bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions of human hemoglobin with high‐molecular‐weight dextran sulfate and diethylaminoethyl dextran
Authors: Nguyen Trong Q.
Published: April 2003

The binding of hemoglobin with high molecular weight dextran sulfate and diethylaminoethyl (DEAE) dextran was studied by turbidimetry, viscosimetry, ultrafiltration and oxygen affinity measurements. The results indicate that a complex is formed between hemoglobin and the charged dextrans through salt bridges. This complexation can lead to precipitation if the ionization degree of hemoglobin is high enough to develop an extensive neutralization of the charges of polyionic dextrans. At the pH value near to the isoelectric point, complexation still occurs, probably through salt bridges between the polyelectrolytes and the ionized sites of opposite charge on the hemoglobin molecule, but the complexes remain soluble in solution. Binding appears to be stronger for the hemoglobin‐dextran sulfate compounds than for the hemoglobin‐DEAE dextran compounds. The oxygen affinity of hemoglobin is greatly decreased in the presence of dextran sulfate, indicating a stabilization of the deoxyhemoglobin with respect to the oxyhemoglobin.
Anionic ring‐opening polymerization of 2,2‐dimethyltrimethylene carbonate
Authors: Keul Helmut , Bächer Reinhard , Höcker Hartwig
Published: April 2003

The anionic ring‐opening polymerization of 2,2‐dimethyltrimethylene carbonate in solution with sec‐butyllithium as initiator was found to result under suitable conditions in a bimodal molecular weight distribution, vic. cyclic oligomers and a high‐molecular‐weight polymer. The concentration of cyclic oligomers approaches that of a ring chain equilibrium. In the kinetically controlled regime high polymer yields were obtained. Optimum reaction conditions for a polymer yield of 85 – 95% are a temperature of −10°C, an initial monomer concentration of 10 weight‐% and toluene as solvent. In THF the ring chain equilibrium is achieved readily. The ceiling temperature was determined to be ≈ 30°C. The homopolymer was characterized by spectroscopic, thermoanalytical and viscosity measurements. A high degree of crystallinity was observed.
Effect of the number of crystallizable blocks on the lamellar crystalline structure of block copolymers from poly(4‐tert‐butylstyrene) and poly(ethylene oxide)
Authors: Gervais Monique , Gallot Bernard , Jérome Robert , Teyssié Philippe
Published: April 2003

Linear block copolymers tBSEO with an amorphous block of poly(4‐tert‐butylstyrene) (PtBS) and a crystallizable block of poly(ethylene oxide) (PEO) as well as branched block copolymers tBS(EO)2 with two PEO chains linked at the same end of a PtBS block exhibit a lamellar liquid‐crystalline structure in the dry state as well as in the presence of a preferential solvent of the PtBS block. In this structure the crystallized chains are folded in two superposed layers. To investigate the effect of the number of the PEO blocks, a linear and a branched copolymer with identical relative molecular masses and copositions were studied by X‐ray diffraction and differential scanning calorimetry. It was shown that the melting temperature, the degree of crystallinity, and the number of folds of the PEO chains are higher for the linear copolymer than for the branched one.
Deuteron NMR study of molecular order and motion of the mesogenic side groups in liquid‐crystalline polymers
Authors: Pschorn Uwe , Spiess Hans Wolfgang , Hisgen Bernd , Ringsdorf Helmut
Published: April 2003

The molecular order and mobility of two liquid‐crystalline polyacrylates with phenyl benzoate moieties as mesogenic side groups and (CH2)m spacers (m = 2 and m = 6) were investigated by pulsed 2H NMR. The mesogenic side groups were isotopically labelled at the terminal phenylene ring. In the glassy state the orientational distribution function was characterized from the angular dependence of the 2H NMR line shape of samples macroscopically ordered in their nematic phase by the 8,4 T magnetic field of an NMR spectrometer. It was found to be Gaussian with widths of ± 18,5° and ± 10,5° for the m = 2 frozen nematic and m = 6 frozen smectic system, respectively. The phenylene rings undergo 180° jumps about their local C2‐axes in the glassy state. The time‐scale of this process, however, was found not to be uniform. Instead, the analysis of 2H NMR line shapes and their intensities as a function of temperature yielded a log‐Gaussian distribution with correlation times characteristic of amorphous solids, 2,2 versus 2,5 decades in width and mean activation energy ĒA = 42 versus 47 kJ/mol for the m = 2 and m = 6 system, respectively. The correlation times for the centre of the distribution agree with those obtained by dielectric relaxation measurements of the same systems, suggesting that reorientation of the whole mesogenic group is detected via the phenylene rings.
Phase‐transfer catalytic activity of phosphonium salts bound to microporous polystyrene resins by long spacer chains
Authors: Tomoi Masao , Kori Nobuo , Kakiuchi Hiroshi
Published: April 2003

