bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution properties of poly(octadecyl methacrylate) in butyl acetate, 1. Dilute Solution
Authors: Ricker Mathias , Schmidt Manfred 
Published: April 2003

AbstractDilute solutions of poly(octadecyl methacrylate) (PODMA) obtained by radical‐initiated polymerization were inverstigated in the theta‐solvent butyl acetate (BuAc) by static (SLS) and dynamic light scattering (DLS) and viscometry at six different temperatures between 11°C (near the theta‐temperature Θ) and 30°C. The mass‐average molar masses ranged from M̄w = 6,2 · 105 g · mol−1 to 3,2 · 106 g · mol−1. It was found that PODMA in BuAc behaves in general as expected for linear flexible Gaussian coils in a theta‐solvent. The Kuhn length was determined to be 35 Å. At temperatures slightly above Θ = 10,5°C the exponents of the intrinsic viscosity, radius of gyration and hydrodynamic radius versus molar mass relationships lie significantly below 0,5, the expected value for flexible linear chains at theta‐conditions. Qualitatively, these findings are explained by a coil contraction due to the different chemical nature of the main chain and the side chains and therefore different polymer‐solvent interactions of different parts of the molecules.
Polymer diffusion in mixtures of polystyrene and polymethylstyrene studied by forced rayleigh scattering and photon correlation spectroscopy
Authors: Wesselmann Manfred , Sillescu Hans 
Published: April 2003

AbstractTracer diffusion coefficients D* of both components were measured in mixtures of polystyrene (PS) and polymethylstyrene (PMS), a random copolymer from 60 wt.‐% of m‐methylstyrene and 40 wt.‐% of p‐methylstyrene. The results are interpreted in terms of the free‐volume theory which yields master curves even for “asymmetric” mixtures of oligomer and polymer chains, if D* is drawn versus the distance from the glass transition temperature, T–Tg. Whereas D* was measured by the forced Rayleigh scattering technique, we also studied photon correlation spectroscopy in these mixtures and observed “slow modes” with decay constants that correspond to diffusion coefficients 2–3 decades smaller than the interdiffusion coefficient.
External alkoxysilane donors in Ziegler‐Natta catalysis. Effects on poly(propylene) microstructure
Authors: Härkönen Mika , Seppälä Jukka V. , Väänänen Taito 
Published: April 2003

AbstractCorrelations were sought between the structure of an external alkoxysilane donor and the microstructure of the polymer chain obtained by the polymerization of propene with a heterogeneous, high‐activity Ziegler‐Natta catalyst. Fourteen different alkoxysilanes of structure RnSi(OR′)4‐n, where n = 1–3, R = n‐alkyl or phenyl and R′ = C1–3‐alkyl, were used as external donors. The polymers were fractionated by boiling heptane extraction. The microstructures of the polymers were studied by means of 13C NMR spectroscopy. The structure of the donor had a marked effect on the catalyst activity and isotacticity of the polymer. However, all of the alkoxysilanes tested produced qualitatively similar differences in the microstructure of poly(propylene): the size of the isotactic mmmm pentad peak varied with the donor efficiency, but the sizes of the non‐isotactic pentad peaks were more or less constant relative to each other. In the boiling heptane soluble fraction, isotacticity and syndiotacticity increased and the viscosity‐average molecular weight M̄v decreased when a good external donor was used in the polymerization. Results indicate that all external alkoxysilane donors tested have the same qualitative effect on active centers, and only isotacticity, i.e., the number of mmmm sequences, can be controlled by an external alkoxysilane donor. The effectiveness and selectivity of deactivation strongly depend on the structure of the donor.
Kinetics of the anionic polymerization of ϵ‐caprolactone with K+ · (dibenzo‐18‐crown‐6 ether) counterion. Propagation via macroions and macroion pairs
Authors: Sosnowski Stanislaw , Slomkowski Stanislaw , Penczek Stanislaw 
Published: April 2003

