bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical copolymerization of cyclic acetals derived from acrolein, 1. Copolymerization with acrylonitrile and α‐chloroacrylonitrile
Authors: Acosta José Luis , Mateo José Luis , Sastre Roberto 
Published: April 2003

AbstractCopolymerizations of 2‐vinyl‐1,3‐dioxane (1a), 5,5‐bis(hydroxymethyl)‐2‐vinyl‐1,3‐dioxane (1b), and 5,5‐dimethyl‐2‐vinyl‐1,3‐dioxane (1c) with acrylonitrile (AN) and α‐chloroacrylonitrile (CPAN) in N,N‐dimethylformamide (DMF) were investigated. For the AN(M1)/1a (M2), AN(M1)/1b (M2), and AN (M1)/1c (M2) pairs, the copolymerization parameters r1 are 5,2, 3,7, and 3,9, respectively. For the CPAN (M1)/1a (M2), CPAN (M1)/1b (M2), and CPAN (M1)/1c (M2) pairs, the r1 values are 7,95, 7,80, and 8,90, respectively. In all cases the r2 value is approximately zero. A clearly different influence of the monomer feed composition on the copolymerization rate is observed when the reaction takes place in the absence of solvent compared with that made in DMF. The explanation is related with the existence of associations between acrylonitrile or x‐acrylonitrile and the vinyl‐dioxane compound.
Solvent effect on the 13C NMR chemical shifts of meso and racemic 2,4‐dichloropentanes as the model compounds of poly(vinyl chloride)
Authors: Ando Isao , Kato Yoshiharu , Kondo Masahiro , Nishioka Atsuo 
Published: April 2003

AbstractThe 13C NMR chemical shifts of meso and racemic 2,4‐dichloropentanes as the model compounds of poly(vinyl chloride) in various solvents were observed, and were well interpreted theoretically by means of “solvaton”‐MO theory.The temperature dependence of the chemical shifts in pentachloroethane and dimethyl sulfoxide solutions were also well interpreted theoretically. Further, the similarity between these behaviours of the dimers and the polymer was discussed.
Small‐angle X‐ray scattering study on concentration dependence of polymer chain dimension
Authors: Hayashi Hisao , Hamada Fumiyuki , Nakajima Akio 
Published: April 2003

AbstractThe concentration dependence of polymer chain dimensions was studied by a new type of “tagged polymer method” in small‐angle X‐ray scattering. A small fraction of partially iodinated polystyrene, the tagged polymer, was mixed with polystyrene in toluene. From the excess scattering originated from the iodine, the radius of gyration of the polystyrene chain (Mv = 110000) was estimated at various concentrations. It was found that the chain dimension decreases first rapidly and then decreases gradually with increasing polymer concentration, and that, in the bulk, it coincides with the unperturbed chain dimension. The result was compared with theoretical predictions. The theories applicable to low concentrations could predict well the chain dimension upto mass concentrations of ca.0,1 g/cm3, while the theories applicable to higher concentrations could not predict well the chain dimension at high concentrations. The conformation of the polymer chain was also discussed. More compact conformations than a random coil as well as the bundle model were not supported by the results.
Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 5. Bestimmung der Masse der Einzelmoleküle und Aufnahme der Molekulargewichtsverteilung
Authors: Koszterszitz G. , Schulz G. V. 
Published: April 2003

AbstractA method is described for the determination of the molecular weight distribution (MWD) of various polymers from electron microscopy pictures of their molecules. It is shown, that the number of molecules needed to construct the distribution is between 200 and 300. Furthermore, with macroscopic density of the polymer and the volume determined by electron microscopy, the correct mass of a single molecule is obtained. The method is demonstrated for samples of polystyrene and poly(methyl methacrylate) and the results are compared with those of GPC‐measurements.
Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 2 Cinétique de la production d'éthylène
Authors: Thomassin Claude , Marchal Jean 
Published: April 2003

AbstractThe kinetics of the production of ethylene during the radiation induced autoxidation of poly(oxytetramethylene) were determined in chloroform solution at 25°C. It was found that the primary oxidative degradation of the polymer generating ethylene is part of a chain reaction process.
Réactions primaires de dégradation oxydante au cours de l'autoxydation du poly(oxytétraméthylène) à 25°C, 4 Discussion du schéma réactionnel
Authors: Thomassin Claude , Marchal Jean 
Published: April 2003

