bluuebunny/crossref_metadata_2025_split huggingface dataset:
Étude de l'état solide des copolymères du chlorure de vinylidène avec le chlorure de vinyle, l'acrylonitrile et le méthacrylate de méthyle, 1. Structure des copolymères, modélisation mathématique en relation avec la structure chimique des chaînes
Authors: Douillard Alain , Dumont Bernard , Guillot Jean 
Published: April 2003

AbstractThe properties of a random copolymer are not only determined by composition, but also by the repartition of the monomeric units along the chain. In order to explain the properties of such a copolymer it is necessary to know the sequence distribution or microstructure, each sequence by itself showing structural characteristics: length, relative position, etc. It is thus necessary to conduct a precise synthesis process, and to know the kinetic parameters of the polymerization reaction. Knowledge of the kinetic invariants and monomer feed composition gives access to the theoretical sequence distribution. By different physicochemical methods (NMR, IR and UV spectroscopy), the results obtained by calculation are confirmed. Specifically the effect of microstructure and composition on the properties of some vinylidene chloride (VDC) copolymers with acrylonitrile (AN), vinyl chloride (VC) and methyl methacrylate (MMA) is studied. VDC leads to a very cristalline polymer, whereas PVC generally shows very poor cristallinity, and PAN shows particular structural characteristics. VDC copolymers can easily crystallize when they are rich in VDC. Generally the polymers are semi‐crystalline with an amorphous phase. A theoretical model accounting for the lamellar structure and crystallinity of VDC copolymers is described. It utilizes the microstructural data, obtained by a kinetic study and some simple hypotheses, among them the possibility for molecules to slide along each other. This sliding brings together the material which is crystallizable in determined areas. It is thus possible to explain the presence of crystallinity peaks, or at least of paracrystallinity, up to a relatively high amount of comonomer MMA, AN and especially VC in the diffractograms of VDC copolymers with MMA, AN and VC. The paracrystalline domains are defined as areas which can present some degree of order at great distance, with a relatively high amount of comonomer defects.
Polymers based on p‐aminophenol, 2. Poly(oxycarbonylimino‐1,4‐phenylene) and related polyurethanes
Authors: Kurita Keisuke , Matsuda Shoko , Iwakura Yoshio 
Published: April 2003

AbstractThe simplest AB‐type aromatic polyurethane, poly(oxycarbonylimino‐1,4‐phenylene) (1), was successfully synthesized by pyrolysis of phenyl N‐p‐hydroxyphenylcarbamate. The resulting polyurethane was colorless and soluble in some organic polar solvents. It was also confirmed to undergo “apparent sublimation” by first thermal dissociation to p‐hydroxyphenyl isocyanate and subsequent repolymerization to the polyurethane on a cool surface. Three other polyurethanes with related structures were prepared by solution addition polymerization to compare the unique properties. The most remarkable difference was observed in thermal behavior. The polyurethane 1 was found to dissociate much more readily at elevated temperatures than a similar AABB‐type polyurethane derived from hydroquinone and p‐phenylene diisocyanate.
Polymer retention mechanisms in GPC on active gels, 3. Poly(dimethylsiloxane) and poly(methyl methacrylate)
Authors: Figueruelo Juan E. , Soria Vicente , Campos Agustín 
Published: April 2003

AbstractElution curves on spherosil gels in pure and mixed eluents of poly(dimethylsiloxane), PDMS, and poly(methyl methacrylate), PMMA, as well as those of polystyrene, PS, just for comparison, have been determined. In a general way, PDMS elution volumers fit to those of PS, whereas PMMA elution curves shift to higher retention volumes. The differences in retention volumes between the different polymeric solutes have been interpreted in terms of differences in polymer‐gel and polymer‐solvent interactions. Hydrogen‐bonding seems to be the main contribution to solute‐substrate interactions.
Determination of the stereoisomers distribution in 1,4‐polybutadiene chains: A general restatement of the question
Authors: Walckiers Emmanuel , Julémont Michel 
Published: April 2003