Supports of polystyrene with long spacers were prepared by bromoalkylation of microporous, crosslinked polystyrene resins with ω‐bromoalkenes using CF3SO3H as catalyst. The dependence of the phase‐transfer catalytic activity of phosphonium salts bound to the polystyrene resins by long spacer chains, derived from the bromoalkylated polystyrene resins, on the percentage of ring substitution, on the degree of crosslinking, and on spacer‐chain length was studied. The high activity of the catalyst with long spacer chains was explained by the increased reactivity of the active site, induced by the increased lipophilicity of the catalyst, and by the facilitated ion exchange which was brought about by an increased distance between the active site and the polymer backbone.
Chemical modification of polydienes, 3. Copolymers with polytetrahydrofuran by grafting‐from butadiene polymers
Authors: Cameron G. Gordon , Qureshi M. Younus , Rudin Alfred
Published: April 2003

Polybutadienes of various microstructures and some butadiene copolymers were epoxidised to low levels (<1 mol‐%) with m‐chloroperbenzoic acid. The epoxide groups functioned as initiation sites for a “grafting‐from polymerization” of tetrahydrofuran (THF) catalysed by BF3. By conducting the reaction in dilute THF solution ([Monomeric unit] < 0,3 mol · 1−1) with a large excess of BF3 over epoxide groups, gel formation was avoided. The conversion of THF was less than 2% and the copolymers contained from 10 to 50% polytetrahydrofuran (PTHF) comprising graft chains of molar mass up to 43000 g · mol−1. The relative rate of grafting tended to decrease as the content of trans‐1,4 units in the backbone polymer increased, and, unusually, there was a small increase in volume during the graft copolymerization. The graft copolymers had a two‐phase morphology consisting of amorphous rubber and crystallites of PTHF. The latter function as physical crosslinks which break down above the melting point of PTHF, so that the materials behave as thermoplastic elastomers.
Paramagnetic amphiphiles
Authors: Dulog Lothar , Ritter Ralf , Hauser Manfred , Brosig Stefan
Published: April 2003

Surface active N‐oxyl radicals containing aliphatic chains were prepared from palmitinic, stearic and oleic acid chlorides by reaction with 4‐hydroxy‐(or‐4‐amino‐) 2,2,6,6‐tetramethyl‐piperidine or its N‐oxyl. In the former case the resulting esters or amides were subsequently oxidized. A dioleyl ester (3b) was prepared analogously from 2,2,6,6‐tetramethyl‐4‐bis(2‐hydroxyethyl)aminopiperidine. Surface tension data of aqueous solutions were determined and micelle formation was confirmed by light transmission measurements. The size of the water droplets in hexane solution of the dioleoyl derivative was estimated by the fluorescence spectroscopic method to 4,62 nm.
Block polymers obtained by means of anionic polymerization. Polystyrene‐block‐poly(ε‐caprolactone) and polystyrene‐block‐poly(2,3‐dimethyltrimethylene carbonate)
Authors: Keul Helmut , Höcker Hartwig
Published: April 2003

The anionic ring‐opening polymerization of ε‐caprolactone and 2,2‐dimethyltrimethylene carbonate in toluene as solvent with polystyryllithium or lithium polystyrylethoxide resp. lithium polystyrylmethoxide as initiators, results in the formation of the corresponding block polymers as major products, beside small amounts of homopolymer. The block copolymers were isolated chromatographically from the mixture and analyzed spectroscopically.
Thermo‐rétraction et orientation moléculaire du poly(téréphtalate d'éthylène) soumis a une déformation uniaxiale homogène et plastique
Authors: Rietsch François
Published: April 2003

