bluuebunny/crossref_metadata_2025_split huggingface dataset:
Catalysis by copper complexes of syndiotactic homo‐ and copolymers of Nα‐protected 2‐methylallyl histidinate
Authors: Frey Johann‐Wilhelm , Klein Jakob , Klesper Ernst 
Published: April 2003

AbstractThe syndiotactic Nα‐protected poly(2‐methylallyl L‐histidinate) and the corresponding copolymers, poly[(2‐methylallyl alcohol)‐s‐co‐(2‐methylallyl L‐histidinate)], were complexed with different Cu(II) compounds and used as catalysts for the aerobic oxidation of hydroquinone to quinone. The apparent first order rate constants were one to two orders of magnitude larger for the Cu(II)‐complexed homo‐ and copolymers than for the Cu(II) compounds or the polymers alone, or for the model compound in its complexed or uncomplexed state.
Radius of gyration and hydrodynamic radius of branched polystyrenes in cyclohexane and toluene measured by static and dynamic light scattering
Authors: Murayama Mitsumoto , Okada Mamoru , Fukutomi Takashi , Nose Takuhei 
Published: April 2003

AbstractThe radius of gyration Rg and the hydrodynamic radius Rh for branched (denoted by subscript b) and linear (1) polystyrenes of different molecular weights were measured both in theta‐ and good solvents. The ratios gg ≡ Rgb/Rgl, gh ≡ Rhb/Rhl, and Rh/Rg were calculated and compared with theoretical predictions based on the Kurata‐Fukatsu theory and its extention to good solvent systems. The following observations were made: gg/ggΘ < gh/ghΘ < 1 and (Rh/Rg)1 < (Rh/Rg)b < 1. The expansion coefficients αg and αh are reduced by the incorporation of branching. Theoretical predictions are qualitatively consistent with these results. The second virial coefficient of branched polymers has a larger molecular‐weight dependence than that of linear polymers, which was explained by a smaller molecular‐weight dependence of Rg. The penetration function of branched polymers is about three times as large as that of linear polymers.
Characterization of hydroxy‐terminated polybutadienes by 13C NMR
Authors: Kanakavel Meenakshisundaram 
Published: April 2003

AbstractProton noise‐decoupled 13C NMR spectra were used to investigated the sequence distribution of isomeric triads in hydroxy‐terminated polybutadienes (HTPB). The population of nine transcentred and seven cis‐centred triads was calculated from the integrated intensities in the olefinic region. The population of v\documentclass{article}\pagestyle{empty}\begin{document}$\underline{{\rm tc}}$\end{document}/t, c/t\documentclass{article}\pagestyle{empty}\begin{document}$\underline{{\rm tv}}$\end{document} and t\documentclass{article}\pagestyle{empty}\begin{document}$\underline{{\rm tc}}$\end{document}/t triads is higher for HTPB obtained by free radical polymerization than for anionically obtained HTPB. Quantitative data concerning their diad and triad composition were also derived from intensities of the peaks in the aliphatic region. The microstructure calculated from the sum of the population of cis‐ and trans‐centred triads in the olefinic region agrees well with the microstructure computed from the diads and triads of cis(c), trans(t) and vinyl(v) units in the aliphatic region. The methylene and methine carbons in vvv sequences are sensitive to tacticity.
Estimation of the 0th‐order diffusion constant of polydisperse polymer in dilute solution and its application to the “diffusion constant versus molecular weight relationship”
Authors: Okabe Masaru , Ukaji Takeshi 
Published: April 2003

AbstractA useful method for determining the “diffusion constant vs. molecular weight relationship” for monodisperse polymers is proposed using polydisperse polymers. According to this method, the diffusion constant vs. molecular weight relationship can be established if the 0th‐order diffusion constants are plotted against the 0th‐order molecular weights. The method was tested experimentally by using polydisperse polystyrenes in ethyl methyl ketone at 25°C and in cyclohexane at 35°C (theta‐state). It was ascertained that the diffusion constant vs. molecular weight relationship was well established without any effect of molecular weight distribution even if the polymers were polydisperse.
Kreuzinterferenzen im röntgenkleinwinkeldiagramm von gedehnten segmentierten PU‐elastomeren
Authors: Bonart Richard , Bötzl Franz , Schmid Johann 
Published: April 2003

AbstractSegmented polyurethane elastomers, when stretched for the first time from the isotropic state, show cross interferences in small angle X‐ray scattering, characterized by an orientation angle which is practically independent of the stretching ratio. This is due to a slip mechanism of plate‐like hard‐segment domains combined with an adjustment of the chain cross sections of hard and soft segments. Furthermore, partial chain folding and, following the hypothesis of force strands, an inhomogeneous deformation process has to be taken into account.
Calixarenes, 19. Studies of the formation of calixarenes via condensation of p‐alkylphenols and formaldehyde
Authors: Dhawan Balram , Chen Shou‐I , Gutsche C. David 
Published: April 2003

