bluuebunny/crossref_metadata_2025_split huggingface dataset:
Terpolymérisation acrylonitrile/styrène/acrylate de méthyle, 3. Etude du mécanisme de la copolymérisation en emulsion
Authors: Guillot Jean , Guerrero Leonardo Rios 
Published: April 2003

AbstractEmulsion copolymerization appears to be very suitable for mechanistic investigations in emulsion polymerization. A study of the emulsion copolymerization under various conditions (batch, semi‐continuous, composition controlled reactor) of the styrene (S)/acrylonitrile (A) system is presented, which may have model character due to the very different monomer solubilities both in water and in their polymers. Comparison of copolymer composition with monomer mixture composition in the various phases (determine by gas chromatography analysis after the emulsion has been centrifuged) confirms that the monomer/polymer particles are the main loci of polymerization. The monomier / water ratio and the amount of emulsifier sodium dodecylsulfate influence the polymerization rate (Rp) as well as the particle size (D̄p). The existance of a monomer droplet phase seems also to be determinant for many features of such as a copolymerization as, e. g., the evolution of Rp, D̄p, number of particles (Np) etc. In addition, in a batch process, the composition drift versus conversion modified the monomer solubilities within the particles, the emulsifier adsorption, the particle growth which appeared to reach a limiting size, mainly due to electrostatic hindrance. It is also observed, Whatever may be the emulsion polymerization process, that Rp is not proportional towards Np, but towards dNp/dt; this might be related to the particle growth rate. A. mechanism is derived, based on experimental data and thermodynamic considerations, which allows to take into account molecular interactions (χ), coplymer composition, Dp, interfacial tension (γ), and above all, the actual monomer feed composition within the polymerization loci, as the copolymerization proceeds.
Spacer effect in the template polycondensation of nucleotide analogs with diamines
Authors: Nakagawa Hiroshi , Muraki Michiro , Miura Yozo , Kinoshita Masayoshi 
Published: April 2003

AbstractThe template effect of polymers containing the adenine residue, 6, bound to a polystyrene backbone via a spacer group, on the polycondensation of active esters of thymine, 1, and theophylline, 2, with piperazine was studied in pyridine/methylene chloride or DMF. Template polymers accelerated the polycondensation of 1 with diamines by a factor of 5–20, but the polycondensation of 2 with piperazine showed no considerable template effect.
Synthèse de compoisés photoréticulables, 4. Estérification de l'acide acrylique sur les télomères de l'acrylate d'hydroxy‐2 éthyle
Authors: Boutevin Bernard , Maliszewicz Marc , Piétrasanta Yves 
Published: April 2003

AbstractSeveral telomers were prepared by redox catalysis from 2‐hydroxyethyl acrylate (1) and telogens such as carbon tetrachloride, methyl trichloroacetate, 1, 1, 1‐trichlorotrifluoroethane, and 2,4,4,4‐tetrachloro‐2‐methylbutyric acid (2d), as well as block‐cotelomers from 1 and a telomer 4 prepared from chlorotrifluoroethylene and carbon tetrachloride. Polyols (3a–d and 5) with two to twenty primary hydroxyl groups were obtained. They were esterified with acrylic acid, to obtain new photosensitive compositions. (6a–d).
Zur alterung von wäßrigen polyacrylamid‐lösungen
Authors: Mächtle Walter 
Published: April 2003

AbstractFor 62 days the aging behaviour of diluted solutions of an extremely pure, linear, noncharged polyacrylamide with Mw = 8400 000 g/mol in water was examined. The solutions were stored in a sterile surrounding at 298 K. The following quantities, all of which give information about the molecular weight or the dimension of the macromolecules, were measured: the intrinsic viscosity [η], the sedimentation cofficient s0, the translational diffusion coefficient (Dt)z, the molecular weight, Mw, and the radius of gyration, Rz. Within the accuracy of the measurements all these quantities remained constant. That means, in contrast to other authors, that we could not observe any aging effect in our solutions. It seems that polyacrylamide dissolved in water shows a behavior like a coil molecule in a thermodynamically good solution.
Some solution properties of poly(ethyl methacrylate)
Authors: Olayemi Julius Y. 
Published: April 2003