A study of molecular orientation in drawn and shrunk poly(ethylene terephthalate) was undertaken at 80°C and 120°C for samples drawn at (i) 80°C (homogeneous deformation) and (ii) two‐stage drawing: a homogeneous pre‐orientation at 80°C, followed by cold drawing at 20°C. The results (birefringence, residual shrinkage ratio, crystallinity) are discussed in terms of molecular disorientation in the noncrystalline region which occurs upon the shrinkage process.
The role of polymer chain tacticity of cyclolinear polydecaorganocyclohexasiloxanes in the formation of a mesomorphic state
Authors: Makarova Natalia N. , Godovsky Yuli K. , Kuzmin Nikolai N.
Published: April 2003

New trans‐ and cis‐polydecaorganocyclohexasiloxanes of intermediate tacticity between transtactic and cistactic and atactic were prepared by heterofunctional polycondensation of the trans‐ and cis‐isomers of 2,8‐dichlorodecaorganocyclohexasiloxanes with the corresponding dihydroxydecaorganocyclohexasiloxanes. Composition and molecular structure of polymers obtained were determined by means of elemental analysis, IR and 29Si NMR spectroscopy, intrinsic viscosity, and molecular weight analysis. Using DSC, X‐ray and optical analysis the influence of chain tacticity on the formation of a mesophase and on the crystalline state was determined. All the polymers studied exhibit a mesophase state the temperature interval of which is dependent on chain tacticity.
Etude par diffusion de la lumière du système ternaire solvant/polydiméthylsiloxane/poly(méthacrylate de méthyle)
Authors: Anasagasti Marisol , Katime Issa , Strazielle Claude
Published: April 2003

The ternary system solvent (1)/polydimethylsiloxane (2)/poly(methyl methacrylate) (3) was investigated by light scattering. First the measurements were realized on mixtures containing low‐molecular‐weight polydimethylsiloxane: M2 ≪ M3. In a second step, high and comparable molecular weights of both polymers were chosen for the measurements. The thermodynamic interaction parameter χ23 was determined from light scattering data (spinodal) and demixtion curves as a function of concentration and molecular weight of the polymers. Also the variation of the angular repartition of the scattered light was studied and the results were compared with calculated values.
A composite model for the thermal conductivity of semicrystalline polymers
Authors: Biswas Prabir K. , Sengupta Shyamal , Basu Asok N.
Published: April 2003

A phenomenological model is proposed which considers the polymer as an aggregate of units. The units are composed of two distinct phases — amorphous and crystalline. The thermal conductivity of a unit is calculated in terms of those of its constituents. In the undrawn state these units are distributed randomly, and the isotropic thermal conductivity of the bulk results. The development of strong anisotropy in thermal conductivity is explained in terms of the preferred orientation of these units. The structural features of this model are similar to those employed for the interpretation of the mechanical properties. The change in orientation of the units was deduced from the experimental data of birefringence. Finally, the results obtained from the composite model for several semicrystalline polymers are compared with the experimental data and other existing calculations. The model is found to give a fair overall description of the thermal conductivity in the cases of polypropylene, polyoxymethylene, low and high density polyethylene, and polychlorotrifluoroethylene.
Bis(2‐chloroethyl)amine bound to copolymers of N‐(2‐hydroxypropyl)methacrylamide and methacryloylated oligopeptides via biodegradable bonds
Authors: Ringsdorf Helmut , Schmidt Brigitta , Ulbrich Karel
Published: April 2003

Drug carriers were prepared by combining oligopeptidic sequences with synthetic polymeric chains. Soluble copolymers of N‐(2‐hydroxypropyl)methacrylamide (HPMA) were synthesized containing oligopeptidic side chains terminating in a drug model (p‐nitroaniline). The susceptibility of these oligopeptidic sequences to degradation on incubation with lysosomal enzymes and human serum was evaluated by monitoring the p‐nitroaniline liberation. It was shown that the drug model can be attached to the polymer carrier by means of an oligopeptidic spacer stable in blood serum and degradable after the polymer has been in contact with intracellular lysosomal enzymes. The studied polymer carriers were used for binding an anticancer drug, bis(2‐chloroethyl)amine.
Anionic polymerization of fluorine‐containing vinyl monomers, 6. Polymerizations of fluoroalkyl acrylates and methacrylates initiated by organoaluminium compounds
Authors: Narita Tadashi , Hagiwara Tokio , Hamana Hiroshi , Miyasaka Takehiko , Wakayama Akira , Hotta Tetsuo
Published: April 2003