AbstractResults from previous publications of the series are interpreted and discussed in terms of a reaction scheme. Probabilities of the different non‐terminating reactions of α‐alkoxyalkylperoxy radicals during the autoxidation of solutions of poly(oxytetramethylene) 10−2 g cm−3 ≤ c ≤ 6.10−2 g cm−3 were determined as follows: for the H atom abstraction = 0,2–0,4, for the monomolecular decomposition (reference) = 1, and for the non‐terminating bimolecular reaction = 7–10.
Polymerisation of trioxane, 3. Kinetics of the reaction initiated by stannic chloride and phosphorous oxychloride
Authors: Raman Puthuruthy S. , Mahadevan Venkatanarayana 
Published: April 2003

AbstractThe kinetics of polymerisation of 1,3,5‐trioxane initiated by stannic chloride and phosphorous oxychloride were investigated in the solvents chlorobenzene, o‐dichlorobenzene, trichloroethylene, and tetrachloroethylene. With pure reactants no induction periods were observed. The kinetic and equilibrium parameters were evaluated.
Branching in free radical polymerization due to chain transfer, 2. Theory of the effect of polyfunctional transfer reagents
Authors: Ullisch Bernd , Burchard Walther 
Published: April 2003

AbstractPolyfunctional chain transfer reagents applied in free radical polymerization have two effects on the polymer molecular weight. As in the case of monofunctional regulators the chain length is reduced; the polyfunctionality of the transfer reagents causes, however, branching and thus an increase in molecular weight. A general theory is developed on the basis of Cascade Theory to describe the polymer structure in dependence on the monomer conversion. The theory takes advantage of the graph theoretical concept of digraphs by which the directed chain reaction can be properly represented. Analytic equations are derived for the weight average molecular weight Mw, z‐average mean square radius of gyration 〈S2〉z and the average particle scattering factor Pz(μ). Furthermore, a simple equation is given for the condition of gelation. Special concern is given to the formation of fractions of branched and linear polymers during the polymerization process. The derived equations are discussed in terms of kinetic constants known for polystyrene. Gelation is shown to be possible for a chain transfer constant of Ctr = 22 if the number of functional groups per transfer molecule exceeds at least a value of 7.
Branching in free radical polymerization due to chain transfer, 3. Polymerization of styrene in the presence of a tetrafunctional chain transfer agent
Authors: Ullisch Bernd , Burchard Walther 
Published: April 2003

AbstractThe effect of neopentanetetrayl tetrakis(2‐mercaptoacetate) on the molecular weight of polystyrene in free radical polymerization was studied. Polymerization experiments were carried out at three different concentrations of the tetrafunctional transfer reagent and were followed to monomer conversions up to β = 25%. For comparison, runs of polymerization were made without added transfer reagent and with a monofunctional 2‐mercaptoacetate, respectively. An apparent extent of branching was calculated from the molecular weights Mw obtained with the tetrafunctional and the monofunctional transfer reagent at fixed monomer conversion β and fixed concentration of reagent groups. This apparent extent of branching passes through a maximum at very small β and approaches the value 1 for large β. The decrease in the extent of branching is shown to be caused by the increasing fraction of linear polystyrene as the transfer reagent becomes exhausted.The data observed were compared with curves calculated from Cascade Theory with the known kinetic constants for polystyrene. A very good agreement between theory and experiment is observed at medium concentration of transfer groups. At smaller concentrations the increase in Mw is less than that predicted, and at large concentrations the increase in Mw is stronger than expected by theory. The deviations are attributed to negative and positive substitution effects.
A polymer model of lignin (D.H.P.) 13C selectively labelled at the benzylic positions: Synthesis and NMR study
Authors: Gagnaire Didier , Robert Danielle 
Published: April 2003

AbstractD.H.P. polymer model of Lignin was synthesized by enzymatic dehydrogenation of coniferyl alcohol enriched to 90% in 13C‐γ, on the benzylic position. On the 1H NMR spectrum recorded at 250 MHz, of the 13C labelled D.H.P., the study of the JCH‐γ couplings, made possible a precise assignment of proton signals. The 13C NMR spectra showed that the 13C‐γ carbon atom previously labelled in coniferyl alcohol was found in several sites in the polymer. Special NMR techniques like gate decoupling and selective proton irradiation were used together with the study of the chemical shifts, to make an assignment for the different 13C‐γ signals. C‐γ in carbonyl compounds like vanillin and vanillic acid, C‐γ vinylic atom like in coniferyl alcohol and cinnamaldehyde. C‐γ atom like in β5, ββ, βO4 dilignol units, and C‐γ atom involved in C‐γ benzyl ether bond in βO4 dimer were identified; the corresponding JCH–γ couplings of these C‐γ carbon atoms were determined.
Étude par spectroscopie ESR de la photodégradation de la poly(vinyl‐2 pyridine) et des copolymères vinyl‐2 pyridine/méthacrylate de méthyle
Authors: Quaegebeur Jean Pierre , Lablache‐Combier Alain , Chachaty Claude 
Published: April 2003

