bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics of radical polymerization of tolyl methacrylates
Authors: Vrhovac Ljubica , Veličković Jovan 
Published: April 2003

AbstractThe kinetics of radical polymerization of tolyl methacrylates, initiated with 2,2′‐azodiisobutyronitrile and dibenzoyl peroxide were studied using dilatometric and gravimetric techniques. The initial rates of polymerization depend on the position of the methyl subsitution in the aromatic ring. With both initiators the initial rates of polymerization in the range within 50 and 70°C increase in the order: ortho < meta < para substitution. The overall rate constants and activation energies were determined. The different rates observed are discussed in terms of steric effects, monomer constitution, and other factors which might affect the reactivity of the radical propagation.
Styrene‐divinylbenzene copolymers, 3. Revisited IR analysis
Authors: Bartholin Michel , Boissier Giselle , Dubois Joelle 
Published: April 2003

AbstractA critical analysis of the styrene‐divinylbenzene resin infra‐red spectra was made using previous works and new results. A method for the determination of pendent double bonds and also crosslinking degree and composition of the resin is drawn. A few examples of application are given.
Temperature effect on the stereoelective polymerization of methylthiirane in homogeneous phase
Authors: Dumas Philippe , Sigwalt Pierre , Guérin Philippe 
Published: April 2003

AbstractChiral cadmium thiolates of cysteine with cyclohexyl or (−)menthyl ester groups were prepared and compared with similar compounds (with isopropyl or methyl ester groups) as initiators for stereospecific polymerization of methylthiirane in homogeneous phase. The resulting polymers are highly isotactic and in all cases stereoelection can be reversed with a small change in polymerization temperature. This temperature effect permitted to differentiate two stages in the polymerization corresponding to the formation of a precursor and to that of a high polymer, respectively.
On the temperature dependence of interdiffusion coefficients for the cellodextrins
Authors: Amu Thomas C. 
Published: April 2003

AbstractInterdiffusion coefficients at infinite dilution were measured for the cellodextrins (glucose to cellohexaose) in aqueous solutions at 25 and 35°C using the modified Rayleigh interference optics. Diffusion data were also obtained for glucose in DMSO and formamide at 25, 30, 35, and 45°C. The experimental results are discussed with due regards to effects resulting from solute‐solvent interactions and also hydration of these oligomers.
A convenient method for the preparation of a highyl active MgCl2‐supported TiCl3 catalyst for the polymerization of propylene
Authors: Soga Kazuo , Terano Minoru 
Published: April 2003

AbstractA highly dispersed MgCl2‐supported TiCl3 catalyst was conveniently prepared by treating the complex of TiCl3 · 3 C5H5N with AlEt2Cl in the presence of MgCl2. The catalyst combined with AlEt3 showed a very high activity for the polymerization of propylene, and gave a polymer with considerably high isotacticity. The catalyst displayed a sharp ESR signal with a g‐value of 1,94, which is identical with that of the ground H‐grade TiCl3.
Telechelics 6. Oligostyrenes by radical polymerization
Authors: Konter Wolfgang , Bömer Bruno , Köhler Karl‐Heinz , Heitz Walter 
Published: April 2003

AbstractStyrene polymerized by AIBN as initiator results in telechelic α,ω‐bis(1‐cyano‐1‐methylethyl)oligostyrenes (1). The functionality, fCN, was found to be 1,99 ± 0,05 in the molecular weight range up to 2000 and the Mw/Mn‐values were found to be < 1,5 after complete consumption of the initiator. Using methyl 2,2′‐azoisobutyrate as initiator, oligostyrenes with two ester endgroups were obtained. The conversion of styrene was limited by “dead end” conditions as described by Tobolsky. The efficiency was 0,9 under the preparative conditions used. The cyano endgroups were converted into amino endgroups by hydrogenation and into carboxyl endgroups by hydrolysis. Telechelic α,ω‐bis(2‐isocyanato‐1,1‐dimethylethyl)‐ and α,ω‐bis(1‐isocyanato‐1‐methylethyl)oligostyrenes 4 and 6 were obtained from the amino product 2 by the phosgene method and from the carboxyl product 3 by the Weinstock/Curtius reaction, respectively. Connecting these telechelic styrene blocks by a polyreaction results in polymers in the 20 000 – 50 000 molecular weight range.
Preparation of polycations by polymerizing biscations and the conductivity of their TCNQ salts
Authors: Watanabe Masayoshi , Kamiya Tamotsu , Goto Kuniyuki , Matsubara Noriaki , Tsuchikura Akira , Shinohara Isao 
Published: April 2003