The anionic polymerizations of 2,2,2‐trifluoroethyl acrylate (1a), 2,2,2‐trifluoroethyl methacrylate (1b), 2,2,2‐trifluoro‐1‐trifluoromethylethyl acrylate (2a), and 2,2,2‐trifluoro‐1‐trifluoromethylethyl methacrylate (2b) were examined with triethylaluminium and diethylaluminium active methylene chelate compounds as initiators. 2b was polymerized with triethylaluminium. Diethyl(ethyl cyanoacetato)aluminium was found to produce polymers of 1a and 1b. Diethyl(acetylacetonato)aluminium and diethyl (dimethyl malonato)aluminium, however, show low reactivity towards these four monomers. The resulting polymers show unimodal molecular weight distribution with number‐average molecular weights of 104−105, measured by GPC. The initiation reaction and the copolymerization reactivity with styrene support the anionic polymerization mechanism.
Polymeric insecticides, 2. Synthesis and bioevaluation of polymeric controlled release systems with covalently bound N2‐(4‐chloro‐2‐methylphenyl)‐N1,N1‐dimethylformamidine (chlordimeform) analogues
Authors: Lohmann Dieter , d'Hondt Christian
Published: April 2003

Polymerizable N2‐(4‐chloro‐2‐methylphenyl)‐N1‐methylformamidine derivatives of (N‐demethyl‐chlordimeform) (2) were prepared, bearing either 4‐vinylbenzyloxy‐ or 2‐methacryloyloxyethoxycarbamoyl groups (5 and 7), and in addition, a triazatriphosphorine derivartive of 2 (8). The carbamoyl groups and the P‐N linkages in the monomers, respectively, were specifically designed to release the insecticide 2 under the particular microenvironmental conditions on cotton leaves by hydrolytic cleaveage, triggered by the pH 8–10 of the leaf surface. Biossaying experiments using larvae of the Egyptian Cotton Leafworm (Spodoptera littoralis) on cotton plants confirmed methacrylate 7 as the only compound with sufficient bioactivity. Corresponding homo‐ and copolymers of 7, containing covalently bound pendent moieties of 2, showed advantageous physiochemical properties with regard to improved efficiency and reduced environmental and handling risks in conventional foliar applications. The biological data suggest that the release rates of the active agent from the polymers vary significantly, depending on the hydrophilicity of the comonomers and the type of formulation used.
Kinetics of the amine salt initiated polymerization of ε‐caprolactam with regard to tetrahedral intermediates
Authors: Bertalan György , Nagy Tibor T. , Rusznák István , Tőke László , Anna Péter , Marosi György , Domján Pál
Published: April 2003

A computer simulation of the kinetics of the amine salt initiated lactam polymerization was carried out using an extended kinetic model. In the reaction scheme the formation and relatively fast two‐way reaction of a tetrahedral intermediate, as well as the role of the acid in its formation were incorporated. On the basis of the extended kinetic model the calculated lactam conversion and the concentration of N‐terminal groups, respectively, have been found to be in good agreement with the experimental values for both the amine salt initiated and the hydrolytic lactam polymerization. The numerical values of rate and equilibrium constants are given.
Crystallization kinetics of 1,4‐trans‐polyisoprene, 2. Polymer‐diluent mixtures
Authors: Chaturvedi Prakash N.
Published: April 2003

Four 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

Enantioselective 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

The 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

1‐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

The 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

2‐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

Syntheses 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

The 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

The 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

The 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

Star 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

The 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

Base 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

The 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

A 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

Three 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

An 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

Methods 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

The 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

Novel 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

Differential 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.
Synthesis and characterisation of poly(arylene sulfides), 9. Optimisation of the solvent composition for solution polymerisation of copper(I) 4‐bromobenzenethiolate at atmospheric pressure and structural investigations of low molar mass poly(1,4‐phenylene sulfide)
Authors: Lovell Peter A. , Still Richard H.
Published: April 2003