AbstractFollowing our earlier work on the polymerization of lactones involving crowned cations, kinetics of the anionic polymerization of ϵ‐caprolactone (ϵCL) with K+ · (dibenzo‐18‐crown‐6 ether) (K+DB18C6) counterion was studied calorimetrically in THF solution in the temperature range from 0 to 20°C. Dissociation constants of CH3(CH2)5O−K+DB18C6, modelling the active centers, were determined conductometrically: KD (20°C) = 7,7 · 10−5 mol · dm−3, ΔH = 9,3 ± 0,2 kJ · mol−1, ΔS = −47 ± 2J · mol−1 · K−1. From kinetic measurements and from measurements of the dissociation constant of CH3(CH2)5O− K+DB18C6, rate constants of propagation via macroions and via macroion pairs were determined. Activation parameters for propagation via these species are equal to: ΔH = 39,2 ± 0,2 kJ · mol−1, ΔS = −63 ± 1 J · mol−1 · K−1, ΔH = 13,7 ± 0,1 kJ · mol−1, ΔS = −185 ± 2 J · mol−1 · K−1. At 20°C, k = 3,50 · 102 dm3 · mol−1 · s−1 and k = 5,2 dm3 · mol−1 · s−1. Due to the large difference of ΔH≠ for propagation via macroions and macroion pairs (vide supra), the isokinetic point (k = k) would appear at −65°C.
Polymers with pharmacological activity, 5. Hydrolytical behaviour of polymethacrylic hydrogels bearing “paracetamol” side groups
Authors: Levenfeld Belén , Román Julio San , Bunel Claude , Vairon Jean‐Pierre 
Published: April 2003

AbstractThe heterogeneous hydrolytical behaviour of hydrogels based on copolymers of 2‐hydroxyethyl methacrylate (HEMA) with 4‐(methacryloyloxy)acetanilide (MOA)b is analyzed by measuring the concentration of active metabolites released into the alkaline‐buffered solution used as the hydrolytical medium. Previously, we studied the swelling of hydrogel matrices of copolymers prepared with a MOA content between 1,0 and 5,0 wt.‐%, in order to know the diffusional character of the reagents and the released species. The results obtained demonstrate that the swelling phenomenon is much faster than the hydrolytical chemical reaction. Thus, the hydrolysis is studied on the basis of a kinetic scheme which considers the formation of different kinds of residues, i.e., the sodium salts of 4‐hydroxyacetanilide (PC) and 4‐aminophenol (PA), according to the UV spectra obtained at different times of treatment. The characteristic rate coefficients, k1, k2, kc and k′c are evaluated from the experimental data on the basis of the suggested kinetic scheme.
Grafting of acrylonitrile to poly(styrene‐co‐acrylonitrile) by transformation with a titanium catalyst
Authors: Menceloğlu Yusuf Z. , Güngör Attila , Baysal Bahattin M. 
Published: April 2003

AbstractPoly(styrene‐co‐acrylonitrile)‐graft‐polyacrylonitrile graft copolymers were prepared using a mixed (free‐radical Vanionic) mechanism technique. For this purpose, poly(styrene‐co‐acrylo‐nitrile) random copolymers which contain different amounts of acrylonitrile segments were regarded as saturated high‐molecular‐weight nitrile compounds and were allowed to react with tetrakis(dimethyl amino)titanium. By this treatment pendant nitrile groups were transformed to organometallic active sites. These active groups lead to the polymerization of acrylonitrile via an anionic insertion process. Polyacrylonitrile grafts were grown on the poly(styrene‐co‐acrylonitrile) backbone.
Surface properties of epoxy systems, 1. Influence of the chemical structure on surface energy of monomers, comonomers and additives
Authors: Chen Dong , Pascault Jean Pierre , Sage Daniel 
Published: April 2003

