bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallization kinetics of 1,4‐trans‐polyisoprene, 2. Polymer‐diluent mixtures
Authors: Chaturvedi Prakash N. 
Published: April 2003

AbstractFour mixtures of 1,4‐trans‐polyisoprene with methyl oleate (vol. fraction of polymer: 0,696 to 0,092) were prepared, and a dilatometric study of the crystallization kinetics was carried out in a convenient temperature range. The polymer was found to crystallize in the form of its high melting polymorph. The amount of secondary crystallization was less compared to that observed earlier for undiluted polymer. Formation of crystalline phase was found to be more difficult. In the absence of nucleation and growth data, the actual differences in interfacial energies required for nucleation and growth could not be estimated quantitatively, however, the experimental results indicate that compared to the bulk system, the energy requirements for the primary nucleation act in case of mixtures are higher. The interfacial energy σ′e (calculated after neglecting the transport term) was in the range 2309–2356 cal/mol for all the mixtures and showed appreciable variation with change in polymer concentration. A molecular interpretation of the possible mechanism operating in the crystallization of mixtures is given.
Enantioselective polymerization of (R,S)‐α‐methylbenzyl methacrylate initiated with products resulting from grignard reagents and axially dissymmetric [1,1′‐binaphthyl]‐2,2′‐diamine
Authors: Kanoh Shigeyoshi , Kawaguchi Naotaka , Suda Hiroshi 
Published: April 2003

AbstractEnantioselective polymerization of (R,S)‐α‐methylbenzyl methacrylate [(R,S)‐3] was investigated in tolurene at −30°C with a variety of chiral anionic catalysts, prepared in situ by reaction of axially dissymmetric [1,1′‐binaphthyl]‐2,2′‐diamine (1) and Grignard reagents (RMgX, R = alkyl). The enantioselectivity was found to be dependent upon the halogen ions of RMgX, but scarcely upon the alkyl groups. The catalyst systems involving (R)‐1 polymerize more or less preferentially (S)‐3 over (R)‐3. The selectivity is also discussed with respect to the mole ratio of RMgX to 1. The system cyclohexylmagnesium bromide (cHexMgBr)/(R)‐1, in a mole ratio of 1,5:1,0, shows high selectivity, and the optical purity of the initially formed polymer was found to reach 83%. The change in the optical purities of polymer and unreacted monomer can be represented satisfactorily by the integrated composition equation for an “ideal” copolymerization of (R)‐and (S)‐monomers, and the enantioselectivity ratio, r, was estimated to be 10,6. The polymers produced are almost completely isotactic, and contain a binaphthyl moiety as initiator fragment.
Characterization of cellulose ethers by 13C NMR, 2. Structural determination
Authors: Zadorecki Pawel , Hjertberg Thomas , Arwidsson Margareta 
Published: April 2003

AbstractThe substitution pattern of ethyl O‐hydroxyethyl cellulose (EHEC) was studied using 13C NMR spectroscopy on the hydrolysates. The hydrolysates of hydroxyethyl cellulose (HEC) and ethyl cellulose (EC) were investigated as well. The high mobility in the hydrolysates gives a much better resolution than that of the corresponding polymer solutions. Beside the determination of the total degree of substitution, the specific substitution at O2 and O3 can be determined. In highly substituted samples it is also possible to directly determine the fraction of unsubstituted O6‐positions. However, the latter can be obtained for all samples by combining the NMR results of O2 and O3 substitution with the HPLC analysis of unsubstituted glucose, units. The effect of the substitution pattern on the resistance against enzymatic degradation was also investigated. The reducing‐end residues formed by enzymatic attack on EHEC are shown to be unsubstituted at O2. A qualitative comparison between the number of degradable positions according to earlier published results on HEC and changes in molecular weight shows a good correlation.
Polymerizable amphiphiles, 2. Micellization of 1‐O‐3‐(4‐vinylphenyl)propyl‐β‐D‐glucopyranose
Authors: Elias Hans‐Georg , Chung Daniel C. , Donkai Nobuo , Hellmann Goetz P. , Solc Karel , Nagai Katsutoshi 
Published: April 2003