AbstractThe viscosity of dilute solutions of poly(ethyl methacrylate) in each of methyl acetate, ethyl acetate and isobutyl acetate was studied over the temperature range of 20–65°C. The intrinsic viscosity either remained approximately constant or slightly decreased over the temperature range because of conformational changes. The temperature ranges of conformational change were 40–50°C, 40–50°C, and 35–55°C for the polymer in methyl acetate, ethyl acetate, and isobutyl acetate, respectively. The Huggins constant was also influenced by the type of solvent and by temperature changes, especially over the temperature range in which conformational changes took place. Conformational changes of poly(ethyl methacrylate) in aliphatic organic esters as solvents are believed to be due to changes in the interaction between the polymer segments and the solvent.
Anomalous diffusion of dextran in DMF‐water mixed solvent system: A case of preferential solvation of the dextran molecule?
Authors: Amu Thomas C. 
Published: April 2003

AbstractAnomalous diffusional behaviour — not evident for the carbohydrate oligomers glucose, sucrose, and raffinose — was observed for dextran in the DMF‐H2O mixed solvent system at 25°C. The plot of interdiffusion coefficients (D0) for the dextran against the mole fraction of water (X) in the DMF‐H2O mixtures shows a discontinuity with a maximum in D0 at X = 0,85. Plots of intrinsic viscosities [η], for two higher molecular weight dextrans, against X also show transitions at X = 0,85. The anomalous behaviour of the dextrans at this solvent composition is discussed in terms of a solvent induced conformational transition of the dextran molecule.
Biozide polymere, 6. Synthese und polymerisation von acryl‐ und methacrylsäurederivaten des 3‐amino‐1,2,4‐triazols
Authors: Bauer Hans‐Jürgen , Hartmann Manfred , Wermann Kurt 
Published: April 2003

AbstractPreparation and characterization (by IR and 1H NMR spectroscopy) of isomeric methacrylic acid and acrylic acid derivatives of the herbicide 3‐amino‐1,2,4‐traizole are described. Their radical polymerization and copolymerization with styrene or methyl methacrylate give polymers containing the herbicide moiety as pendant groups bound via acyl groups at the amino group or at the ring nitrogen. The reactivity ratios were determined for the isomeric methacrylic compounds.
Télomères monofonctionnels du chlorure de vinyle, 4. Synthèse et caractérisation par catalyse rédox
Authors: Boutevin Bernard , Piétrasanta Yves , Taha Mohamed 
Published: April 2003

AbstractMonofunctional telomers of vinyl chloride (1) were synthesized by two ways. In the first one, the telomers resulting from the reaction of 1 with carbon tetrachloride were used as telogenic agents to react with allyl acetate leading to a monoadduct. In the second one, monofunctional telogens were used in a redox catalyzed reaction with 1. Trichloroacetic acid and its esters (2b–d) were applied as telogens. The theoretical maximum yields and the number average degrees of polymerization at these yields were calculated and compared with the experimental results.
On the initiation sites of poly(vinyl chloride) dehydrochlorination, 1. Kinetic view of the problem
Authors: Valko L. , Šimon P. , Kellö V. 
Published: April 2003

AbstractThe kinetics of the thermal dehydrochlorination of PVC was investigated with respect to the initiation mechanism of the hydrogen chloride chain elimination. The constant rate of dehydrochlorination in the early stages of the dehydrochlorination process is explained by an intra‐chain initiation mechanism which is a consequence of a constant amount of active sites (structural irregularities) incorporated in the chains. After an initial period, dehydrochlorination is occurring in a random way, and (or) by an inter‐chain dehydrochlorination mechanism initiated by a “sudden polarization” effect between the postulated zwitterion and a meanwhile unreacted CH2CHCl group.
Thermodynamic and hydrodynamic properties of aliphatic polyesters, 1. Solubility, intrinsic viscosity, and molecular weight of poly(β‐propiolactone)
Authors: Rosenvasser Daniel , Casas Aurelio Sagrario , Figini Ruben V. 
Published: April 2003

AbstractAbsolute molecular weight, intrinsic viscosity, refractive index increment, refractive index, partial specific density, solubility and molecular weight distribution of poly(β‐propiolactone) is studied. The measured molecular weights range from 40000 up to nearly 1000000. The relationship between intrinsic viscosity and molecular weight [η] = 0,0259 · M ml/g (CHCl3, 30,0°C) shows that the polymer molecule is a linear flexible chain.
Étude calorimétrique des interactions polyéthylène/liquide, 1. Interface présentant un angle de contact
Authors: Blanc Raymond , Sage Daniel , Berticat Philippe 
Published: April 2003