AbstractThe plate method was used to measure the surface tension of different epoxy prepolymers and different hardeners. The values are correlated to the chemical structure. The effect of molecular weight is very weak for diglycidyl ether of bisphenol A (DGEBA) prepolymers. For α,ω‐diamino‐terminated poly(propylene oxide) (PPO) oligomers, the surface tension remains constant when M̄n changes. However, the surface tension increases for PPO oligomers when the number of amino end‐groups increases, and for α,ω‐epoxy‐terminated oligomers when M̄n increases. These results are discussed in terms of a competition between the surface tension of the chain ends and the surface tension of the constitutional repeating units. The surface tension of carboxy‐(CTBN) and epoxy (ETBN)‐terminated butadiene‐acrylonitrile random copolymers is lower than the value of DGEBA prepolymers. In homogeneous blends these oligomers have a surfactant effect.
Surface properties of epoxy systems, 2. Evolution of epoxy‐amine system with reaction time
Authors: Chen Dong , Pascault Jean Pierre , Sage Daniel 
Published: April 2003

AbstractWith the plate method we determined dynamically the surface tension of different epoxy‐amine systems. After different critical observations about the validity of this type of measurement during the reaction time, we were able to correlate the evolution of the surface tension with epoxy conversion. For epoxy systems based on cycloaliphatic diamines, the diamine is the low energy component in the monomer blend. As the diamine reacts, its concentration in the bulk decreases, the surface is improverished in surfactant, and the surface tension of the reactive system increases. A constant value is obtained when all the diamine monomer has been consumed. The final surface tension of a fully cured epoxy system without additive can be higher than any of the surface tensions of the initial reactants. But for rubber‐modified epoxy systems, the rubber is the component with the lowest surface energy, the surface properties of the reactive system are independent of the reaction time and very close to the surface properties of the rubber.
Synthesis of polymers containing pseudohalide groups by cationic polymerization, 2. Copolymerization of 3,3‐bis(azidomethyl)oxetane with substituted oxetanes containing azide groups
Authors: Cheradame Hervé , Gojon Eric 
Published: April 2003

AbstractThe cationic copolymerization of 3,3‐bis(azidomethyl)oxetane (BAMO) was studied, initiated by a mixture of boron trifluoride diethyl etherate/diethylene glycol (2,2′‐oxydiethanol). The copolymerization of BAMO with 3‐azidomethyl‐3‐(2,5‐dioxaheptyl)oxetane (AMDHO) and 3‐azidomethyl‐3‐(2,5,8‐trioxadecyl)oxetane (AMTDO) was investigated in order to obtain at the same time a decrease of the crystallization tendency and of the glass transition temperature of poly(BAMO). The interest in this copolymerization is linked with the fact that, when BAMO was copolymerized with 15 wt.‐% of AMTDO, it was possible to obtain bifunctional oligomers with a glass transition temperature in the −50 to −60°C range, without significant loss in the nitrogen content.
Synthesis and properties of processable rigid polymers containing spiroacetal moieties
Authors: Lee Kwang‐Sup , Kim Hyun Min , Rhee John M. , Lee Soo‐Min 
Published: April 2003

AbstractA series of rigid rod‐like polyspiroacetals bearing flexible side chains was prepared by interfacial polycondensation of 4,4′‐(2,4,8,10‐tetraoxaspiro[5,5]undecane‐3,9‐diyl)diphenol with 2,5‐dialkoxy‐substituted terephthaloyl dichlorides. The majority of these polymers were soluble in polar solvents like tetrahydrofuran (THF), dimethylformamide (DMF), CHCl3, phenol/CCl4 (1 : 1 by vol.) mixtures, etc. The molecular weights ranged from 7 600 to 15 000 and the melting temperature from 182 to 228°C. Both of the above values decreased with increasing length of the side chains. The TG curves revealed 5% weight loss at 350–370°C under N2 gas atmosphere. Wide‐angle X‐ray diffractograms showed that all of the polymers have considerable crystallinity at room temperature.
Effect of phosphoric acid on the polycondensation of ε‐caprolactone with δ‐valerolactone and biodegradation of their copolyesters
Authors: Imasaka Kazumichi , Nagai Tsuneji , Yoshida Masaru , Fukuzaki Hironobu , Asano Masaharu , Kumakura Minoru 
Published: April 2003