AbstractThe base‐induced reaction of p‐alkyl substituted phenols with formaldehyde yields oligomers which, in some cases, are cyclic [1,1,1,1]‐metacyclophames known as calixarenes. The present work attempts to provide insight into the mechanism of calixarene formation by studying various facets of the reaction, including the effect on the product distribution (i.e. cyclic tetramer, cyclic pentamer, cyclic hexamer, cyclic heptamer, and cyclic octamer) of (a) reactant ratios, temperature, solvent, and cation, (b) starting oligomer (i.e. monohydroxymethyl or dihydroxymethyl monomer phenol, dimer phenol, trimer phenol, or tetramer phenol), and (c) p‐alkyl group of the starting phenol. Product analyses were carried out by isolation and TLC methods in some cases and by HPLC methods in others. On the basis of the data that have been obtained it is postulated that (a) the calix[8]arenes are the product of kinetic control and are formed via a hemicalix[8]arene arising from intermolecular association between a pair of hydroxymethylated linear tetramers, (b) the calix[6]arenes are the product, in part, of template control and may be formed via a hemicalix[6]arene anion arising from intermolecular association between a pair of hemicalixarene anions from hydroxymethylated linear trimers, and (c) the calix[4]arenes are the product of thermodynamic control and can be formed via ring contraction of the calix[8]arenes and the calix[6]arenes.
Cationic graft copolymerization of tetrahydrofuran with partially α‐brominated polystyrene
Authors: Cai Gang‐feng , Yan De‐yue 
Published: April 2003

AbstractPartially α‐brominated polystyrene was first prepared from commercial polystyrene and N‐bromosuccinimide by the Wohl‐Ziegler reaction. It was treated with silver perchlorate to initiate cationic graft copolymerization with tetrahydrofuran leading to polystyrene‐graft‐polytetrahydrofuran. The influence of reaction time, reaction temperature, initial concentrations of silver perchlorate and partially α‐brominated polystyrene, etc., on the graft polymerization was studied. It partially α‐brominated polystyrene with a bromination degree of 5–15% was used, a leather‐like graft copolymer was obtained with a high grafting efficiency at or below 0°C.
Polymerizable amphiphiles, 3. Polymerization of micellized 1‐O‐3‐(4‐vinylphenyl)propyl‐β‐D‐glucopyranose
Authors: Nagai Katsutoshi , Elias Hans‐Georg 
Published: April 2003

Abstract1‐O‐3‐(4‐Vinylphenyl)propyl‐β‐D‐glucopyranose (1) was polymerized in organic solvents and in aqueous solutions above and below the critical micelle concentration by three different free‐radical initiators: 2,2′‐azoisobutyronitrile (AIBN), dipotassium peroxodisulfate (K2S2O8), and 2‐(phenylazothio)naphthalene (ATE). The polymerization is self‐accelerating in dilute aqueous solutions, regardless of whether oil‐soluble or water‐soluble initiators were used. Size exclusion chromatography was employed to monitor the change of molar masses, molar mass distributions, and conversions with time. The polymerization kinetics was also followed by UV spectroscopy. The polymerization by ATE led to polymerized micelles (P‐mers) under preservation of the degree of micellization. The polymerization by K2S2O8 and AIBN, on the other hand, resulted in the polymerization of bigger micelles (R‐mers) beside a small amount of polymerized P‐micelles.
Facilitated transport of alkali metal picrates through acetylcellulose blend membranes containing synthetic macrolides
Authors: Atsumi Miharu , Okada Masahiko , Sumitomo Hiroshi 
Published: April 2003

AbstractPermeation of alkali metal picrates through acetylcellulose membranes containing synthetic macrolides (4 and 5) was examined in tris‐buffer solutions (pH 7,8) to evaluate the effectiveness of the macrolides as ion carriers. The macrolides 4 and 5 are 20‐ and 25‐membered macrocyclic oligoesters, respectively, consisting of alternating tetrahydropyran ring and ester moieties, which were prepared by cationic ring‐opening polymerization of 6,8‐dioxabicyclo[3.2.1]octan‐7‐one (1). Ion permeability through the blend membranes increased with increasing macrolide content. The macrolide 5 facilitated ion transport more effectively than the macrolide 4. Dependence of ion permeability on solute concentration in a source phase was analyzed by using Lineweaver‐Burk's equation, and it was revealed that the ion transport through the blend membranes obeyed kinetics of a Michaelis‐Menten type. Ion selectivity sequence for the permeation of alkali metal picrates through the membrane containing 5 was, although not remarkable, Na+ > K+ > Cs+, in sharp contrast to the previously reported ion selectivity sequence for the transport mediated by the macrolides through liquid organic membranes.
Synthesis of new polyamides having in‐chain trans‐1,2‐dicarbazolylcyclobutane units and their spectroscopic properties
Authors: Subramaniam Prema , Sasakawa Tomoyoshi , Ikeda Tomiki , Tazuke Shigeo 
Published: April 2003

