of scissions were obtained as follows: the molar mass distributions were determined for the investigated polystyrene samples by dynamic (quasielastic) light scattering experiments, before and after irradiation, the number‐average molecular weight values M̄n were calculated from these distributions and the mean number of scissions was obtained from the changes of the M̄n values.
A note on the intrinsic viscosity and huggins coefficient of low‐molecular‐weight polymers in mixed solvents
Authors: Caparros Ana Maria Rubio , Bohdanecký Miloslav 
Published: April 2003

AbstractIt is shown that in mixed solvents where preferential sorption takes place, the intrinsic viscosity and the Huggins coefficient contain contributions arising from the effect of preferential sorption on the viscosity of the mixed solvent surrounding the polymer molecules. These contributions become progressively more important as the polymer molecular weight decreases, and can be relevant at M ⪅ 104.
Chemical oxidation of a neutral electrochemically prepared polythiophene film
Authors: Cao Yong , Wang Ping , Qian Renyuan 
Published: April 2003

AbstractNeutral polythiophene films obtained by NH4OH compensation of electrochemically polymerized samples were re‐oxidized chemically to the metallic state by a wide range of oxidants. The electrochemically and chemically oxidized polythiophene films were found to be quite stable in air. Results of IR, SEM and WAXS studies are described and discussed. The feasibility of chemical re‐oxidation of neutral electrochemically prepared polythiophene films offers a convenient means to produce flexible highly conductive polythiophene films.
Copolymerization of 9‐anthrylmethyl methacrylate with N‐phenylmaleimide
Authors: Simionescu Cristofor I. , Grigoras Mircea , Onofrei Geta 
Published: April 2003

AbstractThe radical copolymerization of 9‐anthrylmethyl methacrylate (1) with N‐phenylmaleimide (2), initiated by 2,2′‐azoisobutyronitrile at 60°C in 1,4‐dioxane, was investigated. Simultaneously with the copolymerization a Diels‐Alder cycloaddition of 2 to the anthracene nucleus takes place as side reaction. A charge transfer complex formation between the two monomers was evidenced by 1H NMR spectroscopy. The stability constant of the complex, which is an intermediate in the cycloaddition reaction, was found to be 0,05 1 · mol−1.
Copolymerization of propylene with 1‐butene in presence of the catalytic system TiCl4/Mg[(CH2)5CH3]2
Authors: Soga Kazuo , Ohtake Makoto , Ohnishi Rikuo , Doi Yoshiharu 
Published: April 2003

AbstractThe copolymerization of propylene with 1‐butene was carried out in presence of the catalytic system TiCl4/Mg[(CH2)5CH3]2 in heptane. A transparent copolymer with a random distribution (r1 · r2 = 1,0) was obtained. The catalyst shows a considerably high activity. The rate of monomer addition was found to be independent of the chemical structure of the growing polymer chain end, which is quite different for the copolymerization of ethylene with propylene.
Polymerization of monomers containing functional groups protected by trialkylsilyl groups, 4. Studies on anionic living polymerization of 4‐(tert‐butyldimethylsilyloxy)styrene
Authors: Hirao Akira , Takenaka Katsuhiko , Packirisamy S. , Yamaguchi Kazuo , Nakahama Seiichi 
Published: April 2003

AbstractAnionic polymerization of 4‐(tert‐butyldimethylsilyloxy)styrene (2) was investigated under high vacuum conditions (≈ 10−6 mbar). 2 was readily polymerized by lithium naphthalide to form a “living polymer” at −78°C. By subsequent acid hydrolysis of the resulting polymer, a linear, nearly monodisperse polymer of 4‐vinylphenol of known molecular weight was obtained. Block copolymers of 2 with α‐methylstyrene were also prepared by means of this living system.
Organotin(IV) oxides and sulfides as modifiers of propene polymerization catalysts
Authors: Karayannis Nicholas M. , Lee Sam S. 
Published: April 2003

AbstractStudies of a number of organotin(IV) oxides and sulfides as modifiers of Ziegler‐type propene polymerization catalysts are reported. The general trend observed is that organotin(IV) sulfides provide better catalyst activity‐stereospecificity combinations than the corresponding oxides. Among the various modifiers studied, μ‐thiobis[tri‐butyltin(IV)] was found to exhibit the best overall modifying effect. Combination of an organotin(IV) sulfide with a second modifier of the aromatic amine, N‐oxide, phosphite ester or cyclic ether type in a binary modifier package was shown to lead to catalyst systems with excellent stereospecificities and activities ranging from acceptable to outstanding. Possible interactions and reactions of the organotin modifiers with the components of the catalyst system are discussed.