Solution polymerisation of copper(I) 4‐bromobenzenethiolate (CBT) was effected at atmospheric pressure using a range of quinoline/pyridine solvent mixtures. Yields of poly(1,4‐phenylene sulfide) (PPS) were evaluated and PPS fractionated into toluene soluble (TS) and 1‐chloronaphthalene soluble (CNS) material. The fractions were characterised by end‐group analysis, viscometry and differential scanning calorimetry. The yield of CNS PPS is optimum for solvent mixtures comprising 70–80 vol.‐% quinoline, whereas the molar mass of this fraction is at a maximum for 95 vol.‐% quinoline. Results are discussed in terms of the effects of reaction temperature, complexing of CBT by quinoline and pyridine, and copper(I) bromide‐catalysed debromination. A low molar mass TS PPS fraction prepared in pyridine was subjected to detailed structural analysis by IR, 1H NMR and Raman spectroscopy. Evidence is presented to show that this material contains disulfide linkages and that thiol end‐groupings are absent. These results are discussed relative to possible structures for poly(arylene sulfides). The relevance of this observation to high molar mass samples of PPS and their chain extension and degradative behaviour is also discussed.
Polymérisation de thiirannes différemment substitués à l'aide du système chiral ZnEt2/(S)‐dihydroxy‐2,2′ binaphtyl‐1,1′, 1. Stéréoélectivité de la polymérisation
Authors: Sepulchre Maurice
Published: April 2003

Differently substituted thiiranes were polymerized using an atropoisomeric chiral initiator: ZnEt2/(S)‐2,2′‐dihydroxy‐1,1′‐binaphthyl (DHBN) (mole ratio 1/1). It was observed that high stereoelectivities are obtained with monomers bearing small alkyl substituents and that the resolution efficiency of the initiator decreases as the bulkiness of the substituent increases. From the comparison of the results obtained with another initiator system, ZnEt2/(R)‐3,3‐dimethyl‐1,2‐butanediol (DMBD) (mole ratio 1/1), the use of ZnEt2/(S)‐DHBN could be shown to be more suitable for the polymerization of thiiranes with linear alkyl substituents. Contrary to the case of polymerization initiated by the system ZnEt2/(R)‐DMBD, the polymerization reaction of thiiranes with ZnEt2/(S)‐DHBN was usually accompanied by the production of the corresponding olefins in various amounts.
Studies in electroactive polymers, 2. Soluble polyacetylene: A new synthetic route
Authors: Stowell Jonathan A. , Amass Allan J. , Beevers Martin S. , Farren Trevor R.
Published: April 2003

Polyacetylene‐block‐polystyrene was synthesized via an anionic‐to‐metathesis catalysis. The polymers obtained were characterized by UV/visible spectroscopy, IR spectroscopy and gel permeation chromatography.
Quantitative evaluation of soluble polymeric photosensitizers, 4. Trans‐cis isomerization of stilbene photosensitized by polymerbound o‐ and p‐benzyloxybenzaldehyde
Authors: Martinez‐Utrilla Roberto , Catalina Fernando , Sastre Roberto
Published: April 2003

The grafting of o‐ and p‐benzyloxybenzaldehyde onto linear chloromethylated polystyrene is described. The resulting soluble polymeric photosensitizers and their model compounds, o‐ and p‐(p‐isopropylbenzyloxy)benzaldehyde, were tested as triplet energy donors against trans‐stilbene in benzene solution. Irradiation of the ortho‐compounds gives rise to a transformation which has been tentatively attributed to an intramolecular photocyclization. Stern‐Volmer constants for the photostable para‐compounds were determined. Results for both types of compounds show that the sensitizer efficiency diminishes when it is bound to the polymer.
Viscosity behaviour of macro‐ring polystyrene in solution
Authors: Qian Renyuan , Cao Ti
Published: April 2003

A simple treatment for the intrinsic viscosity data of a flexible macro‐ring polymer in solution is proposed. The viscosity behaviour of dilute solutions of a macro‐ring with molar mass M is considered to be equal to that of a linear chain with molar mass λT·M, where the factor λT is found to be close to 0,5. Thus the ratio of the intrinsic viscosity of the macro‐ring polymer and that of the corresponding (same molar mass) linear chain polymer gr ≡ [η]r/[η]l = λ with α = exponent of Mark‐Houwink equation gives the correct excluded volume effect on the value of gr as verified by the dilute solution viscosity behaviour of a macro‐ring polystyrene sample of weight‐average molecular weight Mw = 2,72·105 and theta‐ and thermodynamically good solvents.
Photo‐oxydation de polyéther‐bloc‐polyamides, 3. Propriétés des hydroperoxydes dans les homopolym`res de polyéthers correspondants
Authors: Gauvin Pascal , Lemaire Jacques , Sallet Daniel
Published: April 2003