AbstractNew polyamides having in‐chain trans‐1,2‐dicarbazolylcyclobutane (DCZB) units were prepared. Fluorescence studies have shown that the fluorescence quantum yields of these polyamides are rather low in comparison with those of DCZB alone and vinyl polymers containing the DCZB units. Furthermore, time‐resolved measurements have revealed that the fluorescence decay of these polyamides can, in general, be analyzed by a triple exponential decay with life times of 1–2 ns (≈20%), 5–6 ns (≈35%), and 12–14 ns (≈45%).
Dynamic viscoelasticity and anomalous thermal behaviour of concentrated agarose gels
Authors: Watase Mineo , Nishinari Katsuyoshi 
Published: April 2003

AbstractDynamic viscoelasticity measurements, and differential scanning calorimetry (DSC) were carried out, in order to examine the gelling mechanism of concentrated solutions of agarose with two different molecular weights. The dynamic elastic modulus of the gels increases up to about 35°C and then decreases with increasing temperature. The DSC endothermic peak temperature Tm accompanying the gel‐sol transition was almost independent of the concentration of the gel, which is quite different from the behaviour of many other thermo‐reversible gels. Tm is shifted to higher temperatures with increasing molecular weight of agarose. The endothermic enthalpy was proportional to the concentration of gels for both fractions. A peak characteristic of crystalline material was observed in the X‐ray diffraction pattern of an agarose gel (concentration 15 wt.‐%).
Der interferenzeffekt von gestreckten markoff‐ketten erster ordnung, 2. Einkettenrechnung unter berücksichtigung der atomistischen comonomerstrukturen
Authors: Bonart Richard 
Published: April 2003

AbstractThe interference function of liquid‐crystalline A/B‐block‐copolymers is given. The function is restricted to a one‐chain calculation, i.e. packing effects of neighbouring chains are neglected. It refers to fully elongated first‐order Markoff‐chains with A‐ and B‐sequences, the lengths of which are controlled by the transition probabilities pAA and pBB for A‐A and B‐B steps. Combinations of an A‐ and a B‐sequence each are considered as formal super‐comonomers which follow randomly after each other. Thus, a statistical super‐copolymer not of A‐ and B‐monomers but of A‐ and B‐sequences comes into existence, obeying the interference function as given by Blackwell, Biswas, and Bonart in an earlier paper. Whereas only the reference points of the A‐ and B‐comonomers were considered in the first part of the paper, also the atomistic structures of the comonomers are now taken into account. The result renders the possibility to analyse the chain statistics of liquid‐crystalline copolymers as will be shown in following papers.
Morphology of nylon 6 spherulites in bulk
Authors: Galeski Andrzej , Argon Ali S. , Cohen Robert E. 
Published: April 2003

AbstractA method of obtaining good quality ultrathin sections from nylon 6 bulk samples has been developed by using a special embedding technique and cryo‐ultramicrotomy. The morphologies of nylon 6 processed by compression and injection molding and of reaction injection molded nylon 6 were studied in ultrathin sections of bulk samples by means of transmission electron microscopy. It was established that the spherulites of nylon 6 in bulk are built up from long flat ribbonlike lamellae. The thickness of the lamellae is in the range 50–60 Å. The width varies from 150 to 600 Å and depends on the type of nylon 6 and the method of processing. The length of the lamellae is relatively large approaching spherulite radii, extending often from the point of their origin up to the spherulite borders. Three or four neighboring lamellae within spherulites usually show similar orientation of their flat faces and form domains which can easily be mistaken for fibrils in light microscopy or low resolution electron microscopy.
Crystallization, melting and morphology of poly(hexamethylene sulfide)
Authors: Sánchez Angeles , Marco Carlos , Fatou José G. , Bello Antonio 
Published: April 2003

