bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymérisation anionique du styrène et du divinylbenzène en présence d'une charge polymère. Influence de la masse moléculaire du polystyrène précurseur et de la nature de la charge sur la formation du gel
Authors: Widmaier Jean‐Michel 
Published: April 2003

AbstractPolystyrene networks, blended with various polystyrene‐polyisoprene triblock copolymers, were prepared by anionic block copolymerization of styrene and divinylbenzene, the molar masses between crosslinks ranging from 5000 to 60000 g/mol. The influence of the linear polymer upon the formation of the host network was investigated by solvent extraction analysis and swelling experiments. It was found that removal of the soluble polymer out of the gel is completed within ten days of continuous extraction. The initial rate of desorption increases with decreasing the meshes of the network and with increasing the diene content of the block copolymer, i.e. the degree of incompatibility between the polymeric filler and the network. The equilibrium swelling degree of the remaining gels, completely freed of linear chains, was compared to the one of homologous model networks and revealed that the tri‐dimensional structure formed in the presence of a polymer has more defects than the one prepared in pure solvent.
Anionic polymerization of isopropenyl methyl ketone, 2. Microstructure and molar mass distribution of poly(isopropenyl methyl ketone)
Authors: Dotcheva Dobrinka T. , Tsvetanov Christo B. 
Published: April 2003

AbstractThe anionic polymerization of isopropenyl methyl ketone (IMK), initiated by alkali (Li+ Na+, K+, Cs+) derivatives of acetone, was studied in the temperature interval between −70 and 0°C. It was found that molar masses, molar mass distribution and microstructure of poly(isopropenyl methyl ketone) (PIMK) slightly depend on the polymerization conditions, counterion, temperature and solvent. The main side reaction appears to be a proton transfer due to the nature of the monomer. The polymer chain is built up mainly of 1,2‐ and cyclic monomeric units. Cyclization is favoured for cases in which the active centres interact with the adjacent monomeric units (small cation radius and low temperature).
Release of sodium salicylate from vinyl alcohol/n‐alkyl vinyl carbonate copolymers
Authors: Sánchez‐Chaves Manuel , Arranz Félix 
Published: April 2003

AbstractThis study is concerned with the sodium salicylate release from thin discs of vinyl alcohol/n‐alkyl vinyl carbonate copolymers into an aqueous medium under sink conditions. The drug content of the disc decreases with pseudo‐first order rate initially, whereas the drug quantity released is proportional to the square root of time. Data analysis supported the latter treatment, which is in agreement with the diffusional matrix model and invalidates the pseudo‐first order assumption. The diffusion coefficient D of vinyl alcohol/ethyl vinyl carbonate copolymers decreases with increasing ethyl vinyl carbonate content whilst D increases as both sodium salicylate concentration and temperature increase. The activation energy of diffusion was found to be 46,03 kJ/mol (11,00 kcal/mol).
Preferential adsorption behaviour of poly(alkyl methacrylate)s in 1,4‐dioxane/methanol
Authors: Katime Issa A. , Gargallo Ligia , Radić Deodato , Horta Arturo 
Published: April 2003

AbstractThe preferential adsorption of dilute solutions of poly(methyl methacrylate) and some poly(alkyl methacrylate)s in 1,4‐dioxane/methanol, at 298 K, was studied by laser light scattering. It was found that the inversion composition depends on the molar volume or the number of carbon atoms of the polymer side group. This result can be explained in terms of specific interactions between the carbonyl group of the esters and methanol.
Equilibrium copolymerization, 2. Effect of ultimate unit
Authors: Yan De‐yue , Cai Gang‐feng 
Published: April 2003

AbstractIn this paper, three cases of equilibrium copolymerization with the effect of ultimate unit are studied. The two‐dimensional molecular size distribution functions and other molecular parameters of the copolymer generated are derived. Then, with the aid of this theory, the values of all molecular parameters of the copolymer can be calculated from the comonomer feed composition and equilibrium constants of initiation and propagation.
Free‐radical initiating systems comprising organoaluminium compounds and organic electron‐acceptors
Authors: Florjańczyk Zbigniew , Lusztyk Ewa , Korenik Joanna 
Published: April 2003