AbstractA technique is described for the measurement of the heat of immersion for polyethylene with a 2 . 10−3 J accuracy. For the studied systems, the heat of mixing is positive and due to solubility of the liquid in the amorphous phase of the polymer. The dissolved fraction is estimated from the heat of mixing according to Flory's theory. Measurement of the surface energy from single crystals indicates that this surface constituted of the folds of the chains behaves as an amorphous phase. Last, the heat of immersion is compared to the value calculated from the contact angle. If the solubility of the liquid is very small, the agreement is good. The case of water is studied: the negative value of the heat of immersion ΔHi proceeds from a change in water structure and a decrease of the enthalpy due to the contact with apolar compounds. This value allows to estimate the solubility of water in polyethylene.
Preparation of 5‐hydroxy‐7‐methoxy‐2,2‐dimethyl‐6‐octyl(and 8‐octyl)‐4‐chromanones and their Properties as UV Absorbers
Authors: Ninagawa Akira , Iseki Takayuki , Matsuda Haruo 
Published: April 2003

Abstract5‐Hydroxy‐7‐methoxy‐2,2‐dimethyl‐6‐octyl(and 8‐octyl)‐4‐chromanones (2a and 2b) were synthesized via 5,7 dihydroxy‐2,2‐dimethyl‐6‐octyl (and 8‐octyl)‐4‐chromanones (1a and 1b) from phloroglucinol as a starting material. Cyclohexane solutions of 1a, 1b, 2a, and 2b were irradiated. The photostability of 2a and 2b was found to be better than that of 1a and 1b. Poly(vinyl chloride) film containing 6, 7 wt.‐% of 2b was found to be most stable against photooxidation.
The stochastic kinetics of intramolecular reactions in linear polymers
Authors: Raap Ignatius A. , Gröllmann Ulrich 
Published: April 2003

AbstractThis paper deals with the kinetics of reactions of linear flexible macromolecules in solution possessing initially several reactive sites per macromolecule. It is assumed that the reactive sites interact with each other encounter‐controlled and that both intra‐ and intermolecular reactions are possible. On the basis of the theory of stochastic kinetics in microsystems, equations were derived, describing the kinetics of intramolecular reactions as a function of the molecular weight distribution. An important application of this theoretical treatment pertains to the distribution between inter‐ and intramolecular reactions. A demonstration for typical reaction conditions reveals the influence of rate parameters and of the average number of reactive sites per macromolecule r̄(0) on the proportionate distribution expressed by fA = f (r̄(0)); (fA = fraction of intramolecular reactions). This function is only weakly influenced by varying the width parameter β in the case of Schulz‐Zimm molecular weight distributions from β = 1 to → ∞.
The chemically initiated high pressure polymerization of ethylene
Authors: Buback Michael , Lendle Hubert 
Published: April 2003

AbstractThe kinetics of the high‐pressure ethylene polymerization initiated by di‐tert‐butyl peroxide were measured via quantitative near‐infrared spectroscopy at temperatures between 130°C and 165°C to a maximum pressure of 3 kbar. The overall polymerization rate was found to be first order in ethylene concentration and of the order 0,5 in peroxide concentration. The overall activation energy and the overall activation volume were determined to be E0 = 107,2 ± 7,5 kJ · mol−1 and Δ V0≠ = − 17,5 ± 5,0 cm3 · mol−1, respectively. From the overall quantities and from the decomposition rate of di‐tert‐butyl peroxide determined in independent spectroscopic high‐pressure high‐temperature experiments, kp · kt−1/2 (kp and kt are the propagation and termination rate constants, respectively) and the corresponding activation parameters, Ep – 1/2 Et and Δ vp≠ − 1/2 Δvt≠, were derived for the high‐pressure ethylene polymerization. These data enable the overall polymerization rate to be determined also for high‐pressure ethylene polymerizations initiated in any different way, provided the initiation rate law is known. The procedure is illustrated for the ethylene polymerization initiated by tert‐butyl peroxypivalate.
Crystallization of polydisperse polyethylene fractionated according to pennings' method
Authors: Hert Marius , Rault Jacques , Robelin Elisabeth 
Published: April 2003

AbstractIt is shown that the molten state and the semi‐crystalline state of polydisperse polyethylene are interrelated. Large polydisperse fractions obtained according to Pennings' fractionation method were studied by small angle X‐ray scattering and differential thermal analysis; the long period, depending on the molecular weight distribution, is shown to be given by the weight average end‐to‐end distance of the coils; the long chains with molecular weights M > 105 behave as a series of “sub‐chains” with molecular weight M* = 105 which crystallize independently. The same result is found for fractions with narrow molecular weight distribution and for mixtures of polyethylene fractions.
Asymmetric induction in the copolymerization of (–)‐3‐(β‐styryloxy)menthane with styrene
Authors: Yamaguchi Hidemasa , Sekioka Ken‐ichi , Kurokawa Masahiro , Doiuchi Tohru 
Published: April 2003