AbstractPoly(hexamethylene sulfide) fractions, ranging in molecular weight from 4600 to 20000, were isothermally crystallized from the melt state in the temperature range 50–70°C. The dependence of the melting temperature on the crystallization temperature was analyzed in experiments involving low and high levels of crystallinity. The equilibrium melting temperature corresponds to 366 K and the enthalpy of fusion was found to be 40,5 cal/g (= 170 J/g). The isothermal overall crystallization rates were analyzed using dilatometric and calorimetric techniques. The Avrami exponent is an integral value, n = 3, and the crystallinity varies with increasing molecular weight from 65% to 55%. The morphology is spherulitic and it was found that the growth rate is linear in the whole range of crystallization temperatures. The temperature coefficient of the crystallization was analyzed using nucleation theory, and comparison between dilatometric and growth data revealed that the overall rate and growth rate‐temperature coefficients are approximately equal.
Thermotropic polyesters, copolyesters and model compounds based on terephthalic acid and 4,4′‐alkylenediphenols
Authors: Fradet Alain , Heitz Walter 
Published: April 2003

AbstractMain chain thermotropic polyesters 1a and 1b and random copolyesters 1ab, based on terephthalic acid and 4,4′‐hexamethylenediphenol (5a) or 4,4′‐decamethylenediphenol (5b) were synthesized in good yields by a solution reaction in presence of benzenesulfonyl chloride. A mechanism is discussed. Low molar mass models 4a and 4b and oligomers 2a, 2b, 3a and 3b, with the same mesogenic unit and end groups comparable to the spacers used in polymers 1, were synthesized and their liquid‐crystalline properties compared to those of polymers. Models with at least two mesogenic units and polymers exhibit both smectic and nematic mesophases. Increasing spacer length decreases dramatically the stability of the nematic mesophases, but lowers only slightly the melting points. The phase diagram for random copolyesters 1ab were determined by DSC. Broad endotherms with overlapping multiple peaks were found for most of the copolymers. Monomeric units of 1a and 1b cocrystallize in 1ab, which leads only to slight melting point depression. The variations of nematic‐isotropic transition versus composition of copolymers are linear, while the smectic phase stability appreciably decreases.
Syntheses and characterization of terminally functionalized polypropylenes
Authors: Doi Yoshiharu , Hizal Gürkan , Soga Kazuo 
Published: April 2003

AbstractFunctional polypropylenes having vinyl, phenyl or hydroxyl groups at the chain end were prepared by adding common monomers as butadiene, styrene and 1,2‐epoxypropane, respectively, at −78°C during the living coordination polymerization of propene with a soluble V(acac)3/Al(C2H5)2Cl catalyst. In addition, polypropylene with hydroxyl functions was prepared by an alternative method based on the hydrogenation of a polypropylene containing aldehyde functions with LiAlH4. These new types of terminally functionalized polypropylenes were well‐characterized by 1H NMR analysis.
Hydrolysis of phenyl esters in cyclodextrin‐polymer systems
Authors: Seo Toshihiro , Kajihara Taketoshi , Iijima Toshiro 
Published: April 2003

AbstractThe catalytic hydrolysis of phenyl esters in systems containing ß‐cyclodextrin (ß‐CD) and polyelectrolytes was investigated. Poly(methacrylic acid) was found to exhibit an inhibition effect on the hydrolysis, while poly(sodium styrenesulfonate) (NaPSS) shows a pronounced acceleration effect on the hydrolysis: the larger the molecular weight and the lower the degree of substitution, the greater is the acceleration effect. On the other hand, sodium ethylbenzenesulfonate and sodium dodecylbenzenesulfonate inhibit the reaction. The acceleration of the reaction in presence of NaPSS is attributed to the concentration of ß‐CD and the substrate esters near to the chain of the macromolecule, through inclusion effects and hydrophobic interactions.
Une méthode d'immobilisation d'anticorps par liaisons covalentes sur nylon 66. Application en test immunoenzymatique
Authors: Couturier Roger , Ville Albert , Perrin Bernard , Favre‐Bonvin Guy 
Published: April 2003

AbstractA new method of immobilization of low‐molecular‐weight compounds or antibodies on nylon 66 was developed. Secondary amide groups of nylon 66 were converted into secondary imidate groups by O‐alkylation with sulfuric acid and methanol. The methoxycarbonimidoyl groups react with amino compounds to produce stable amidine links. Antibodies and several low‐molecular‐weight compounds (amino acids) were immobilized by covalent linkage on nylon balls. Fixed antibodies were used in solid phase enzyme linked immunoassay, i.e. applied for the detection of K99+ Escherichia Coli in calves.
Anionic living polymerization of β‐propiolactone initiated with crowned potassium methacrylate: Macromonomers and their copolymers with butyl acrylate
Authors: Sosnowski Stanisław , Stomkowski Stanisław , Penczek Stanisław , Arkhipovich Georgii N. , Kazanskii Konstantin S. 
Published: April 2003