AbstractThe conductivity of 7,7,8,8‐tetracyanoquinodimethane (TCNQ) salts of biscations and polycations was investigated in dependence of the cation structures. The biscations, which were considered to be a model unit of polycations, were prepared by the Menshutkin reaction of aromatic amines, such as pyridine and quinoline, with α,ω‐dibromoalkanes. The polycations were synthesized by polymerizing bifunctional biscations bearing two amino groups with diisocyanates. The conductivity of the biscation‐TCNQ complex salts was mainly influenced by the interval between N+ atoms and the polarizability of the biscations. Biscations which had an optimum interval between N+ atoms and high polarizability were effective to obtain high conductive TCNQ salts. The TCNQ complex salts of polycations containing such biscation parts showed similar conductivity as the corresponding biscation‐TCNQ complex salts. It is suggested that the TCNQ molecules, under the influence of the biscation parts, dominated the conductivity of the polycation‐TCNQ complex salts.
Asymmetric‐selective polymerization of (R,S)‐α‐methylbenzyl acrylate initiated with Grignard reagent/(‐‐)‐sparteine and its modified systems
Authors: Okamoto Yoshio , Gamaike Hisataka , Yuki Heimei 
Published: April 2003

AbstractAsymmetric‐selective (or stereoelective) polymerization of racemic α‐methylbenzyl acrylate (2a) was studied with Grignard reagent/(–)‐sparteine and its modified catalyst system in toluene. All catalyst svstems polymerized preferentially the (R)‐monomer over the (S)‐monomer. The Grignard reagent/(–)‐sparteine system showed very low activity and gave the polymer only in a few per cent yield at −78°C. The addition of secondary amines such as piperidine and diethylamine to the catalyst system improved not only the activity but also the selectivity. The optical purity of the polymer initially formed with the cyclohexylmagnesium bromide/(–)‐sparteine/diethylamine system at − 78°C was 84%, and at about 80% polymer yield almost optically pure monomer was recovered. Asymmetric selectivity decreased with an increase of temperature. The dyad tacticity of the polymer was determined by 1H NMR spectroscopy. There was no clear correlation between the selectivity and tacticity. The role of the amines in the catalyst systems was investigated by 1H NMR spectroscopy.
Limites de solubilité des polyacrylamides partiellement hydrolysés en présence d'ions divalents
Authors: Schwartz Thierry , François Jeanne 
Published: April 2003

AbstractThe limits of solubility of hydrolyzed polyacrylamide in aqueous solution containing divalent cations is studied by turbidimetry. The stability is very poor in the presence of Ca++ and Ba++ and is better with Mg++ and Mn++. Conductivity and density measurements show that Ca++ and Ba++ are trapped without dehydration in intra‐and intermolecular bridges between two carboxylic groups of the polymer. Light scattering and viscosity studies allowed to propose a model according to which for polymer concentrations, Cp, lower than concentration of chain overlapping Cp* these cations induce intramolecular coil‐globule transition, and for Cp > Cp*, there are aggregates of globules by intermolecular bridges.
Flow properties of ethylene/vinyl acetate copolymers
Authors: Iruín Juan J. , Guzmán Gonzalo M. , Ansorena Javier 
Published: April 2003

AbstractA series of linear and branched fractions of an ethylene/vinyl acetate (EVA) copolymer is characterized by viscometry and gel permeation chromatography (GPC) exclusively. Characterization results are applied to the study of the influence of branching on flow properties of concentrated solutions of EVA fractions. Newtonian viscosity‐concentration‐molecular weight relationships are obtained for both linear and branched samples. Graessley's theory of entanglements for linear polymers is tested with a set of fractions. Experimental flow curves come out to be independent of the linear or branched nature of the samples.
Mechanism of the short chain branching in low density polyethylene
Authors: Stoiljkovich D. , Jovanovich S. 
Published: April 2003

AbstractIn this paper the validity of the well‐known Roedel's “back‐biting” mechanism is questioned. It is shown that number and type of branches depend on the degree of order (entropy) of compressed ethylene molecules. A new mechanism for the short chain branching in low density polyethylene is proposed, based on the effect of the supermolecular species in compressed ethylene in this reaction. An equation for calculation of the number of branches for ethylene polymerization in a wide range of temperature (−5 to + 200°C) and pressure (40 to 7000 atm) is given.
Feasibility of the light scattering method to characterize composition heterogeneities of copolymers
Authors: Tanaka Takeshi , Omoto Mitsuru , Inagaki Hiroshi 
Published: April 2003