AbstractAsymmetric induction in the copolymerization of (–)‐3‐(β‐styryloxy)menthane (1) with styrene was investigated. The copolymers obtained in the presence of BF3 · OEt2 are optically active. The absolute value of the specific rotation of the copolymers was found to be higher than that of the homopolymeric mixture, whatever the composition. After ether cleavage reaction of the copolymers, the products are still optically active. The result suggests that an asymmetric induction takes place in the polymer main chain.
Redox initiators for cationic polymerization: The diaryliodonium Salt/Sn(II) redox couple
Authors: Crivello J. V. , Lee J. L. 
Published: April 2003

AbstractDiaryliodonium salts undergo facile copper catalyzed reduction in the presence of Sn(II) compounds. Such redox couples can be employed for the in situ generation of active initiators for cationic vinyl and ring opening polymerizations. Two mechanisms are proposed for the reduction reaction to explain the stoichiometry of the reactants and nature of the products formed. The polymerizations of several representative cationically polymerizable monomers were studied.
Vinyl polymerization initiated with systems of dimethylaniline N‐oxide and some chlorosilanes
Authors: Sato Tsuneyuki , Yamada Kentaro , Yasuda Takeyasu , Otsu Takayuki 
Published: April 2003

AbstractBinary systems of dimethylaniline N‐oxide (DMAO) and some chlorosilanes were found to be effective initiators for vinyl polymerization. The initiating activity of the chlorosilanes decreases in the following order: SiCl4 > CH3SiCl3 > (CH3)SiCl2 > (CH3)3SiCl. The copolymerization of methyl methacrylate (MMA) with styrene, initiated with the system DMAO/SiCl4, propagates via a radical mechanism. The polymerization of MMA with the system DMAO/SiCl4 was investigated kinitically in acetonitrile. The overall activation energy of the polymerization was calculated to be 44,4 kJ/mol, an extremely low value. The initial poly‐merization rate(Rp) is of 1st order in monomer concentration. Rp is proportional to the square root of the DMAO concentration, and slightly dependent on the SiCl4 concentration for high SiCl4 concentrations. This suggests that a complex is formed between DMAO and SiCl4. Spec‐troscopic results on the system DMAO/SiCl4 also indicate the formation of a complex. A yellow crystalline compound was isolated from the reaction of DMAO with SiCl4 at room temperature in methylene chloride/diethyl ether (1:3, by vol.). The complex has a composition of four moles of DMAO and one mole of SiCl4. From these results and from spin trapping studies, a possible initiation mechanism is proposed for the polymerization initiated with the system DMAO/chlorosilane.
Polymerization of lactams, 55. Cyclic dimer of 6‐caprolactam and its polymerization
Authors: Krajník Václav , Kondelíková Jaroslava , Králíček Jaroslav , Karhan František 
Published: April 2003

AbstractPolymerization of the cyclic dimer of 6‐caprolactam was investigated in N‐methyl‐2‐pyrroli‐done solution at 260°C under initiation with 6‐aminocaproic acid or anhydrous phosphoric acid on the one hand, and in the solid phase at 230, 260, and 280°C in the absence of any other component or under initiation with anhydrous phosphoric acid, on the other. Monomeric 6‐caprolactam was formed in all cases already at the beginning of reaction. It has been suggested that, in addition to the direct incorporation of the cyclic dimer into a polymer chain, the dimer is alos incorporated via the monomer, which is formed from the dimer by an intermolecular transamidation reaction.
Influence of water in the polymerization of tetrahydrofuran
Authors: Alamo Rufina , Guzmán Julio , Fatou José G. 
Published: April 2003

AbstractThe polymerization of tetrahydrofuran by acetyl perchlorate as initiator in methylene dichloride solution in the presence of water shows the same rate‐constant and yields polymer of the same number average degree of polymerization as its polymerization in anhydrous systems provided that [H2O] < [CH3CO+ClO4−]. The fact that water causes neither retardation nor transfer is explained.
Etude par 13C NMR d'alcanes lourds mono‐ et diramifiés. Modèles de polyoléfines
Authors: Frêche Patrick , Grenier‐Loustalot Marie‐Florence , Metras Franck , Gascoin Alain 
Published: April 2003

Abstract13C NMR spectra were obtained for a series of branched, heavy alkanes at 37°C and 100°C, which provide a model set for describing the branched sequences in low density polyethylene (LDPE) and copolymers of α‐olefines. In addition, they provide a model set for revising the empirical Grant‐Paul and Lindeman‐Adams additive coefficients and corrective terms for pre‐dicting 13C chemical shifts of alkanes. The resulting revised parameters (for 37°C and 100°C) produce more accurate predictions of 13C NMR spectra for branched alkanes and it is noted that some corrective terms can be temperature‐sensitive.
Determination of poly(ethylene oxide) crystallinity by inverse gas chromatography
Authors: Fernández‐Berridi M. J. , Martín Guzmán G. M. , Iruin J. J. , Elorza J. M. 
Published: April 2003