Abstract1‐O‐3‐(4‐Vinylphenyl)propyl‐β‐D‐glucopyranose (1) undergoes in water a closed association under formation of N‐mers. The unimer/N‐mer association is directly visible in the Schlieren pattern of ultracentrifugal synthetic boundary experiments. Association numbers and mass‐concentration‐based equilibrium constants of association were calculated from the variation of N‐mer concentrations with unimer concentrations and from the concentration dependence of inverse apparent average molar masses as measured by both vapor phase osmometry and sedimentation equilibrium. Association numbers were also calculated from the combination of sedimentation coefficients with diffusion coefficients, sedimentation coefficients with intrinsic viscosities, and diffusion coefficients with interinsic viscosities as well as from the dependence of apparent mass‐average molar masses on inverse apparent number‐average molar masses. All methods gave in general different association numbers and equilibrium constants. The effect, which was not found for other non‐ionic amphiphiles, is probably due to the existence of consecutive equilibria between the unimer and a low molar mass P‐mer which associates to a higher molar mass R‐mer. Viscosity data are in agreement with the picture of a spherical micelle for the dominant P‐mers with about 10 water molecules per glucose residue. The micellization of 1 is both enthalpy‐ and entropy‐driven, in contrast to the micellization of 1‐O‐octyl‐β‐D‐glucopyranose which is a strictly entropy‐driven process.
Studies on the nature of order in a rigid random copolymer
Authors: Bechtoldt Harald , Wendorff Joachim H. , Zimmermann Hans J. 
Published: April 2003

AbstractThe transition from the nematic melt to the solid state in a rigid rod‐like copolymer was found to be characterized by unusual thermodynamic and kinetic properties. The transition occurred with negligible volume changes. The enthalpy and the entropy of the transition were found to be lower by at least one order of magnitude in comparison to the values usually observed for a crystal to nematic transition. The ordered solid state displays a glass transition and its structure is characterized by high symmetry, i.e., an orthorhombic one. Dielectric relaxation studies, investigations on the plastic flow properties of the solid state and studies on the dynamical mechanical properties revealed a high degree of rotational freedom already at room temperature in the solid state. These experimental findings led us to the conclusion that the solid state displays a three‐dimensional positional long range order but is rotationally disordered with respect to rotations about the long axes of the rod‐like molecules. The structure is similar to those of plastic crystals known for spherical molecules such as cyclopentane, or to smectic E modifications known for rod‐like molecules. Also the properties reported above for the rod‐like copolymers resemble those reported in the literature for plastic crystals.
Initiation of the polymerization of 1,3‐dioxolane with 2,4,5‐trisubstituted 1,3‐dioxolan‐2‐ylium salts, 2. Reaction of the initiator with the polymer. Model studies
Authors: Gibas Mirosław 
Published: April 2003

Abstract2‐Mono‐ and 2,4,5‐trisubstituted 1,3‐dioxolan‐2‐ylium salts were reacted with dimethoxymethane representing the model of the polydioxolane chain. The products were identified and analysed by means of 1H NMR spectroscopy and gas chromatography. The reaction was found to proceed mainly via interchange of the C‐2 carbon atom of the salt and the methylene group of dimethoxymethane yielding 1,3‐dioxolane or 4,5‐disubstituted dioxolane and the unstable dimethoxymethylium derivative, which decomposes into the respective methyl ester and methyl cation. The formation of some by‐products follows the main reaction path. The amount and the kind of substituents as well as the configuration influence the reactivity of the salts in the processes investigated.
Syntheses of unsaturated polyesters containing betulinol moieties
Authors: Vasnev Valerii V. , Konkina Irina N. , Korshak Vasilii V. , Vinogradova Svetlana V. , Lindberg Johan J. , Jääskeläinen Pirja , Piiroinen Kaija 
Published: April 2003

AbstractSyntheses of polymers on the basis of betulinol (1), a pentacyclic triterpene glycol obtained from the birch bark, were investigated. Catalytic polyesterification of 1 with terephthaloyl chloride in various solvents gave only oligomers. Kinetic investigations indicated a very low activity of the hydroxyl groups of 1. Chemical modification of betulinol revealed the possibility of a successful addition of its OH‐groups to anhydrides at high‐temperature. Unsaturated polyesters, based on maleic anhydride, betulinol and acyclic glycols, were synthesized and investigated. Samples of betulinol‐containing polyesters cured by copolymerization with styrene show improved water and chemical resistance.
Emulsion polymerization of butyl methacrylate initiated by 2,2′‐azoisobutyronitrile, 1. Kinetics and mechanism
Authors: Bartoň Jaroslav , Kárpátyová Angela 
Published: April 2003