AbstractFeasibility of light scattering as a method to characterize the composition heterogeneities of copolymers is examined with special reference to those measurements which are made in an isorefractive solvent, i.e., a solvent giving zero refractive index incrementvfor the copolymer. It is established theoretically and experimentally that the concentration dependence in the Zimm plot for an isorefractive system is almost absent, irrespective of the thermodynamic properties of the solvent employed. In addition, the error to which determination of the heterogeneity parameterQis subject due to inaccuracy invis minimum whenvis zero. By virtue of these facts,Qmay be determined with higher precision in an isorefractive solvent than in any other solvents. Under optimum conditions, it seems possible to determineQwith sufficient precision, ifQ⪆ 1·103andQ/Mw⪆ 2·10−3. These values are about an order of magnitude lower than those generally believed to be the applicability limits of the light scattering method.
Polymerization of methyl methacrylate with phenylmagnesium bromide — stereoregularity, molecular weight distribution and polymerization mechanism —
Authors: Matsuzaki Kei , Tanaka Hiroo , Kanai Taiichi 
Published: April 2003

AbstractThe stereoregularity and molecular weight distribution of poly(methylmethacrylate)s prepared with phenylmagnesium bromide or diphenylmagnesium as catalyst in tetrahydrofuran/toluene mixed solvents were investigated in detail. Some of the polymers were fractionated according to molecular weight or by adsorption with silical gel and the stereoregularities of the fractions were determined. An eneidic mechanism of propropagation was proposed based on the experimental results.1H NMR spectroscopy of deuterated phenylmagnesium bromide and of its reaction with methyl methacrylate indicated that an eneidic mechanism resulted from a Schlenk type equilibrium, which is shifted to the diphenylmagnesium species at low temperatures and in nonpolar solvents.
Synthèse de monoalcools et de monoacides chlorofluorés par télomérisation avec des telogènes chlorofluorés
Authors: Boutevin Bernard , Hugon Jean‐Pierre , Pietrasanta Yves 
Published: April 2003

AbstractTelomerizations of chlorofluorinated telogens CF3CCl3 and
\documentclass{article}\pagestyle{empty}\begin{document}$${\rm Cl\rlap{--} (CFCl \hbox{---} CF}_{\rm 2} {\rm \rlap{--} )}_{\rm n} {\rm CCl}_{\rm 3}$$\end{document} (1 ≤ n ≤ 4) with acrylic, allylic, and vinylic monomers were studied. With allyl alcohol and 2‐hydroxyethyl acrylate the corresponding fluorinated adducts 1 and 2 were obtained directly. Vinyl and allyl acetates led to the adducts 4a, b and 5a, b, respectively, which could be transformed into the corresponding acetals and alcohols. Telomerizations of methyl acrylate and methacrylate led to the fluorinated adducts 12a and b in the presence of copper chloride as catalyst or also with iron trichloride in the case of methyl methacrylate. By intramolecular elimination the methacrylate adducts were transformed into the lactons 13 and 14 and the acrylate adducts by reduction into the alcohols 1 and 2. The same reduction of the methacrylate adduct led to the 2,4,4‐trichloro‐5,5,5‐trifluoro‐2‐methyl‐1‐pentanol (15). Independent on the applied catalyst the telomerization of vinylacetic acid led to the monoaddition product, whereas in the case of methacrylic or acrylic acid the formation of monoadducts or higher addition products was found to depend on the catalyst.
Kinetik von copolymerisationen, 3. Geschwindigkeit der copolymerisation von N‐vinyl‐2‐pyrrolidon, styrol und methylmethacrylat
Authors: Braun Dietrich , Disselhoff Gabriele , Quella Ferdinand 
Published: April 2003

AbstractThe rates of the binary copolymerizations of N‐vinyl‐2‐pyrrolidone, styrene, and methyl methacrylate were investigated dilatometrically. In both systems with N‐vinyl‐2‐pyrrolidone as one of the two monomers the rate of copolymerization can be described by a theory of Abkin, whereas a theory of Russo and Munari can be applied to the behavior of the system styrene/methyl methacrylate.
Hochmolekulare produkte der kondensationspolymerisation von 4,4′‐methylendibenzaldehyd mit aliphatischen diaminen und polyfunktionellen isocyanaten
Authors: Tokarzewski Ludomir , Ragan‐Kusa Zenona 
Published: April 2003

AbstractPolymeric Schiff‐bases (3a–gand5a–c) were synthesized by condensation polymerization of 4,4′‐methylenedibenzaldehyde (1) with diamines2a–gor diisocyanates4a–c. In addition, a polymeric hydrazone was synthesized by reaction of the dioxime of1with the isocyanate4aand a crosslinked product was prepared from a trifunctional isocyanate and1. The products were characterized by elemental analysis and IR spectroscopy. Their physico‐chemical properties were determined and discussed as function of the number of CH2‐groups in the repeating units.
Polymer ester von sären des phosphors, 7. Polymerisation des 1‐oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.1]heptans
Authors: Gehrmann Thomas , Vogt Walter 
Published: April 2003