AbstractSpecific retention volumes Vg for acetone, 1‐propanol, ethyl acetate, hexane, and tetrahydrofuran were obtained by inverse gas chromatography using poly(ethylene oxide) as stationary phase. Measurements were done at different flow rates, different injected sample amounts, and with three columns of different packing. Retention volumes were measured above and below the melting temperature of the polymer. The shape of the flow diagram and the variation of retention time tr with the sample amount depend on the temperature, flow rate, and the nature of the probe. Moreover, and due to the polymer polarity, the retention volume is a linear function of the column coating. All these factors must be controlled in order to obtain an accurate value of Vg which allows the determination of the crystallinity of the stationary phase. Above Tm, Vg is independent of flow, packing, and amount of the injected sample.
Polyvinylpyridine complexes of ruthenium(III) chloride
Authors: Clear James M. , Kelly John M. , Vos Johannes G. 
Published: April 2003

AbstractA series of polymeric materials were prepared by reacting poly(2021840311vinylpyridine) or poly‐(4‐vinylpyridine) with ruthenium (III) chloride in refluxing methanol. Mole ratio of RuCl3 to vinylpyridine (Ru: PVP ratio) was varied from 2:1 to 1:20. From IR and UV/VIS spectroscopic data it is shown that several kinds of ruthenium‐PVP complexes are present, their relative proportions depending on the Ru: PVP ratio of the original reaction mixture and on the reaction time. The spectroscopic properties of the polymer complexes are compared to those of methylpyridine complexes of ruthenium(III) chloride.
Polymeric schiff's base chelates and their precursors, 4. Syntheses of schiff's base chelates from diaminomaleonitrile and investigation of their activity for the valence isomerisation of quadricyclane to norbornadien
Authors: Wöhrle Dieter , Bohlen Heike , Rothkopf Hans‐Werner 
Published: April 2003

AbstractVarious low molecular and polymeric Schiff's base chelates 9 – 13, 15 – 19, and 22 were synthesized from Z‐2,3‐diamino‐2‐butene dinitrile (3), the corresponding o‐hydroxyaldehydes, and Co(II), Ni(II), or Cu(II) acetate. Their IR, UV, and MS data are discussed. The cobalt containing Schiff's base chelates including the polymeric ones, were found to be effective catalysts for the isomerization of quadricyclane (24) into norbornadiene (23). First results are reported.
Promotion of charge‐transfer complex formation by β‐ or γ‐cyclodextrin
Authors: Kobayashi Nagao , Saito Rumiko , Ueno Akihiko , Osa Tetsuo 
Published: April 2003

AbstractThe formation of charge‐transfer (CT) complexes between eleven naphthalene derivatives and eight di‐ or trinitrobenzene derivatives in water and in water‐organic solvent systems has been studied in the presence and absence of β‐ or γ‐cyclodextrin (β‐ or γ‐CDx), respectively. Data of UV absorption and circular dichroism (CD) clearly revealed that γ‐CDx, in several cases, assists CT complex formation by accommodating both electron donor (D) and acceptor (A) molecules in its cavity simultaneously. Thus the weak CT band was intensified and even some systems in which CT complex formation was usually not observed produced CT complexes by the addition of γ‐CDx. In contrast, β‐CDx did not promote markedly the CT complex formation except in one case. It did promote the CT complex formation between α‐naphthylacetic acid (α‐NAA) and picric acid (PA), manifesting the capability of β‐CDx to include two aromatic molecules. Magnetic circular dichroism (MCD) associated with the CT bands was detected for a π ‐ π* type CT complex for the first time, but its intensity was quite weak as anticipated from theory.
Kinetics of the nitrogen dioxide initiated polymerization of acrylic acid
Authors: Mishra Mahendra K. , Bhadani Suraj N. 
Published: April 2003

AbstractAcrylic acid (AA) was polymerized with NO2 in tetrahydrofuran (THF) and in 1,4‐dioxane. The effects of monomer and initiator concentration and of temperature on polymer conversion, initial rate of polymerization, and molecular weight were studied. The overall activation energy of polymerization was found to be 16,3 kcal mol−1 (68,23 kJ · mol−1) and 15,54 kcal · mol−1 (65,05 kJ · mol−1) in THF and in 1,4‐dioxane, respectively. High molecular weight polymers (M ca. 105) were obtained. The polymerization appears to be initiated by free radicals.