AbstractIrradiation of films of poly(2‐vinylpyridine), (poly[1‐(2‐pyridyl)ethylene]), and poly(4‐vinylpyridine), (poly[1‐(4‐pyridyl)ethylene]) at wavelengths λ > 300 nm gives rise to the corresponding vinylpyridinyl and azabenzyl radicals, the concentrations of which do not exceed 1015 spins/g. Introduction of naphthyl substituents into the polymer chain enhances appreciably the rate of radical formation from the copolymer. Irradiation at 254 nm of poly(methyl methacrylate), (PMMA) and its copolymers containing various amounts of 2‐vinylpyridine monomeric units shows that the presence of pyridyl groups along the chain of PMMA reduces the rate of accumulation of radicals. This result is ascribed to the screening effect of pyridine. The photoprotection by the pyridyl ring is likewise observed in the phenanthrene sensitized photolysis at λ > 300 nm of the various 2‐vinylpyridine/methyl methacrylate copolymers and its mechanism is discussed.
Reaktive Mikrogele, 7. Hydroxylgruppenhaltige Mikrogele
Authors: Seitz Ulrich 
Published: April 2003

AbstractThe pendant vinyl groups of reactive microgels prepared from 1,4‐divinylbenzene or divinylbenzene mixture were converted into hydroxyl groups by hydroboration with diborane. This reagent enters very fast into the network of the microgels and reacts with all vinyl groups.
Reaktion an Ziegler‐Natta‐Katalysatoren, 14. Anwendung der Olefin‐Metathese zum Nachweis einer Grignard‐Wurtz‐reaktion an hydrobromiertem 1,4‐Polybutadien
Authors: Kathan Wolfgang , Wedam Othmar A. , Hummel Klaus 
Published: April 2003

Abstract1,4‐Polybutadiene was partially hydrobrominated in the presence of AlBr3. A Grignard‐Wurtz‐reaction with phenylmagnesium bromide resulted in an exchange of the bromine atoms for phenyl groups. The polymers were degraded in an olefin metathesis reaction with 4‐octene using a WCl6/Sn(CH3)4 catalyst. The low molecular degradation products with bromine or phenyl substituents, resp., were separated by gas chromatography and identified by mass spectrometry.
Reaktion an Ziegler‐Natta‐Katalysatoren, 15. Einführung von halogenierten Aralkyl‐Gruppen in 1,4‐polybutadien und metathese‐abbau der modifizierten polymeren
Authors: Demel Hans , Hummel Klaus 
Published: April 2003

Abstract1,4‐Polybutadiene was partially aralkylated with halogenated alkylbenzenes (4‐fluorotoluene, 2‐, 3‐, and 4‐chlorotoluene, 4‐bromotoluene, 2‐chloro‐p‐xylene, 2,4‐dichlorotoluene, 3,4‐dichlorotoluene) and dicumyl peroxide. The modified polymers were investigated by IR‐spectroscopy and degraded by olefin metathesis reaction with 4‐octene. The degradation products were separated by gas chromatography and identified by mass spectrometry. In addition to the aralkylation methylation of the 1,4‐polybutadiene occurred.
Synthesis of 2,3,4‐tri‐O‐benzyl‐[1→6]‐α‐D‐glucopyranan and [1→6]‐α‐D‐glucopyranan with high molecular weight by polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose
Authors: Uryu Toshiyuki , Tachikawa Hiromichi , Ohaku Ken‐Ichi , Terui Keiko , Matsuzaki Kei 
Published: April 2003