Abstract1‐Oxo‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.1]heptane is transformed in situ (prepared from trimethyl phosphite and glycerol) at −78°C in the presence of a trace of water into a crosslinked polymer containing constitutional repeating units with 5‐ and 6‐membered rings. The reaction with reagents containing hydroxyl groups (water, acetic acid, alcohol) leads to the degradation of the network with the formation of soluble fragments with Pn = 35–50. This reactivity and the possibility to obtain other derivatives from the fragments make this polymer a carrier for pharmacologically active polymers with the advantage of decomposing only into the innocuous components phosphoric acid and glycerol.
Chloro‐ionenes with ether bonds in the backbone chain. Determination of rate constants, orders of reaction and molecular weights
Authors: Bortel Edgar , Kochanowski Andrzej , Gozdecki Wiesław , Kozłowska Hanna 
Published: April 2003

AbstractThe subject of the investigation concerns chloro‐ionenes prepared from N,N,N′,N′‐tetramethylethylenediamine as well as N,N,N′,N′‐tetramethylhexamethylenediamine and from bis(2‐chloroethyl) ether as dihalide. The orders of reaction have been determined and were found to be n = 2 and n = 1,8, respectively. The established rate constants have a strong dependence on temperature due to the comparatively high energies of activation of ≈ 70 kJ/mol.–A reliable method has been worked out for determining the molecular weights of polyquaternaries with high charge densities in the backbone of the chain. The method is based on analytical ultracentrifugation according to the procedure of Archibald. From the investigations carried out, the conclusion can be drawn, that, in order to get proper results four extrapolations must be made. The measurements can be performed in the original solutions, in which the ionenes have been prepared, allowing the results to be obtained quickly by a computer.–The measured weight‐average molar masses of the ionenes were in the range between 1 500 and 4 000 g/mol.
Glass transition temperatures of copolymers (ethylene glycol/diethylene glycol) terephthalates
Authors: de la Campa Jose G. , Guzmán Julio , de Abajo Javier , Riande Evaristo 
Published: April 2003

AbstractCopolymers of (ethylene glycol/diethylene glycol) terephthalates were prepared by melt polycondensation. The values of the glass transition temperatures of the copolyesters, determined by dilatometry are in fair agreement with those predicted by the Fox equation. It was also found that the conformational entropy can be used to correlate equilibrium flexibility and glass transition behaviour of the copolyesters.
Internal mobility of PMMA in concentrated CDCl3 solutions, 2. 13C NMR spectra
Authors: Zajíček Jaroslav , Pivcová Hana , Schneider Bohdan 
Published: April 2003

AbstractThe 13C NMR relaxation parameters (T1, line widths and NOE factors) were measured and analyzed for two samples of atactic poly(methyl methacrylate) (PMMA) of molecular weight Mw 4,20·104 and 1,76.106 in CDCl3 solutions in the concentration range 11 to 54% (by weight) of polymer, at 297 and 323 K. By this analysis it was found that the backbone segmental motion of PMMA is spatially isotropic in the whole measured concentration range; the motion of the α‐CH3 group may be approximated by the double reorientation model; the motion of the ester CH3 group can be approximated by the isotropic model only at concentrations lower than 12%; in more concentrated solutions, a satisfactory approximation is obtained neither by the isotropic, nor by the double reorientation models. The reasons of this behaviour are discussed.
Cationic polymerization of thietanes initiated by trityl salts: Mechanism of the initiation reaction
Authors: Florquin Stefaan M. , Goethals Eric J. 
Published: April 2003

AbstractThe initiation reaction of the cationic polymerization of 3,3‐dimethylthietane by trityl hexafluoroantimonate occurs by a fast and quantitative direct addition of the trityl cation to the sulfide function thus producing the corresponding polymer with tritylthio head‐groups. In contrast with this mechanism, the reaction of the trityl salt with the non‐polymerizable sulfides tetrahydrothiophene and diethyl sulfide, leads to a slow hydride abstraction from the sulfide. With these sulfides an equilibrium [carbenium ion + sulfide ⇌ sulfonium ion] is also observed. At 25°C the association constants were found to be 2,27 and 0,096 1 · mol−1 for tetrahydrothiophene and diethyl sulfide, respectively (in CD2Cl2). The initiation mechanism by sulfonium ion formation is explained by the high reactivity of the formed four‐membered ring trityl sulfonium ion which disturbs the carbenium ion‐sulfonium ion equilibrium and ultimately leads to quantitative initiation.
Studies on carboxymethylated cellulose: Potentiometric titrations, 1
Authors: Trivedi Harikrishna C. , Patel Chiman K. , Patel Raman D. 
Published: April 2003