AbstractThe systems comprising organoaluminium compounds, RAIX2 (R – CH3, C2H5, i‐C4H9, X – R or CI), and strong organic electron acceptors like quinones, tetracyanoolefins and nitro compounds were tested as redox type initiators of methyl methacrylate, acrylonitrile and styrene homopolymerization. The initiating radicals are produced via a single electron transfer from organoaluminium compounds to the acceptor molecules, followed by homolytical cleavage of the aluminium‐carbon bond. In the systems studied also stable radicals derived from the acceptor molecule like salts of semiquinones or anion‐radicals of tetracyanoolefins are formed beside alkyl radicals. The structure of some paramagnetic products formed in the reactions between the nitro compounds and triethylaluminium was established by means of ESR. The activity of initiators is discussed in terms of the mechanisms of radical and polar reactions taking place in the systems studied and in terms of interactions between radicals and radical‐scavengers produced.
Moisture‐curable rubber, 2. Moisture‐cure of brominated butyl rubber and silica composites
Authors: Yamashita Shinzo , Yamada Akira , Ohata Masatoshi , Kohjiya Shinzo 
Published: April 2003

AbstractSilica was compounded into the moisture‐curable rubber system of brominated butyl rubber (BIIR)/3‐aminopropyltriethoxysilane (APS). The compound was hot pressed and then cured in water at 70°C. The increment of network‐chain density (vs) by moisture‐curing became smaller in the presence of silica due to pre‐vulcanization during the hot pressing. The loading of silica did not simply increase the modulus of the moisture‐cured compound, since silica reacted with APS and reduced vs. An addition of tetraethoxysilane to the system was found to be effective to restore the reduced vs.
Etude de la simulation des réactions de polycondensation par la méthode de Monte‐Carlo
Authors: Chaumont Philippe , Gnanou Yves , Hild Gérard , Rempp Paul 
Published: April 2003

AbstractSimulation of polycondensation reactions using a Monte‐Carlo type method is discussed in detail. The process applies to reactions carried out in homogeneous isotropic phase and it is valid regardless of the number of constituents involved, and whatever the reactivity of the individual functions may be. However, it does not include cyclization, and cannot take into account the variation of the reactivity of a given function with conversion. The conditions that should be satisfied are discussed thoroughly; in particular, duplication procedures are introduced at various stages of the reaction to prevent the system from becoming too small at high conversion. The method was tested on two rather simple cases: the self condensation of AB‐type monomer molecules, and chain extension involving AA‐type macromolecules and BB‐type micromolecular coupling agents. The agreement between the simulation and the data of the classical polycondensation theory is very satisfactory.
Polybutadiène hydroxytéléchélique, 8. Etude de quelques relations microstructure‐propriétés des polyuréthannes obtenus par polycondensation en masse entre le polybutadiène hydroxytéléchélique anionique et le méthylène‐4,4′ diisocyanate de phényle avec ou sans allongeur de chaîne butanediol‐1,4
Authors: Ghafari Mahmoud El , Pham Quang‐Tho , Camberlin Yves 
Published: April 2003