AbstractThe polymerization of β‐propiolactone (βPL) with crowned K+ counterion has been shown previously to be a living process. This behaviour was used to prepare macromonomers of poly(βPL) with the methacryloyl reactive group. Poly(βPL) is known to be a crystalline polymer; thus, copolymers of poly(βPL) macromonomers with butyl acrylate gave graft copolymers with properties stemming from this ability. Selected mechanical properties of the copolymers are close to those of acrylic rubbers reinforced with fillers.
Synthesis of unsaturated oligoesters containing maleoyl and/or fumaroyl units via the intermediate isourea salts
Authors: Joos Betina , Schmidts Beate , Funke Werner 
Published: April 2003

AbstractUnsaturated oligoesters with carboxylic acid end groups were prepared from maleic and/or fumaric acid and 1,6‐hexanediol. The oligomers with molar masses between 700 and 1 100 were synthesized from smaller ester units via the corresponding isoureas, applying the carbodiimide method. Three oligoesters with uniform molar masses and chemical structures were obtained in excellent yields. They were characterized by gel permeation chromatography, infrared spectroscopic analysis, elemental analysis and by determination of their acid numbers.
Three‐phase carboxylation reactions of poly(chloromethylstyrene) beads with sodium nitrite
Authors: Howang K. T. , Takahashi M. , Iwamoto K. , Senō M. 
Published: April 2003

AbstractThe formation of carboxylic acid groups (carboxyl + ester groups) was found in a threephase reaction of crosslinked poly(chloromethylstyrene) beads with an excess amount of sodium nitrite in immiscible solvents of benzene and water with tetrabutylammonium bromide as a phase transfer catalyst (PTC), and the dependence of carboxylic acid yield on the experimental conditions was studied. The product contains hydroxyl groups and ester bonds besides carboxyl groups. It was tentatively considered that the carboxyl groups are produced by direct oxidation of chloromethylstyrene groups by nitrous anions. Nitrous anions do not only act as a nucleophile but also as an oxidative reagent in this case.
Compatibilité de polymères porteurs de groupements amides tertiaires avec le poly(difluoro‐1,1 éthylène). Etude par enthalpimétrie différentielle
Authors: Galin Monique 
Published: April 2003

AbstractThe miscibility of poly(1,1‐difluoroethylene) (1) with poly(N‐vinyl‐2‐pyrrolidone) poly(N‐methyl‐N‐vinylacetamide) and poly(N,N‐dimethylacrylamide), containingtert‐amido groups, was investigated by differential scanning calorimetry. Amorphous homogeneous blends were obtained whenever the weight fractions of polymer1is less than 0,7. The dependence of the single glass transition temperature (Tg) versus composition may be readily analyzed either through the Gordon‐Taylor equation (high values of thekparameter, suggesting strong specific interactions between the homopolymers) or by means of the Couchman relation (no adjustable parameter). The broadening of the glass transition range and the variation of the increment of specific heat atTgfor the blends are discussed.
Electrochemistry of thin polypyrrole films
Authors: Wernet Wolfgang , Wegner Gerhard 
Published: April 2003

AbstractThin polypyrrole (PP) films with octanesulfonate, dodecylsulfate and polystyrenesulfonate counterions were electrochemically switched between the conducting oxidized and the insulating neutral state in various electrolytes. In propionitrile under rigorous exclusion of oxygen and water PP can be cycled more than a thousand times without an appreciable decrease in electrochemical capacity. In an aqueous medium this process becomes irreversible after less than a hundred scans, the effect being strongly influenced by the pH of the electrolyte. Furthermore a pronounced dependence of the available charge upon the time (t5) between subsequent scans is found. It is known that treatment of PP films by a base leads to a remarkable decrease in conductivity. A mechanism which explains the loss of conductivity is proposed, in addition the possible occurrences of irreversible chemical changes as side reactions during electrochemical cycling is discussed.
A study on the states of ethyl benzoate and TiCl4 in MgCl2‐supported high‐yield catalysts
Authors: Terano Minoru , Kataoka Takuo , Keii Tominaga 
Published: April 2003

AbstractThe states of ethyl benzoate (EB) and TiCl4 in the primary types of MgCl2‐supported catalysts were studied by thermogravimetry/differential thermal analysis (TG‐DTA) in combination with other methods. The results obtained by all experiments indicate that TiCl4 and EB in the MgCl2‐supported high‐yield catalysts interact only with MgCl2, leaving no vacant sites on TiCl4.