AbstractThe polymerization mechanism of 1,6‐anhydro‐2,3,4‐tri‐O‐benzyl‐β‐D‐glucopyranose (1) was investigated in order to synthesize 2,3,4‐tri‐O‐benzyl‐[1→6]‐α‐D‐glucopyranan (2a) and [1→6]‐α‐D‐glucopyranan (2b) (dextran) with high molecular weight. It was found that the optimum polymerization time to obtain high molecular weights was 40min when the monomer was polymerized in methylene chloride at −60°C. Stereoregular 2a with a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ of 1800 (M̄n = 777000), which was about twice as high as the highest \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ previously reported, was obtained in 77% yield by polymerizing the monomer with 0.8 mole‐% PF5 as catalyst applying a monomer‐to‐solvent weight/volume ratio of 50%. 2a with a high molecular weight was debenzylated to give 2b with a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ of 446 (M̄n = 72300). The α‐stereospecificity and the solid state of the synthetic dextran were investigated by means of optical rotation, NMR spectroscopy, and X‐ray diffraction pattern.
Application of spin trapping technique to radical polymerization, 14. Initiation reaction of vinyl monomers with the tert‐butoxyl radical and evaluation of monomer reactivities
Authors: Sato Tsuneyuki , Otsu Takayuki 
Published: April 2003

AbstractThe initiation of various vinyl monomers with tert‐butoxyl radicals derived from the decomposition of di‐tert‐butyl peroxalate (DBPOX) was investigated by using the spin trapping technique with 2‐methyl‐2‐nitrosopropane (BNO), to detect and identify the intermediate radical species, and to evaluate the monomer reactivities toward the tert‐butoxyl radical. When the reaction of DBPOX with vinyl monomers, which have no α‐methyl group (CH2CH(X)), was carried out in the presence of BNO at room temperature, the propagating radical 1 ((H3C)3COCH2CHX) was trapped as its nitroxyl radical. However, in the cases of using α‐methylvinyl monomers (CH2CH(X)CH3), such as methyl methacrylate and methacrylonitrile, two kinds of radicals, 6 ((H3C)3COCH2C(X)(CH3), similar to 1) and 8 (CH2CH(X)CH2), were trapped as corresponding nitroxyl radicals. The coupling constants of the nitroxyls obtained from 1 and 6 were determined and discussed on the basis of their structure. When these reactions were performed in a reference solvent, p‐xylene, the above radicals, 1 (or 6) and/or 8, together with the p‐tolylmethyl radical (2), were trapped as their nitroxyls. From the ESR peak areas the relative reactivities of vinyl monomers toward the tert‐butoxyl radical were evaluated and found to depend not only on the polar nature, but also on the resonance effect of the substituents. In α‐methylvinyl monomers such as methyl methacrylate, the hydrogen‐abstraction from the α‐methyl group by the tert‐butoxyl radical was important.
Analysis of carbon‐13 nuclear magnetic resonance spectrum of polystyrene by means of model molecules
Authors: Jasse Bruno , Lauprêtre Françoise , Monnerie Lucien 
Published: April 2003

AbstractThe study of 2,4‐diphenylpentane (1), 2,4,6‐triphenylheptane (2) and 2,4,6,8‐tetraphenylnonane (3) by 13C NMR allows to compare the various chemical sequences of these compounds in terms of their chemical shifts.Methyl, methylene and aromatic C1 carbons are particularly sensitive to tacticity. Moreover, from the aromatic C1 chemical shifts it is possible to propose an assignment of the corresponding pentads of polystyrene.
Dipole moments of poly(oxytetramethylene) and poly(oxydecamethylene) chains
Authors: Riande Evaristo 
Published: April 2003

AbstractDielectric constants have been determined for poly(oxytetramethylene) and poly(oxydecamethylene) chains in the thermodynamically good solvent benzene. The data for the former polymer indicate that the dipole moment ratio 〈μ2〉/(Nm2), is independent of the chain length as has been predicted for chains of such structural features. The value of this ratio for α‐hydro‐ω‐hydroxypoly(oxydecamethylene) chains is in the same range as that obtained for poly(oxyethylene), poly(oxytetramethylene) and poly(oxyhexamethylene) and is in fair agreement with that predicted by the isomeric state theory.
Studies on polymerizations initiated by syncatalytic systems based on aluminium organic compounds, 7. Reaction mechanisms
Authors: Magagnini Pier Luigi , Cesca Sebastiano , Giusti Paolo , Priola Aldo , Maina Marcello Di 
Published: April 2003