AbstractPolyurethanes (PU), obtained with an anionic hydroxytelechelic polybutadiene (G1000), 4,4′‐methylenedi(phenyl isocyanate) (MDI) and 1,4‐butanediol (Bu), were investigated. Quantitative determinations of the compositions of the insoluble PU samples swollen in solvents were successfully achieved using high resolution 13C NMR. It was shown that without chain‐extender Bu, the glass transition temperature of PU increases linearly with increasing MDI mole ratios, and the moulded (G1000 + MDI) sheet obtained with a mole ratio NCO/OH – 1,1 behaves like a plasto‐viscoelastic material. With chain extender Bu, if the polycondensation is achieved in a mould, the composition of the sheet was found to be heterogeneous. The moulded (G1000 + MDI + Bu) sheet has a smaller elongation because of a higher modulus.
Dégradation controlée des polyisoprènes‐1,4 par le couple phénylhydrazine/oxygène, 2. Molécules modèles de structures phénylhydrazone non‐conjuguées d'extrémités de chaîne
Authors: Filho Eurico de Barros Lobo , Reyx Danièle , Campistron Irène , Casals Pierre‐François 
Published: April 2003

AbstractWith regard to the postulated intervention of phenylhydrazone structures during the degradation of 1,4‐polyisoprenes by the phenylhydrazine (1)/oxygen system, UV, 1H NMR, 13C NMR and mass spectroscopy as well as steric exclusion chromatography were applied for the characterization of model phenylhydrazones deriving from non conjugated carbonyl derivatives. Comparison of the results with some possible coexistent structural parameters gave some indications on the validity of these analytical tools for the identification of phenylhydrazone structures in oxidized polyisoprene.
Photoinitiators and photoinitiation, 6. The photodecomposition of α‐methoxydeoxybenzoin in a model substrate for acrylates
Authors: Hageman Hendrik J. , Oosterhoff Pieter , Overeem Ton , Polman Romkina J. , van der Werf Sake 
Published: April 2003

AbstractThe photodecomposition of α‐methoxydeoxybenzoin (1) was studied in the presence of methyl 2‐methoxyacrylate (9) as a potential model substrate for acrylic esters. Unexpectedly, 9 was found to undergo propagation reactions even at a relatively high 1/9 ratio (1:2), which led to an inconveniently large number of products. For this reason 9 is considered to be unsuitable as a model substrate for acrylic esters.
Poly(crown ether)s with rubidium cation selectivity
Authors: Shirai Masamitsu , Ueda Akihiko , Tanaka Makoto 
Published: April 2003

AbstractPolymers having both crown ether moieties as cation binding sites and cinnamoyl moieties as photodimerizable pendant groups were prepared by cationic polymerization of 2‐vinyloxyethyl 3‐(2,3‐benzo‐1,4,7,10,13‐pentaoxacyclopentadecen‐4′‐yl)acrylate (1) or 2‐vinyloxyethyl 3‐(2,3‐benzo‐1,4,7,10,13,16‐hexaoxacyclooctadecen‐4′‐yl)acrylate (2). The copolymer 3a was also prepared from 1 and 2. On irradiation with UV light, the cinnamoyl moieties of the polymers undergo dimerization in solution. The cation binding properties were investigated by using a fluorescent probe, 8‐anilino‐1‐naphthalenesulfonate. The cation binding ability of the photoreacted polymers was found to be higher than that of the original polymers. A significant template effect of alkali metal chlorides during photodimerization reaction on the cation binding ability was observed. The copolymers 4a, prepared by irradiation with template cations, show a remarkable rubidium cation selectivity, which is not observed for polymers with only 15‐crown‐5 or 18‐crown‐6 moieties.
Stereochemical aspects on the secondary insertion of propene monomer into a vanadium‐polymer bond
Authors: Doi Yoshiharu , Nozawa Fumie , Soga Kazuo 
Published: April 2003

AbstractThe stereochemistry of syndiotactic‐specific polymerization of propene with some soluble vanadium‐based catalysts was investigated by 1H NMR analysis of iodine‐bonded polypropylenes. The results of the 1H NMR analysis of chain‐end groups confirm that the majority of active centers exists as secondary vanadium‐carbon bonds during the chain propagation. The syndiotactic regularity of secondary‐inserted propylene units is not influenced by the sequence length of a growing polymer chain, but dependent upon the kind of aluminium component used as co‐catalyst.
Bestimmung von sekundären aminogruppen als fehlstrukturen‐in polyamid‐6.6
Authors: Horbach A. , Alewelt W. , Müller H. 
Published: April 2003