AbstractCopolycondensation of ε‐caprolactone (CL) and δ‐valerolactone (VL) was performed in the presence and absence of phosphoric acid, in order to clarify the competition between the ring‐opening reaction of lactones and the polycondensation of linear compounds produced by this reaction. The gel permeation chromatography data showed that the monomer peaks remained in the system even after 7 h from start of the reaction when polymerized in the absence of phosphoric acid and, on the contrary, in the presence of phosphoric acid the peaks disappear perfectly within 1 h. The weight‐average molecular weights (M̄w) of poly(CL‐co‐VL), obtained by copolycondensation with and without phosphoric acid at 200°C for 1 h, were approximately 540 and 8900, suggesting that phosphoric acid markedly accelerates not only the rate of ring‐opening but also the rate of copolycondensation. On the other hand, the biodegradation of the copolyesters obtained is characterized by the action of a lipase‐type enzyme, showing a typical parabolic‐type degradation pattern.
Synthesis and rheological study of some maleic acid and fumaric acid stereoregular polyesters, 6. Influence of some parameters on the polycondensation reaction of potassium maleate and 1,4‐dihalogenobutanes
Authors: Sepulchre Marie‐Odile , Sepulchre Maurice , Spassky Nicolas , Djonlagić Jasna , Jaćović Mihailo S. 
Published: April 2003

AbstractThe influence of several parameters on the polycondensation reaction of potassium maleate and 1,4‐dihalogenobutanes has been studied in 1‐methyl‐2‐pyrrolidone at moderate temperature. The yield and molecular weight of the obtained polyesters as well as the extent of trans isomerization and the nature of chain end‐groups depend strongly on the mole ratio of reagents, the nature of halogen in the 1,4‐dihalogenobutanes and on the presence of small amounts of water in the reaction mixture. In particular, it has been observed that water increases the consumption rate constant of 1,4‐dibromobutane but at the same time acts as a terminating agent.
Factor analysis applied to X‐ray diffraction diagrams of polymer blends
Authors: Zhang Hongfang , Yin Jinhua 
Published: April 2003

AbstractThe feasibility of applying the method of factor analysis to X‐ray diffraction diagrams of binary blends of polypropylene and ethylene‐propylene‐diene terpolymer (PP/EPDM) was examined. The result of mathematical treatment was satisfactory. The number of scattering species and their concentrations in six kinds of PP/EPDM blends were determined. The separation of the spectral peaks of each species in the blends, contributing spectral intensities, was carried out.
Photo‐degradable polymer microcapsules
Authors: Kitano Hiromi , Oehmichen Thomas , Ise Norio 
Published: April 2003

AbstractMicrocapsules were prepared by a coupling reaction of disuccinimido 4,4′‐azobis(4‐cyanovalerate)Systematic name: 5,5′‐bis(imidooxy)‐2,2′‐dimethyl‐5,5′‐dioxo‐2,2′‐azodipentanenitrile.
with L‐lysine, and/or polyallylamine in a water/oil emulsion system. The microcapsules show a light‐responsive release of an inner content, succinylated bovine serum albumin, to the outer bulk phase. Effects of the composition of the coupling suspension on the photo‐durability of the microcapsules obtained were examined. The microcapsules would be useful as a device of photo‐responsive systems.
Effect of the internal/external donor pair in high‐yield catalysts for propylene polymerization, 1. Catalyst‐cocatalyst interactions
Authors: Noristi Luciano , Barbè Pier Camillo , Baruzzi Giovanni 
Published: April 2003

AbstractThe chemistry of the catalyst‐cocatalyst interaction was investigated in systems containing different internal/external donor pairs. Qualitatively similar results were obtained with the ethyl benzoate/methyl p‐toluate (EB/MPT) and dibutyl phthalate/triethoxy(phenyl)silane (DBP/EPS) systems, which thus were assumed to follow the same model. Quantitative differences were accounted for by assuming a different basic strength of the two donor pairs towards MgCl2 and AlEt3.
Complex structure formation in thin microlithographic coating systems
Authors: Köhler Johann Michael , Weh Lothar 
Published: April 2003