AbstractAfter a definition of the bases of statistical computations allowing the description of the cis and trans stereoisomers distribution along the 1,4‐polybutadiene chains, the relationships between the distribution statistics and the mechanism of propagation are deduced. The parameters necessary and sufficient to describe the stereoisomer proportions and distribution are also established, as well as the parameters related to the determination of the most probable propagation mechanism. Analysis of typical samples are proposed to illustrate the method. Finally, a way is settled for computing the mean length of stereosequences.
Determination of rate constants of initiation and propagation in the cationic polymerization of α‐methylstyrene with CF3SO3H and H2SO4
Authors: Takarabe Kunihide , Kunitake Toyoki 
Published: April 2003

AbstractThe polymerization of α‐methylstyrene with CF3SO3H and H2SO4 as initiators was studied at 30°C in dichloroethane by the stopped‐flow/rapid‐scan spectroscopic technique. The propagating cation shows λmax at 336–340 nm. The initiation process and the early stage of propagation were analyzed kinetically on the basis of the cation formation and monomer consumption by taking into account the equilibrium monomer concentration. The rate of initiation with CF3SO3H was found to be proportional to the concentrations of CF3SO3H and monomer, but the initiation with H2SO4 is not proportional to the H2SO4 concentration. The rate constant of initiation was estimated to be (2 ± 1)·103 1.mol−1.s−1 with CF3SO3H, and similar values were found with H2SO4. The rate constant of propagation is 3.104 1.mol−1.s−1 with CF3SO3H as initiator and 106 − 107 1.mol−1.s−1 with H2SO4 as initiator. These kp values are close to that obtained previously in the radiation polymerization. Finally, λmax values of the propagating cation, obtained by the stopped‐flow technique, were collected.
Cosolvents of PMMA
Authors: Fernández‐Piérola Inés , Horta Arturo 
Published: April 2003

AbstractSeveral cosolvent mixtures for PMMA are reported. Their cosolvency has been confirmed by studying phase separation temperatures as a function of solvent composition. The results show that they are very powerful cosolvents. Acetonitrile forms such cosolvent mixtures with compounds containing different chemical groups (ester, ketone, alcohol, chloroalkane). The mixtures of acetonitrile with alcohols are nonsymmetrical with respect to the solubility parameter value of PMMA. They cannot be explained by simple δ theory. The mixture of formamide with ethanol is also nonsymmetrical and constitutes a true cosolvent pair for PMMA. The associating tendency of the polymer in the single solvent, plus the somewhat ordered structure of the pure liquids, are invoked to suggest that cosolvency is attained by breaking such order and association (in addition to the existence of unfavourable interactions between the cosolvents).
Living anionic stereospecific polymerization of 2‐vinylpyridine, 2. Kinetics of polymerization and nature of active centres
Authors: Soum Alain , Fontanille Michel 
Published: April 2003

AbstractThe kinetic study of the propagation reaction and the viscosity measurements on solutions of active centres indicate that the living stereospecific polymerization of 2‐vinylpyridine initiated by organomagnesium compounds in hydrocarbon solvents, proceeds through unsymmetrical non‐aggregated ion pairs. Cryoscopic measurements on a model compound of the active centres, indicate the lack of aggregation which is attributed to the complexation of the magnesium cation by the last and the penultimate pyridine ring of the living polymer chain.
Polymers containing enzymatically degradable bonds, 2. Poly[N‐(2‐hydroxypropyl)methacrylamide] chains connected by oligopeptide sequences cleavable by chymotrypsin
Authors: Rejmanová Pavla , Obereigner Blahoslav , Kopeček Jindřich 
Published: April 2003