AbstractA new method was developed for the determination of the content of secondary amino groups and thus of the corresponding trifunctional branching points in polyamides‐6.6 introduced by thermal treatment. Bis(6‐aminohexyl)amine is formed by total acid hydrolysis of the polyamide and determined by reversed‐phase high‐performance liquid chromatography using off‐line pre‐column derivatization with 4′‐dimethylaminoazobenzene‐4‐sulfonyl chloride. In comparison to former analytical procedures described in literature, using paper chromatography, the new HPLC method has the advantage of higher sensitivity and better reproducibility.
An infrared spectroscopic investigation of the phase behavior of a polydiacetylene. The case of polydiacetylene with side groups containing a urethane function
Authors: Chang Chih , Hsu Shaw Ling 
Published: April 2003

AbstractThe infrared spectrum of polydiacetylene with side chains containing urethane functions (1) was analyzed. Based on the polarization data and the changes observed as a function of temperature, the multiple bands in the Amide I region observed for the film sample were attributed to the transition dipole coupling mechanism. The consequences of this new assignment illustrate the difficulty in using vibrational spectroscopy as a definitive tool to characterize the relationship between structural reorganization of the side chain and the chromic transition at high temperature.
The laser flash‐initiated polymerization as a tool of evaluating (individual) kinetic constants of free radical polymerization, 1. Outline of method and first results
Authors: Olaj Oskar Friedrich , Bitai Irene , Gleixner Günther 
Published: April 2003

AbstractA method is presented which allows the determination of kp/kt‐values in free radical polymerization. It is based on measurements of the (average) rate of polymerization under pseudostationary conditions, the polymerization being initiated by laser flashes of short duration. For ρkt t0 ≫ 1 (ρ being the additional polymer radical concentration produced by each laser flash, kt the bimolecular termination constant between polymer radicals, kp the rate constant of chain propagation, t0 the time separating two successive laser flashes) kp/kt may be obtained as the slope of a linear plot of the fractional conversion per flash vs. ln t0. Dividing the intercept by the slope yields ln (pkt). Thus, if p is accessible, separation of kp/kt‐data into its individual constituents may be accomplished without making any use of stationary polymerization data. Application of this method to the polymerization of styrene sensitized by benzoin or AIBN at 25°C gives kp/kt‐values of 1,0 · 10−6 which are in fair agreement with those obtained by other methods.
Dilute solution properties of imogolite
Authors: Donkai Nobuo , Inagaki Hiroshi , Kajiwara Kanji , Urakawa Hiroshi , Schmidt Manfred 
Published: April 2003

AbstractImogolite, a natural product in the clay fraction of Japanese soil, was characterized through its dilute solution properties. Various methods were employed for this characterization, including viscosity, sedimentation, static/dynamic light scattering, and small angle X‐ray scattering. All these measurements have revealed consistently that imogolite is represented by a rigid thin rod within the accuracy of available theories, where its repeat unit is composed of twelve gibbsite units. Since the evaluation of the chain length from the observed quantities depends on the molecular weight distribution, its effect was also considered where Mw/Mn ≈ 1,2 was estimated from the sedimentation profile.
Nonlinear optical self diffraction in a mesogenic side chain polymer
Authors: Eich Manfred , Wendorff Joachim H. , Ringsdorf Helmut , Schmidt Hans W. 
Published: April 2003

AbstractNonlinear optical self diffraction effects for a light beam in a liquid crystalline polymer in its isotropic fluid state was observed. This effect is characterized by the absence of a threshold intensity, a diffraction pattern that does not depend on the polarization of the reading beam relative to that of the writing beam and which cannot be disturbed by transversally applied static electrical fields. This effect is attributed to a thermally induced spatial refractive index modulation. The time constants of the response are of the order of ms.
Copolymerization via zwitterion, 5. β‐butyrolactone and 2‐methyl‐2‐oxazoline
Authors: Rivas Bernabé L. , Canessa Guido S. , Pooley Sonia A. 
Published: April 2003