AbstractThe effect of 2,2′‐azoisobutyronitrile (AIBN) on the kinetics and mechanism of emulsion polymerization of butyl methacrylate was studied in the presence of anionic emulsifier disodium dodecylphenoxybenzene disulfonate (Dowfax® 2A1) at 60°C. The ratio between the proportion of the polymerization in monomer droplets and that of the polymerization in the aqueous phase was determined for the overall initial rate of butyl methacrylate polymerization in the region of the increasing polymerization rate (interval I). Using the model of polymerization in discrete particles, the portion of the polymerization in monomer droplets with a diameter of 100 nm in the overall polymerization rate is 24,4%; the portion of the polymerization in the water phase is only 0,022% for a concentration of Dowfax® 2A1 of 5 · 10−2 mol · dm−3, and 60,4% and 0,054% for a Dowfax® 2A1 concentration of 1 · 10−2 mol · dm−3. The exponent of the emulsifier concentration in the equation for the polymerization rate is 0,56 for interval I and 0,36 for interval II; the exponent for the concentration of AIBN over the conversion range between 0 and 30% is 0,34. For the proposed reaction mechanism it is assumed that 2‐cyanoisopropyl radicals, generated from AIBN in the water phase, are responsible for the initiation of polymerization in micelles swollen by monomer and in polymer/monomer particles. Polymer/monomer particles are formed also by co‐precipitation of oligomer radicals, which in turn are formed by polymerization of monomer molecules present in the water phase. Polymerization within monomer droplets has no significant influence on the course of emulsion polymerization.
Enzyme‐analogue built polymers, 22. Influence of the nature of the crosslinking agent on the performance of imprinted polymers in racemic resolution
Authors: Wulff Günter , Vietmeier Jürgen , Poll Heinz‐Günter 
Published: April 2003

AbstractThe effect of the nature of the crosslinking agents in template‐imprinted polymers on the selectivity during racemic resolution was investigated. Ethylene dimethacrylate was found to be the best crosslinking agent. The highest selectivity was achieved with polymers which have been prepared with 70‐95% crosslinking agent in the monomeric mixture. A new optically active crosslinking agent, 1,4;3,6‐dianhydro‐D‐sorbitol 2,5‐dimethacrylate, was synthesized and was used for the preparation of template‐imprinted polymers. Interpenetrating networks consisting of two different crosslinking systems did not bring about any significant improvement in selectivity for racemic resolution. A strong temperature effect for racemic resolution was observed; an ethylene dimethacrylate‐crosslinked, template‐imprinted polymer showed an optimum selectivity at 75°C with a ratio of distribution coefficients of the D‐ and L‐isomers of α = 4,56 for the separation of the racemate of the template.
Enzyme‐analogue built polymers, 23. Influence of the structure of the binding sites on the selectivity for racemic resolution
Authors: Wulff Günter , Poll Heinz‐Günter 
Published: April 2003

AbstractThe influence of the structure of the binding sites in template‐imprinted polymers on the selectivity for racemic resolution was investigated, taking boronic acids as the binding sites. A number of different polymerizable boronic acids, possessing varying degrees of flexibility between the polymerizable double bond and the boron, were synthesized and were bound to the phenyl α‐D‐mannopyranoside template. After polymerizing to highly crosslinked polymers and splitting off the template, the selectivity for racemic resolution of the racemate of the template was investigated. An inverse relationship between the flexibility of the binding sites and the selectivity for racemic resolution was observed.
Synthesis of star and model network polymers from poly(tetrahydrofuran)s with azetidinium end groups and multifunctional carboxylates
Authors: Tezuka Yasuyuki , Goethals Eric J. 
Published: April 2003

AbstractStar polymers with 2, 3 and 4 branches were synthesized in coupling reactions of poly(tetrahydrofuran) [poly(THF)] containing an azetidinium ring as single end group with di‐, tri‐, and tetrafunctional carboxylates, respectively. The coupling reaction proceeded by simple precipitation of the star polymer by addition of the polymer to an aqueous solution containing an excess of the corresponding sodium carboxylate. Model networks with 3 and 4 branches were produced by the same technique using poly(THF) with two azetidinium rings as end groups and tri‐ and tetrafunctional carboxylates, respectively.
Polymers with pendant carbazolyl groups, 2. Synthesis and characterization of some novel liquid crystalline polysiloxanes
Authors: Lux Martin , Strohriegl Peter , Höcker Hartwig 
Published: April 2003