AbstractCopolymers of N‐(2‐hydroxypropyl)methacrylamide (1) with p‐nitrophenyl esters of N‐methacryloylated oligopeptides (2–16) were prepared. These copolymers were crosslinked below the gel point by diamines (17–27). The crosslinks connecting poly[N‐(2‐hydroxypropyl)methacrylamide] chains contained an oligopeptidic sequence of 2–4 amino acids, cleavable by α‐chymotrypsin: ‐Gly‐X‐Y‐ (X… Gly, Ala, β‐Ala, Val, Leu, Ile, Phe, D‐Phe; Y… Phe, Tyr), ‐Gly‐Gly‐Phe‐Y‐; ‐U‐Gly‐Val‐Phe‐ (U… Ala, Gly); ‐Gly‐Phe‐W‐ (W… Ala, Gly, D‐Phe); ‐Gly‐Phe‐Ala‐U‐. The changes in the distribution of molecular weights of the studied copolymers, after incubation with α‐chymotrypsin, allowed us to estimate the amount of degradable crosslinks and to determine the relationship between the structure and cleavability. The results are interpreted from the viewpoint of the contribution of subsite (S‐P) interactions to the degradability of the studied polymers.
Polymeric drugs by direct copolymerization: Polymer of β‐adrenergic antagonist alprenolol and its binding to receptors and antibodies
Authors: Pitha Josef , Zjawiony Jordan , Lefkowitz Robert J. , Caron Marc G. 
Published: April 2003

AbstractAlprenolol (1‐(o‐allylphenoxy)‐3‐isopropylamino‐2‐propanol), a drug which is used in the management of cardiovascular diseases, was copolymerized with acrylamide. The incorporation of alprenolol into the copolymer decreased its potency for binding to beta‐adrenergic receptors located on membranes of frog erythrocytes a thousand times. However, this incorporation decreased the potency of alprenolol for binding to antibodies specific for catecholamines and alprenolol‐related drugs only about three times. The incorporation of the drug into the polymer apparently results in steric strains preventing the approach of the drug residues to sterically constrained receptor binding sites, but allowing its approach to the accessible antibody binding sites. Copolymerization with acrylamide was used to prepare the polymer bound form of another drug which contains an allyl group, an alpha‐adrenergic antagonist, azapetine (6‐allyl‐6,7‐dihydro‐5H‐dibenz[c,e]azepine).
Study of the influence of stabilizers, metals, and peroxides on the thermo‐oxidative degradation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene)
Authors: Sláma Zdeněk , Mayer Josef 
Published: April 2003

AbstractThe authors have studied the influence of some stabilizers, trace amounts of cupric and ferric compounds, and peroxides on the thermo‐oxidative degradation of poly(oxy‐2,6‐dimethyl‐1,4‐phenylene). It was found that phenolic antioxidants, didodecyl 3,3′‐thiodipropionate, and phosphorous acid esters do not exhibit a stabilizing effect. 2‐Benzimidazolethiol, 2‐benzothiazolethiol, and hexamethylphosphoric triamide were found to be retardation agents. Based on these results a mechanism of the degradation process is proposed.
Photopolymerization of methyl methacrylate in bulk and in pyridine diluted systems with pyridine‐sulfur dioxide complex alone and in combination with benzoyl peroxide as photoinitiators
Authors: Ghosh Premamoy , Biswas Samir 
Published: April 2003