AbstractThe zwitterionic copolymerization of 2‐methyl‐2‐oxazoline (MOX) as nucleophilic monomer with β‐butyrolactone (BUL) as electrophilic monomer was investigated in bulk and in solution (CH3CN) at 45°C. The copolymer composition was around 1,5/1,0 (BUL/MOX) as was established by 1H NMR. 1H and 13C NMR spectroscopy were used to identify the copolymers. The IR spectroscopy supported the NMR results. On the other hand, the copolymers behave as polyelectrolytes, according to viscosity determinations. A copolymerization mechanism through a zwitterion species is suggested.
Synthesis and characterization of inulin monosuccinates
Authors: Vermeersch Joan , Schacht Etienne 
Published: April 2003

AbstractInulin was succinoylated by reaction with succinic anhydride. The rate of esterification was markedly enhanced by addition of catalysts and increased in the following order, no catalyst < pyridine < 1‐methylimidazole < 4‐dimethylaminopyridine. NMR analysis of inulin monosuccinates of varying degree of esterification indicated that the hydroxyl groups in C‐6 and C‐3 position are more easily esterified than the C‐4 hydroxyl function.
Synthesis of linear poly(4‐vinylbenzaldehyde) by means of anionic living polymerization of 1,3‐dimethyl‐2‐(4‐vinylphenyl)imidazolidine and subsequent hydrolysis
Authors: Hirao Akira , Ishino Yoshiaki , Nakahama Seiichi 
Published: April 2003

AbstractPoly(4‐vinylbenzaldehyde)s (4) of known chain lengths and of narrow molecular weight distributions (M̄w/M̄n ≈ 1,1) were synthesized by means of anionic living polymerization of 1,3‐dimethyl‐2‐(4‐vinylphenyl)imidazolidine (1) with oligo[α‐methylstyryl]potassium (2) and subsequent acid hydrolysis to remove the imidazolidine protective group. The living polymer of 1 can initiate further polymerization of α‐methylstyrene, resulting in the preparation of a triblock copolymer of the type poly[α‐methylstyrene‐b‐(4‐vinylbenzaldehyde)‐b‐α‐methylstyrene] in quantitative yield after hydrolysis.
Generation of free radicals in poly(N‐vinylcarbazole) by thermal decomposition of peroxides
Authors: Hlouškova Zuzana , Szöcs František 
Published: April 2003

AbstractRadicals of poly(N‐vinylcarbazole) (PNVC), generated by thermal decomposition of peroxides, were studied by ESR. Apart from the known cation radical on nitrogen, formed in the process of ion‐radical decomposition of dibenzoyl peroxide, a carbon radical is observed on the main chain. The radical is formed by homolytic decomposition of dicumyl peroxide and is observed only when the system is subjected to high pressure. The mechanism of peroxide decomposition and of formation of PNVC radicals is discussed.
Studies on carboxymethylcellulose: Conductivity measurements of solutions, 2
Authors: Trivedi Harikrishna C. , Patel Raman D. 
Published: April 2003

AbstractThe conductivity behaviour of carboxymethylcellulose (CMC) solutions was studied using different types of neutralizing reagents (LiOH, NaOH, KOH); the following order of conductance of CMC solutions was observed: Li+ < Na+ < K+. This conductance behaviour of CMC solutions with respect to the size of counterions is explained qualitatively as well as quantitatively. Binding of Li+, Na+ and K+ ions onto the polymer molecule and the influence of the degree of substitution, ,DS, on the conductivity of CMC were also investigated. The conductivity of CMC solutions as well as the fraction of bound counterions increase with increasing DS, at a given degree of neutralization (α) for each type of counterion. The effect of DS on the polymer charge fraction, i/s, is in line with the counterion condensation phenomena of Oosawa. The results regarding the dependence of the equivalent conductance of the polyion, Δp, on DS are compared with literature data.
Enzyme‐synthetic polyampholyte systems
Authors: Dupommier Alain , Merle‐Aubry Liliane , Merle Yves , Sélégny Eric 
Published: April 2003