AbstractA characteristic sequence of structures is observed during the curing process of bilayer systems of thin films of novolak and poly(vinyl alcohol). Patterns arise spontaneously in such thin film systems heated above 140°C. At first, cell‐like structures are formed followed by wave and ripple patterns. The temporal order of the formed features is in opposition to the well‐known order of dissipative structures of coupled hydrodynamical instabilities. The rate of pattern formation strongly increases with temperature and thickness of the novolak sublayer. The character of the final pattern depends on this film thickness, too.
A new procedure for the determination of molar mass distribution from sedimentation equilibrium runs in an analytical ultracentrifuge (AUC), 1. Measurements with interference optics
Authors: Lechner M. Dieter , Mächtle Walter 
Published: April 2003

AbstractA new procedure for the determination of the number‐, weight‐ and z‐average molar masses M̄n, M̄w and M̄z and a model molar mass distribution W(M) has been developed from measurements of the sedimentation equilibrium. The method is based on the determination of the experimentally measured reduced concentration profile by extrapolation to zero concentration and direct calculation of the molar mass distribution W(M) by nonlinear regression of the integral equation according to the Simplex procedure. Results obtained in different solvents for the well characterized polystyrene NBS 706 with broad distribution are reasonable. Generally, it can be concluded that the suggested procedure is a suitable possibility for the determination of molar mass average values and the molar mass distribution of polymers if the latter is a log‐normal, Schulz‐Flory or Poisson distribution.
Surface modification of poly(methyl methacrylate) by graft copolymerization
Authors: Ichijima Hideji , Okada Toshiyuki , Uyama Yoshikimi , Ikada Yoshito 
Published: April 2003

AbstractGraft copolymerization was carried out onto a poly(methyl methacrylate) (PMMA) plate for surface modification. The following treatments were conducted to introduce peroxides into the PMMA surface prior to graft copolymerization: UV irradation, corona discharge, glow discharge, and ozone exposure. The static contact angle of the PMMA plate toward water decreased from 66° to 45 and 38° by the pre‐treatment with corona and glow discharge for 5 min, respectively, whereas the pre‐treatment with UV irradiation and ozone exposure caused no appreciable decrease in contact angle. When graft copolymerization of acrylamide (AAm) was carried out onto the pre‐treated PMMA plates by near‐UV light irradiation to decompose the peroxides in the presence of riboflavin, the contact angle further decreased to approximately 20° and the amount of AAm polymer grafted was 20–25 μg · cm−2 for the pre‐treatments with corona discharge, glow discharge and UV irradiation. However, graft copolymerization was practically not achieved onto the PMMA plate pre‐treated with ozone exposure. On the other hand, when graft copolymerization was performed at 50°C after degassing without UV irradiation, the amount of AAm polymer grafted was always less than 10 μg · cm‐2, independent of the pre‐treatment methods.
Porosity determination of poly(trimethylolpropane trimethacrylate) gels
Authors: Schmid Andrea , Kulin Lars‐Inge , Flodin Per 
Published: April 2003

AbstractTrimethylolpropane trimethacrylate (TRIM) was suspension‐polymerized with toluene as poreforming agent. The concentration of the monomer (TRIM) in the porogen was varied between 20 and 50 vol.‐% of the organic phase. The poly(TRIM) particles had narrow particle‐size distributions. The porosity of the dry gels was studied with scanning electron microscopy, nitrogen adsorption/desorption and mercury porosimetry. All gels had bimodal pore‐size distributions. The size distribution of large pores (r > 50 Å) of solvent free poly(TRIM) broadened when the amount of TRIM was decreased. The pore‐size distributions of the swollen poly(TRIM) gel particles were calculated from size‐exclusion chromatography (SEC) results. The separation range for poly(TRIM) particles of polystyrene standards varied with the monomer concentration. A relationship between the pore‐size distribution of dry poly(TRIM) gels and those of swollen gels is proposed. Whether or not the structure of poly(TRIM) gels could be described as fractals is discussed.
Behaviour of ring‐shaped polymers in dilute solution. Quantitative calculation and experimental verification for molecular dimensions and second virial coefficient
Authors: Huang Jiaxian , Li Chunrong , Chen Guohua , Zhu Duanhui , Shen Jun , Liu Dongzhou 
Published: April 2003