AbstractThe synthesis of the liquid crystalline polysiloxanes 8a‐c is reported. In these polymers carbazolyl groups are incorporated in the mesogenic units. 8a‐c were prepared from the Schiff's bases 7a‐c and poly(hydrogenmethylsiloxane) in a polymer analogous reaction. The liquid crystalline polymers were characterized by DSC and polarizing microscopy. The Schiff's bases 7a‐c are nematic, whereas the polysiloxanes 8a‐c exhibit smectic mesophases within a broad temperature range. Unfortunately, the polymers show no remarkable increase of conductivity upon illumination.
Acid and base functionalization of ethylene‐propylene rubbers, 1. Grafting of tertiary amino groups and “interpolymer” network formation
Authors: Immirzi Barbara , Lanzetta Nunzio , Laurienzo Paola , Maglio Giovanni , Malinconico Mario , Martuscelli Ezio , Palumbo Rosario 
Published: April 2003

AbstractBase functionalization of saturated ethylene‐propylene rubbers (EPR) was performed either by means of the radical grafting of 2‐(dimethylamino)ethyl methacrylate onto EPR or by the reaction of a succinic anhydride grafted EPR with N,N‐dimethylethylenediamine. Differences in the structure of the grafted molecules and in their thermal stability are also reported. An investigation is made on the reactivity of EPR having tertiary amino pendant groups toward acid functionalized EPR leading to gelation.
Über Abbaureaktionen bei der alkalischen Hydrolyse von Polyacrylsäureestern in Dimethylsulfoxid
Authors: Pasch Harald , Schulze Horst , Schulz Günter 
Published: April 2003

AbstractThe alkaline hydrolysis of some methyl methacrylate‐ethyl acrylate copolymers in alkaline dimethyl sulfoxide leads to products containing carboxyl groups and having molecular weights which are significantly lower than those of the original copolymers. Size exclusion chromatographic (SEC) investigations provide detailed information on the degree of degradation and the influence of hydrolysis rate on degradation. Comparing the reactivities of structural units it is assumed that the degradation reaction occurs at the ethyl acrylate units.
Effect of glass transition on catalytic activity of polymer‐anchored rhodium complexes
Authors: Uematsu Takayoshi , Nakazawa Yasuo , Akutsu Fumihiko , Shimazu Shogo , Miura Masatoshi 
Published: April 2003

AbstractA rhodium complex was anchored upon three types of phosphinated polystyrene which were crosslinked with divinylbenzene or ethylene dimethacrylate. Glass transitions were separately observed for the flexible polymer supports and their polymer‐anchored rhodium complex catalysts using differential scanning calorimetry. Discontinuous activity drops in the Arrhenius plot for the ethylene hydrogenation reaction were observed for these flexibe polymer catalysts, while, for the rhodium complex anchored on a highly crosslinked rigid polymer, neither glass transition nor such a discontinuity in the catalytic activity could be detected. This reversible activity drop is discussed in terms of changes in the stability and the coordination state of the ethylene complex influenced by the micro‐Brownian motion of the polymer network.
Structural studies of poly(1,2‐cyclohexene oxide) prepared with well‐defined organozinc compounds
Authors: Hasebe Yoshihiro , Tsuruta Teiji 
Published: April 2003

AbstractThree samples of poly(1,2‐cyclohexene oxide) were prepared with ZnEt2, (EtZnOMe)4, and [{MeOCH2CH(Me)OZnO(Me)CHCH2OMe}2 · {EtZnO(Me)CHCH2OMe}2] ([Zn‐MP]2,2), respectively, as initiator. Each polymer sample was treated with butyllithium to form various decomposition products having double bonds or hydroxyl groups as end groups. Two dimeric diols, were obtained from the decomposition products and were found to have isotactic (SSSS or RRRR) and syndiotactic (RRSS) structure, respectively. By comparison of the relative yield of the two dimeric diols from each sample with the relative intensity of the three major signals in their 1H NMR spectra, the latter were assigned to methine protons of isotactic, syndiotactic, and heterotactic triads (from downfield to upfield). It was found that most parts of the main chain of the polymer prepared with [Zn‐MP]2,2 were composed of syndiotactic triads, SSRRSS (or RRSSRR), while the polymer prepared with ZnEt2 or (EtZnOMe)4 contained syndiotactic and heterotactic triads in comparable amounts.
Advanced computerized evaluation of gel permeation chromatography results: Calibration and correction for peak broadening
Authors: Schröder Ulrich K. O. , Ebert Klaus H. 
Published: April 2003