AbstractPolyampholytes, prepared by copolymerization of 2‐(N,N‐dimethylamino)ethyl methacrylate and methacrylic acid, increase the urease activity over a large pH range, when the acid content is between 24 and 68 mol‐%, while the activity of the enzyme is inhibited by polyampholytes having more than 84 mol‐% of methacrylic acid groups. The enzyme reaction induces conformational changes of the polyampholyte chain resulting from a pH increase due to the formation of ammonium carbonate. The contraction of the macromolecule was followed by viscometry and by the volume change of a cross‐linked analogous polyampholyte gel.
Struktur und eigenschaften der copolymere aus 1,3,5‐trioxan und 1‐chlor‐2,3‐epoxypropan, 1. Festkörpereigenschaften der copolymerkristalle
Authors: Michnev Bontcho , Mateva Rosa 
Published: April 2003

AbstractChanges in melting temperature, melting enthalpy and volume of the elementary cell of 1,3,5‐trioxane/1‐chloro‐2,3‐epoxypropane copolymers were investigated as function of the concentration of the comonomeric units involved.
Struktur und eigenschaften der copolymere aus 1,3,5‐trioxan und 1‐chlor‐2,3‐epoxypropan, 2. Morphologie der copolymerkristalle
Authors: Michnev Bontcho , Mateva Rosa 
Published: April 2003

AbstractThe morphology of copolymers from 1,3,5‐trioxane and 1‐chloro‐2,3‐epoxypropane was studied as function of polymerization time and amount of 1‐chloro‐2,3‐epoxypropane. Considerable changes of the morphology were observed when trespassing certain mole fractions of 1‐chloro‐2,3‐epoxypropane monomeric units in the copolymer chain.
Two‐Phase(water/organic) free radical polymerization of water‐soluble vinyl monomers using lipophilic acylated β‐cyclodextrins as initiator carrier
Authors: Ryoshi Hiroto , Kunieda Norio , Kinoshita Masayoshi 
Published: April 2003

AbstractThe acylated β‐cyclodextrins, heptakis(2,3,6‐tri‐O‐acetyl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐obutyryl)‐β‐cyclodextrin, heptakis(2,3,6‐tri‐O‐butyryl)‐β‐cyclodextrin, and heptakis(2,3,6‐tri‐O‐pivaloyl)‐β‐cyclodextrin, cause a marked increase in the rate of polymerization of water‐ soluble vinyl monomers using water insoluble initiators in the two‐phase system consisting of water and an organic solvent (chloroform/ligroin, volume ratio 1 : 4). A plausible mechanism for this polymerization is proposed: The lipophilic acylated cyclodextrin acts as an initiator carrrier from the organic to the aqueous phase where polymerization takes place.
Study on the modification of soluble poly(epichlorohydrin) with 2‐mercaptoethanol and thioglycolic acid
Authors: Lamot Ryszard 
Published: April 2003

AbstractFrom 1‐chloro‐2,3‐epoxypropane (epichlorohydrin), soluble poly(epichlorohydrin)s were prepared with molar masses in the range of 3,7 · 104 to 1,7 · 105 g/mol, using a complex of epichlorohydrin with hexaamminecalcium. These poly(epichlorohydrin)s were modified by reaction with 2‐mercaptoethanol or thioglycolic acid. The yields of these reactions range between 40 and 60%. The drop of molecular weight due to modification oscillate between 3,8 and 48,1%. The structure of the modified polymers was confirmed by elemental analyses, thermogravimetric and mass spectroscopic investigations. These chemical modifications carried out with poly(epichlorohydrin)s lead to water‐soluble products.