AbstractThe effect of polymer concentration and degree of substitution of carboxymethylated cellulose (CMC) on the dissociation constant was studied by potentiometry. The dissociation was found to be suppressed progressively either by decreasing [CMC] or increasing the degree of substitution of the CMC sample.
Polymerization of 2,4‐hexadiene with neodymium catalysts and characterization of the resulting polymers
Authors: Wang Fosong , Bolognesi Alberto , Immirzi Attilio , Porri Lido 
Published: April 2003

AbstractThe polymerization of (E,E)‐2,4‐hexadiene with the Al(C2H5)2Cl/Nd(OCOR)3/Al(iBu)3 system was examined. High molecular weight crystalline polymers were obtained in polymerizations carried out at room temperature or below. IR and NMR examination showed the polymers to consist predominantly of trans‐1,4 units. Degradative oxidation gave the racemic form of 2,3‐dimethylsuccinic acid, thus indicating a threo structure for the polymers. X‐ray analysis indicated that the polymers contain stereoregular sequences with a trans‐1,4‐threo‐diisotactic structure.
Synthesis and copolymerization of a polyamine macromer: Molecular design of a new functional graft copolymer
Authors: Nishimura Takao , Maeda Mizuo , Nitadori Yoshiaki , Tsuruta Teiji 
Published: April 2003

AbstractTo develop a new method for molecular design of functional polymers, polyamine macromers 4, 10, and 16 were synthesized by lithium alkylamide catalyzed polyaddition reactions of N,N'‐diethylethylenediamine (1), 1,4,10,13‐tetraoxa‐7,16‐diazacyclooctadecane (7), and piperazine (12) to 1,4‐divinylbenzene (2), respectively. Copolymerization of these macromers with styrene gave a new type of graft copolymers 6, 11, and 19, having polyamine grafts. Copolymerization data indicated that the length and number of graft chains could be controlled by adjusting the molecular weight of the macromer and its initial concentration in the copolymerization system. The crystallinity of 16, 19, and other macromers (17, 18) having piperazine units was discussed.
Stereoregularity of polystyrene derivatives, 1. Poly(methylstyrene)s and poly(methoxystyrene)s obtained with ziegler catalyst, cationic catalyst, or radical initiators
Authors: Kawamura Tokiji , Uryu Toshiyuki , Matsuzaki Kei 
Published: April 2003

AbstractThe 13C NMR spectra of methylstyrenes and methoxystyrenes and their polymers prepared with radical initiators, a Ziegler catalyst, or a cationic catalyst were measured. The spectra of the polymers were assigned by the chemical shifts of the monomers and gated‐decoupling method. The absorption of the aromatic C1 carbon of each polymer, which varied by the polymerization conditions, was assigned in terms of a pentad sequence assuming that the Bernoullian statistics holds for the polymerization of ring substituted styrenes. The stereoregularities calculated from C1 carbon absorptions were compared with those of polystyrenes obtained unter the same polymerization conditions. In the radical polymerization of ortho‐derivatives, where the substituent locates near the polymer backbone, high syndiotactic polymers (Pr = 0,80 − 0,83) were prepared. The effect of the substituent in para‐derivatives did not appear. On the other hand, random polymers were generally fromed by cationic polymerization regardless of the position and the type of the substituent.
Heteroaggregation of some dye‐pairs induced by organic and inorganic chromotropes
Authors: Pal M. K. , Ash Sudhir Kumar , Ghosh Bijan Kumar 
Published: April 2003

AbstractHeteroaggregations of the pair of cyanine dyes pinacyanol and thiacarbocyanine induced by the polyanions poly(potassium styrenesulfonate) and poly(potassium vinyl sulfate), and of methylene blue and acridine orange induced by mercuric chloride are described. In each case the characteristic of heteroaggregation, namely the enhancement of the metachromatic band of the partner dye having λmax at relatively shorter wavelength at the expense of the absorbance at the metachromatic band of the other dye, is reflected in the difference spectra. The dependence of the shape of the metachromatic band of pinacyanol on the nature of the polyanion inducing metachromasia is also reflected in the heteroaggregation of this dye and thiacarbocyanine induced by the two different polyanions. Mercuric chloride, though not a polyanion, also induces strong heteroaggregation of methylene blue and acridine orange.