AbstractIt was found that the Py‐SO2 complex (4–140 mmol·1−1) initiates the photopolymerization of methyl methacrylate (MMA) in bulk at 40°C, the initiator exponent, k/kt, and the monomer exponent being 0,30, 1,27·10−2 1·mol−1·s−1, and 1,00, respectively. The radical generation is followed by an in‐situ initiator‐monomer complexation reaction. The kinetics of the photopolymerization of MMA were also studied using the (Py‐SO2)‐complex (0,01–0,35 mol·1−1) in redox combination with benzoyl peroxide (BZ2O2) (2 − 110 mmol·1−1) as initiator in the presence of variable concentrations of pyridine (1 − 7 mol·1−1). The initiation depends on the concentrations of all the reactants in the system, and the reaction order with respect to either component of the redox pair is equal to 0,5 or reasonably less than 0,5, depending on whether or not the initiating component in question is present in the system in excess compared to its counterpart in the redox combination. Variable monomer exponents, largely dependent on [BZ2O2], characterize the redox photopolymerization process. The monomer exponent value, unity at [BZ2O2] = 0, progressively decreases with increasing [BZ2O2] (non‐ideal kinetics). The rate enhancing effect of the solvent pyridine is more prominent at higher [BZ2O2]. The kinetic nonidealities in each case were further analyzed and interpreted in terms of (a) primary radical termination and (b) degradative initiator transfer. Relative effects of the variation of the level of dilution with pyridine were also analyzed.
The influence of interaction between constituent blocks on conformation of the ABA type 2‐hydroxyethyl methacrylate/styrene block copolymer in a solvent mixture
Authors: Ikemi Masahisa , Watanabe Tatsuya , Okano Teruo , Shinohara Isao 
Published: April 2003

AbstractThe ABA type block copolymer of 2‐hydroxyethyl methacrylate (HEMA) and styrene was synthesized and the influence of the interaction between constituent blocks on the conformational change of the block copolymer was investigated in mixtures of DMF and 1,4‐dioxane which are selective solvents for poly(HEMA) and polystyrene, respectively. The intrinsic viscosity [η] of the mixture from the parent homopolymers of the block copolymer was compared with the value calculated on assuming lack of interaction between unlike segments. The [η] value at 15°C was found to agree with the calculated value despite of incompatibility between dissimilar segments. On the contrary, the [η] value at 30°C deviated positively from the theoretical value, especially in N,N‐dimethylformamide (DMF) or 1,4‐dioxane‐rich solvents, indicating that hetero contact between unlike segments at elevated temperature results in an increase of the average hydrodynamic volume because of repulsive interaction. The molecular expansion was found to become large with an enhancement of incompatibility. The same kind of transition versus temperature was observed in the intrinsic viscosity curve of the block copolymer, suggesting that hetero contacts between dissimilar segments occur at elevated temperature and that enhancement of solvent selectivity results in a conformational change of the block copolymer. A further increase of the solvent selectivity toward the polystyrene blocks was found to lead to intermolecular association of the block copolymer through aggregation of the poly(HEMA) side blocks.
Eine neue methode zur ermittlung kinetischer und kalorischer daten einer radikalischen copolymerisation, 2. Verbesserte auswertungsmethode am beispiel des systems 2‐hydroxyethylmethacrylat/methylmethacrylat
Authors: Fink Johannes Karl 
Published: April 2003

AbstractThe monomer reactivity ratios and the ratio of the rate constants of termination in the 2‐hydroxyethyl methacrylate/methyl methacrylate system were measured by differential thermal analysis. The data for the monomer reactivity ratios agree well with data calculated from the Q‐e scheme.
Polymerization reactivity of styrene complexes composed of maleic anhydride, p‐chloranil or 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone
Authors: Iwatsuki Shouji , Itoh Takahito , Hiraiwa Akihiko 
Published: April 2003

AbstractTerpolymerizations of styrene (St)/p‐chloranil (PCA)/maleic anhydride (MAnh), St/2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ)/MAnh, and St/DDQ/PCA systems were studied, in order to compare the reactivities as acceptor monomers among MAnh, PCA, and DDQ. These terpolymerizations were treated by the complex mechanism. The modified and real monomer reactivity ratios of the complexes in these systems were obtained as rI(KI/KII) (PCA‐St) = 1,60 and rII(KII/KI) (MAnh‐St) = 0,10, rI(PCA‐St) = 3,55 and rII(MAnh‐St) = 0,045, rI(KI/KII) (DDQ‐St) = 50 and rII(KII/KI) (MAnh‐St) = 0,01, rI(DDQ‐St) = 132 and rII(MAnh‐St) = 0,0038, and rI(KI/KII) (DDQ‐St) = 200 and rII(KII/KI) (PCA‐St) = 0,001, rI(DDQ‐St) = 238 and rII(PCA‐St) = 0,0008, respectively. The reactivity of these St complexes was concluded to be controlled primarily by the polarity of the acceptor monomers.
Reactivity of growing radical in the copolymerization of styrenes with oxygen in the presence of cobalt complex
Authors: Nukui Masahiro , Ohkatsu Yasukazu , Tsuruta Teiji 
Published: April 2003