AbstractRelationships between the ratios of the mean‐square radii of gyration gs and the second virial coefficients gA2 of ring‐shaped and linear polymers with the degree of polymerization P of the polymer and its Peterlin exponent ε in dilute solution were derived theoretically and numerical values calculated. The second virial coefficients of ring‐shaped and of linear polystyrene at 25°C in toluene were determined using light scattering. By verifying the theoretical calculation based on the experimental determination of this polymer‐solvent system with light scattering and other methods reported in the literature, the agreement between theoretical calculation and experimental results is shown. The correlation equations for linear (l) and ring‐shaped (r) polystyrene in toluene at 25°C A2, 1 = 8,06 · 10−3 · M0,224 and A2,r = 6,68 · 10−3 · M0,218 were obtained using light scattering.
Photosensitivity in doped and sensitized cis‐polyphenylacetylene
Authors: Yang Mujie , Zhao Jian , Zhang Wende , Shen Zhiquan 
Published: April 2003

AbstractThe photosensitivity in cis‐polyphenylacetylene (cis‐PPA, polymerized with rare‐earth catalysts) can be significantly enhanced by doping the PPA with I2 or FeCl3 and sensitizing with 4‐isothiocyanatofluorescein (F‐II) or 2,4,7‐trinitro‐9‐fluorenone (TNF), which are powerful sensitizers. The electrophotographic photoreceptor (P/R) device with cis‐PPA + F‐II (on Al substrate) appeared preferable in photosensitivity enhancement and showed good photosensitivity: dark decay 1,8 V/s; maximum rate of discharge 321 V/s; residual surface potential 22 V; discharge 89, 1%; photosensitivity 2,96 s−1. This is a new “family” of photosensitive materials which can be used in a duplicator.
Enzyme‐analogue built polymers, 29. The preparation of defined chiral cavities for the racemic resolution of free sugars
Authors: Wulff Günter , Haarer Jutta 
Published: April 2003

AbstractNew types of macroporous polymers containing chiral cavities were prepared for the racemic resolution of free sugars. As template monomers 6‐O‐methyl‐ and 6‐O‐benzyl‐αD‐galactopyranose 1,2;3,4‐tetra‐O‐bis(4‐vinylphenylboronate) (3c and b) as well as 1‐O‐methyl‐ and 1‐O‐benzyl‐βD‐fructopyranose 2,3;4,5‐tetra‐O‐bis(4‐vinylphenylboronate) (4c and b) were copolymerized with a large amount of ethylene dimethacrylate. After splitting off the respective templates, these polymers were used for the racemic resolution of the racemates of D,L‐galactose and D,L‐fructose, and also the racemates, of 1‐O‐methyl‐ and 1‐O‐benzyl‐D,L‐fructose. The polymer prepared from 3b yielded the highest selectivity for the racemic resolution of D,L‐galactose. In the case of fructose the benzyl‐ether‐imprinted polymers yielded the highest selectivity, especially for 1‐O‐methyl‐D,L‐fructose separation. Polymers imprinted with D‐galactose derivatives showed inverse selectivity by preferably absorbing L‐fructose from the racemate. Polymerization at lower temperatures usually yielded more selective polymers.
Copolymerization of styrene and methyl α‐cyanocinnamate, 2. Head‐to‐head and head‐to‐tail penultimate copolymerization
Authors: Kelen Tibor , Borbély János , Bednarski Ralf , Braun Dietrich 
Published: April 2003

AbstractBased on NMR investigations and on composition data it was concluded that the copolymerization of styrene with methyl α‐cyanocinnamate obeys a penultimate mechanism (reactivity ratios r2 = r′2 = 0) with both head‐to‐tail and head‐to‐head couplings. A theoretical treatment of the mechanism supplied correlations which fit experimental sequence distribution data.