AbstractAn advanced method for evaluating gel permeation chromatography (GPC) results is described. Based on a modified broad‐molecular‐weight standard calibration method the calibration curve for poly(p‐methylstyrene) (PPMS) is constructed with several narrow‐molecularweight polystyrene (PS) standards and 4 broad‐molecular‐weight PPMS samples (weight‐average molecular weight M̄w = 14000 to 450000). The molecular weight range is covered from that of the monomer up to several hundredthousands. A computer code is developed to correct the elution curves for axial dispersion by a personal computer (PC) in relatively short calculation times.
Morphologie makroporöser 4‐vinylpyridin/divinylbenzol‐copolymere
Authors: Janßen Jan Cornelis , Klein Joachim , Widdecke Hartmut 
Published: April 2003

AbstractMethods for the preparation of macroporous poly(4‐vinylpyridine/divinylbenzene) resins with very different structures are described and the process of polymerization is discussed. The resins were prepared by suspension polymerization. The divinylbenzene content was varied between 8 and 25 mol‐% and dioctyl phthalate, heptane, toluene, and mixtures of these solvents have been used as porogenic agents. The morphology of the resins was determined by mercury porosimetry, BET surface measurements, and electron scanning microscopy. By the use of aliphatic porogenic agents high pore diameters up to 9000 Å and surface areas of at least 17 m2/g resin were found whereas by the use of aromatic solvents like toluene resins of low pore size and surface areas up to 88 m2/g were obtained.
Dielectric properties of a combined main‐chain/side‐chain liquid‐crystalline polymer
Authors: Endres Bernhard W. , Wendorff Joachim H. , Reck Bernd , Ringsdorf Helmut 
Published: April 2003

AbstractThe dielectric relaxation properties of a combined main‐chain/side‐chain liquid‐crystalline polymer were investigated. It was found that the rotation of the side chain about the main chain (δ‐process) is not as strongly restricted as in side‐chain liquid‐crystalline polymers. This is attributed to the facts that the side chain is attached to the flexible spacer within the chain backbone and that the concentration of the side chains is comparatively small. Two low‐temperature relaxation processes were observed to occur in the glassy smectic and the crystalline state. They are attributed to intramolecular motions with in the mesogenic groups.
Synthesis and characterisation of poly(arylene sulfides), 6. Synthesis of block copoly(arylene sulfides)
Authors: Lovell Peter A. , Still Richard H. 
Published: April 2003

AbstractNovel ABA block copolymers of poly(1,4‐phenylene sulfide) (PPS(A)) and poly‐(2‐methyl‐1,4‐phenylene sulfide) (PMPS(B)) were synthesised from bis(4‐bromophenyl) sulfone (BBS) by sequential reaction with copper(I) 4‐bromo‐2‐methylbenzenethiolate (CBMT) and copper(I) 4‐bromobenzenethiolate (CBT). PPS, PMPS and PPS/PMPS random copolymers were also prepared to aid block copolymer characterisation. Polymer fractions were studied by hot‐stage microscopy to evaluate melting ranges, and molar masses were computed from bromine end‐group concentrations and from gel permeation chromatography studies. Compositional analyses were made by IR and 1H NMR spectroscopy leading to confirmation of the block copolymer structure and to evaluation of the degrees of polymerisation of the individual blocks.
Synthesis and characterisation of poly(arylene sulfides), 7. Transitional behavior of random and block copoly(arylene sulfides)
Authors: Lovell Peter A. , Still Richard H. 
Published: April 2003

AbstractDifferential scanning calorimetry was used to evaluate first and second order transition temperatures and % crystallinity of poly(1,4‐phenylene sulfide) (PPS), poly(2‐methyl‐1,4‐phenylene sulfide) (PMPS), their blends and random and block copolymers comprising thio‐1,4‐phenylene and thio‐2‐methyl‐1,4‐phenylene units. Results are discussed in terms of the miscibility of PPS and PMPS in the melt phase and disruption of the crystallisation of PPS units by PMPS units. Microphase separation in the block copolymers was shown to be dominated by crystallisation of the PPS blocks. The application of Krause's microphase separation theory to prediction of the transitional behaviour of the block copolymers is critically discussed.