AbstractCopolymerizations of a styrene homologue with oxygen were carried out in the presence of a Co(II) (Schiff‐base) complex having a chiral ligand. The metal complex showed a retarding effect on the rate of oxygen absorption in the reaction due to its interaction with growing radicals. Main product was almost an equimolar copolymer of monomer and oxygen, in the case of styrene and α‐methylstyrene. On the other hand, trans epoxide as well as a copolymer having many ether units were formed in the reaction of β‐methylstyrene. The presence of the cobalt complex increased the yield of epoxide and induced asymmetry in the epoxide.
Aggregation of poly(methacrylic acid)‐poly(ethylene oxide) complex in aqueous medium
Authors: Ohno Hiroyuki , Matsuda Hiro , Tsuchida Eishun 
Published: April 2003

AbstractIt is known that poly(methacrylic acid) and poly(ethylene oxide) interact with each other through hydrogen bonds and form polymer complexes in an aqueous medium. The initially formed polymer complexes were considered to exist in a semi‐stable state, and they aggregated through desolvation and hydrophobic interaction. A successive aggregation of polymer complexes was observed following the rapid initial complexation. The aggregation was affected by some chemical factors e.g., polymer concentration, temperature, pH and so on. These effects were measured as the changes of the molecular shape by means of laser‐light scattering, turbidity measurements, and scanning electron microscopy. It was observed that lower pH and higher temperature made the aggregation faster within such experimental conditions as pH 2–7, 20–50°C. The aggregates were nearly spherical with almost the same diameter (200 nm), and spontaneously grew larger with time.
New catalysts for the oxidative polymerization of 2,6‐dimethylphenol, 4. The crystal and molecular structure of tetrakis(tetrabutylammonium) hexakis(2,2‐dicyano‐1,1‐ethenedithiolato)octacuprate(i), tetrakis(tetrabutylammonium) hexakis‐(1,2‐dicyano‐1,2‐ethenedithiolato)octacuprate(i), and hexakis[copper(i)‐n,n‐diethylthiocarbamate]
Authors: Dietrich Hans , Storck Winfried , Manecke Georg 
Published: April 2003

AbstractThe X‐ray determination of the crystal structures shows that the dicyanoethenedithiolatocopper(I) complexes [N(C4H9)4]4[Cu8(S2CC(CN)2)6] (1) and [N(C4H9)4]4[Cu8(S(CN)CC(CN)S)6] (2) contain cube‐shaped Cu8‐clusters, whereas the Cu(I)‐N,N‐(diethyl)thiocarbamate complex (3) contains a Cu6‐octahedron in its centre. A common feature of the three complexes is the coordination of each copper atom by three donor atoms having suitable empty orbitals for back‐donation. This results in flat pyramidal arrangements with the basal plane of the three donor atoms being outside the cluster. All clusters deviate significantly from their ideal symmetry. In complex 2 the Cu8‐cube is tetragonally elongated and the CuCu‐distances are in general much larger (3,20 and 3,70 Å, respectively) than in other comparable complexes. Moreover, its anions are fitted into cages of a pseudocubic hydrophobic matrix formed by the tetrabutylammonium cations. It is concluded that is is the bonding within the coordination pyramids of the copper atoms which stabilizes the clusters, whereas the bonding within the clusters seems to be of comparably small importance.
Télomérisation de l'isobutylène
Authors: Taha Mohammed , Rigal Gérard , Piétrasanta Yves , Platzer Nicole , Sudres Pierre , Raynal Serge 
Published: April 2003