The photooxidation of poly(tetramethylene glycol) (PTMG), poly(propylene glycol) (PPG) and poly(ethylene glycol) (PEG) was studied at 60°C applying wavelengths longer than 300 nm. Hydroperoxy groups were found to accumulate in high photostationary concentration in PTMG and were decomposed essentially into formate groups. Hydroperoxides were observed in low photostationary concentration in PEG and PPG. Decomposition of the PPG hydroperoxides into formate groups showed that hydroperoxidation occurs, surprisingly, at the secondary carbon atom of the propylene glycol monomeric unit, rather than at the tertiary carbon. These results account for the large variation in the properties of hydroperoxides observed throughout the photooxidation of polyether‐block‐polyamides of various composition.
Polymerization of N‐phenylmaleimide with organozinc compounds as initiators
Authors: Hagiwara Tokio , Sato Junji , Hamana Hiroshi , Narita Tadashi
Published: April 2003

The polymerization of N‐phenylmaleimide (N‐PMI) was carried out with organozinc compounds as initiators. Within the initiators examined [Zn(OCH3)2·(C2H5ZnOCH3)6] gave the highest yield of poly(N‐PMI). The polymer yield increased rapidly at the early stage of the polymerization reaction. The poly(N‐PMI) produced shows a unimodal molecular weight distribution in the high‐molecular‐weight region and two components in the oligomeric region in GPC. 1H NMR and 13C NMR spectra suggest an addition polymerization without any remarkable side reactions. The results of the copolymerization with styrene and of the polymerization in nitrobenzene suggest an ionic polymerization mechanism.
Poly(α‐amino acid)‐immobilized polymer adsorbents for optical resolution, 2. Effect of crosslinking degree of the support resin on the resolution efficiency
Authors: Kiniwa Hideaki , Doi Yuka , Nishikaji Takashi , Ogata Naoya
Published: April 2003

Polymer adsorbents for chromatographic optical resolution were synthesized by grafting poly(N5‐benzyl‐L‐glutamine‐co‐γ‐benzyl L‐glutamyl) onto cross‐linked polystyrene beads. The effects of the crosslinking degree (1,5%, 9%, 30%) and the porosity of the polystyrene matrix on the resolution efficiency of the adsorbent were investigated. Similar resolution efficiencies were observed on 1,5% cross‐linked gel (non‐porous) and 9% cross‐linked porous adsorbents, while a decline in the efficiency was observed on 30% cross‐linked porous adsorbent. Studies of transmission electron micrographs of these adsorbent clearly showed the effect of degree of crosslinking on the distribution manner of the incorporated poly(α‐amino acid). At a degree of 30%, clustered incorporation occurs mainly on the pore surface and not within the cross‐linked polymer matrix. Such incorporation manners are also suggested by the swelling properties of the adsorbents. Pore volumes, pore radii, and specific surface areas of the adsorbents were also measured. It was observed that uniform incorporation of poly(α‐amino acid) derives a higher resolution efficiency of the adsorbent.
Poly(α‐amino acid)‐immobilized polymer adsorbents for optical resolution, 3. A total chromatographic optical resolution on poly(N5‐benzyl‐L‐glutamine)‐immobilized resin
Authors: Kiniwa Hideaki , Doi Yuka , Nishikaji Takashi , Ogata Naoya
Published: April 2003

A 9% cross‐linked porous polystyrene resin (10–15 μm) incorporating poly(γ‐methyl L‐glutamate) (PMLG) was synthesized, and the grafted PMLG was then converted into poly(N5‐benzyl‐L‐glutamine) (PBLGN). In this newly developed procedure, almost quantitative conversion of PMLG to PBLGN is achieved. The obtained adsorbent for liquid chromatography demonstrated a total optical resolution of (RS)‐5‐isopropylhydantion. Experimental evidence demonstrated that the degree of polymerization (DP) of the incorporated poly(α‐amino acid) is a critical variable. At DP = 2, no resolution was accomplished, whereas At DP = 14 or 36, base line resolutions were achieved. Other fundamental factors, such as the concentration of the immobilized PBLGN, the column temperature and the eluent composition, which affect the resolution efficiency, were also evaluated.