AbstractThe polymerizations of isobutene and its copolymerizations with isoprene by syncatalytic systems consisting of an aluminium compound R2AlX (with R = alkyl and X = alkyl or halogen) and of a halogen or an interhalogen compound are initiated by the addition of a positive halogen ion to the monomer. Chlorine is the best co‐initiator. Whereas in this syncatalyzed polymerization of isobutene the initiation is relatively slow and monomer transfer and termination are unimportant, in the polymerization of isobutene by AlCl3 or EtAlCl2 the initiation is very fast and there is at least one efficient termination. Our interpretation of these results includes a discussion of the different initiations and chain‐breaking reactions.In the syncatalyzed polymerizations the initiation rate is governed by the relatively slow interaction of initiator and co‐initiator. Since the termination reactions are relatively unimportant, second and subsequent portions of monomer polymerize completely and faster than the first. The polymerizations initiated by AlCl3 or EtAlCl2 stop at incomplete conversion because of a termination which is chlorination of the carbenium ions by the anions; the AlCl3 thus formed is complexed by the unreacted monomer.
Phase changes of polyion complex between poly(methacrylic acid) and a polycation carrying charges in the chain backbone
Authors: Abe Koji , Ohno Hiroyuki , Tsuchida Eishun 
Published: April 2003

AbstractThe polyion complexes were obtained by mixing the aqueous solution of poly(methacrylic acid) and that of poly[(N,N,N′,N′‐tetramethyl‐N‐p‐xylylene)ethylenediammonium dichloride] (1). The forms of the polyion complex were observed as a homogeneous solution, a coacervate, or a precipitate under changing such conditions as the polyion concentration, pH, and the ionic strength. Especially, pH and the ionic strength affected the forms of the complex through the degree of dissociation of poly(methacrylic acid). The relations between these factors and the forms of the complex are shown as phase‐diagrams. The correlation among these factors is discussed, too.
Relation entre la solvatation préférentielle et la densité en segments de polymères de structure différente
Authors: Dondos Anastasios 
Published: April 2003

AbstractThis paper presents results on preferential solvation and viscosity in three ternary systems, (polystyrene (PS)‐benzene‐methanol, poly(2‐vinylpyridine)‐ethanol‐cyclohexane, and PS‐cyclohexane‐ethanol) using linear and branched polymers. It is shown that the representation ΔΛ′ (variation of the preferential solvation coefficient) as a function of ΔQ (variation of the segment density), gives curves which are not sensitive to branching and, therefore, caracteristic of the nature of the polymer and not of its structure. When there is an inversion in preferential solvation one can define “isosbestic” points, i.e. compositions of the solvent mixture for which Λ′ or ΔQ are independent of the molecular weight of the polymer.
The mean activity coefficient of cadmium polystyrenesulfonate
Authors: Vesnaver Gorazd , Špan Jože , Dolar Davorin 
Published: April 2003

AbstractThe electromotive force of the concentration cell with transference consisting of two identical cadmium amalgam electrodes and two solutions of cadmium polystyrenesulfonate with different concentrations, was measured for concentrations from 0,002 to 0,1 molal in monomer units. In the same concentration range transference and conductance measurements were performed in order to obtain the polyion transference number and the fraction of free counterions as functions of concentration. The logarithm of the mean activity coefficient derived from electromotive force and transference number is found to be a linear function of the logarithm of concentration. The experimental results are compared with the predictions of the cylindrical cell model and infinite line charge model. Satisfactory agreement between theory and experiment indicates that these models better represent the experimental results than the cube‐root relation which would follow from the ionic lattic structure of solution.
Synthesis and properties of co‐isotactic copolymers of functional vinyl aromatic monomers with chiral α‐olefins
Authors: Chiellini Emo , Carlini Carlo 
Published: April 2003

AbstractOptically active co‐isotactic copolymers of α‐olefins, like (R)‐3,7‐dimethyl‐1‐octene (1) or (S)‐4‐methyl‐1‐hexene (2), with functional para‐substituted styrenes were obtained by both copolymerization in the presence of Ziegler‐Natta catalysts and by chemical modification of the copolymers of styrene (5) with 1 or 2. By the first mentioned route copolymers of 4‐iodostyrene (3) and propyl 4‐vinylbenzenesulfonate (4) were prepared in satisfying yields. Fractionation by solvent extraction as well as the physical properties of the polymeric products, guarantee for the formation of co‐isotactic copolymer macromolecules. By the other route co‐isotactic copolymers of 1 or 2 with several para‐substituted styrenes (like 4‐halo, 4‐chloromethyl, 4‐diphenylphosphino, 4‐diphenylphosphinomethyl, and 4‐alkylammoniomethyl chloride derivatives) were prepared under conditions which do not give appreciable racemization of the chiral centers present in the main chain as well as in the lateral chain of the starting copolymers of styrene with α‐olefins. The reported data provide a useful way to attain stereoregular and chiral macromolecular materials, bearing either electron donor or chemically active functional groups, inserted in a highly homogeneous conformational environment.