AbstractThe telomerization of isobutene was investigated using redox catalysis, free radical, and particularly cationic initiation. The influence of the initiator on the degree of polymerization and the structure of the telomers was studied. Redox and free radical telomerization with CCl4 and CCl3Br were found to permit synthesis and identification of the monoadduct structure. Cationic telomerization gives regular structure compounds and the molecular weights are higher than those obtained by other methods of telomerization.
Recherche de télomères à activité pharmacologique potentielle, 3. Préparation et toxicologie de supports télomères à fonctions hydroxyles
Authors: Bauduin Gérard , Bondon Daniel , Martel Jacques , Pietrasanta Yves , Pucci Bernard , Serrano Jean‐Jacques , Francois Colette 
Published: April 2003

AbstractSeveral telomers of vinyl alcohol with chloroform and diethyl phosphonate were prepared. Their DPn were measured by several analytical methods (elemental analysis, NMR spectroscopy, viscosimetry). Their small molecular size, their good water‐solubility, and their very low acute toxicity allow to use them as drug‐carriers in pharmacological applications.
Reaktive Träger auf der Basis von Polyethylenimin zur Immobilisierung von Enzymen
Authors: Manecke Georg , Heydolph Sabine 
Published: April 2003

AbstractReactive slightly basic carriers with isothiocyanato and azido groups, which are able to bind enzymes covalently, could be obtained by reaction of crosslinked and uncrosslinked poly‐(ethyleneimine) with 4‐nitrophenyl isothiocyanate, 4‐nitrophenyl isocyanate, or ethyl chloroacetate, respectively, and subsequent reactions. The binding ability of the carriers for papain, trypsin, α‐chymotrypsin, and urease in dependence of the content of reactive groups and in the case of urease as function of the amount of offered enzyme was investigated. To characterize the immobilized enzymes some properties as enzymatic activity, storage stability, and stability after repeated application were determined.
Thermodynamic studies on poly(a) · poly(u) duplex‐dye systems
Authors: Tanaka Shigeyuki , Baba Yoshihiro , Kagemoto Akihiro , Fujishiro Ryoichi 
Published: April 2003

AbstractThe interaction between poly(A) · poly(U) duplex and dyes (proflavine (PF) and 9‐aminoacridine (9‐AA)) was studied by means of the heat of mixing. From the results, thermodynamic quantities of poly(A) · poly(U) duplex‐dye systems for the intercalation process were estimated. The free energy change for the poly(A) · poly(U) duplex‐(PF) system is smaller than that for the poly(A) · poly(U) duplex‐(9‐AA) system, indicating that PF intercalated into poly(A) · poly(U) duplex is more stable than the intercalated 9‐AA. This conclusion is based on the absolute value of the heat of interaction between PF and poly(A) · poly(U) duplex being larger than that between 9‐AA and the poly(A) · poly(U) duplex.
Kinetics of the anionic polymerization of tert‐butyl methacrylate in tetrahydrofuran
Authors: Müller Axel H. E. 
Published: April 2003

AbstractThe anionic polymerization of tert‐butyl methacrylate (TBMA) in tetrahydrofuran, using Na+ and Cs+ as counterions proceeds without side reactions even at room temperature. The resulting molecular weight distributions are nearly monodisperse (Mw/Mn ⩽ 1,01). The rate constants for the propagation of ion pairs were measured in the range from + 15 to −100°C. The Arrhenius plots are linear, but different for the two counterions, resulting in the following numerical values for the frequency exponent A and the activation energy Ea:

A = 8,5 and Ea = 7,2 kcal/mol = 30 kJ/mol for Na+;
A = 9,5 and Ea = 5,6 kcal/mol = 23 kJ/mol for Cs+.
The difference between the counterions, which is in contrast to the polymerization of methyl methacrylate (MMA), as well as the lower rate constants are not due to the steric factor of the tert‐butyl group but to its positive inductive effect which influences the structure of the propagating macroion pair by decreasing its reactivity. The relative reactivities of the PMMA and PTBMA ion pairs towards MMA and TBMA are estimated.