bluuebunny/crossref_metadata_2025 huggingface dataset:
Etude des propriétés électro‐optiques de l'ADN par biréfringence électrique à faible champ, 4. Influence des interactions ADN‐histones
Authors: Marion Christian , Roux Bernard
Published: April 2003

The interactions of DNA with histone complexes (H2A, H2B, H3, H4) were studied by lowfield electric birefringence measurements. Electro‐optical measurements revealed that histones induce a folding of the DNA molecules: with increasing ratio histones/DNA, the steady‐state birefringence and the orientational relaxation time decrease gradually. A contribution of a permanent dipole moment to the orientation mechanism appears, while the electrical polarizability decreases quickly without significant differences in the optical anisotropy factors.
Poly(Ferulic acid) by thionyl chloride activated polycondensation
Authors: Elias Hans‐Georg , Palacios Joaquin A.
Published: April 2003

Ferulic acid (= 4‐hydroxy‐3‐methoxycinnamic acid) was condensation polymerized at temperatures between 0 and 50°C in bulk or various solvents, using thionyl chloride as activator in the presence or absence of bases. Depending on reaction conditions, true relative yields up to 100% and reduced viscosities (at 0,005 g/mL solute concentration) up to 96 mL/g were observed. The polycondensation follows a 2‐stage kinetics.
Effect of thermodynamic strength of solvent on structure formation of crosslinked copolymers
Authors: Krakovyak Mark , Ananieva Tatiana , Anufrieva Elisaveta , Nekrasova Tatiana , Sinitsina Galina
Published: April 2003

The effect of the thermodynamic strength of the solvent used in the copolymerization of mono‐ and bifunctional monomers on the molecular‐topologic structure of soluble copolymers with bridge bonds was investigated. The investigation was carried out taking as an example radical copolymerization of methyl methacrylate (MMA) and 9,10‐anthrylenedimethyl dimethacrylate. The presence of anthracene groups in the molecules of the crosslinking agent made it possible to follow the number of intra‐ and interchain bridge bonds formed in the polymer system. Toluene/octane mixtures with an octane content from 0 to 35 vol.‐% were used as solvents of different thermodynamic strengths with respect to PMMA. It was found that over a narrow range of changes in the composition of the solvent (from 30 to 33 vol.‐% of octane) the values of M̄n and [η] of the copolymers increase drastically. It is shown that this increase is due to an increase in the number of interchain crosslinks occurring when the strength of the solvent under the copolymerization conditions used decreases.
Large deformation of hydrogels of poly(vinyl alcohol), agarose and kappa‐carrageenan
Authors: Watase Mineo , Nishinari Katsuyoshi
Published: April 2003

The deformation behaviour of hydrogels of poly(vinyl alcohol) (PVA), agarose and kappa‐carrageenan was investigated and compared with each other. PVA gels prepared by periodically repeated freezing‐thawing cycles showed a much larger breaking force and breaking deformation than agarose and kappa‐carrageenan gels.
Photo‐sensitized oxidation of styrene‐butadiene copolymer. Role of singlet oxygen
Authors: Nowakowska Maria
Published: April 2003

The potosensibilization effect of anthracene and its substituted derivatives on the oxidation of styrene‐butadiene copolymer (SBR) was investigated. The potosensitized oxidation of SBR is explained on the basis of a reaction between singlet oxygen and the copolymer.
Studies on electrochemically prepared oxidized polypyrrole salt films
Authors: Bi Xiangtong , Yao Youxin , Wan Meixiang , Wang Ping , Xiao Ke , Yang Qiyung , Qian Renyuan
Published: April 2003

It was found that oxidized polypyrrole (PPy) film, electrochemically polymerized from aqueous H2SO4 solutions, shows correct stoichiometry in the mole ratio C : H : N, although still containing a large amount of oxygen. The apparent density of the film obtained was close to its flotation density of 1,514 g/cm3. Morphology studies by SEM showed an aggregation of ca. 1 μm properties into hollow bowls of 30 μm diameter in the case of PPy‐BF4, PPy‐PF6 and PPy‐CIO4 films, electrochemically prepared from CH3CN (1% H2O) solutions, while a PPy‐HSO4 film from aqueous solution gave a much smoother film surface and no hollow bowls. Interesting morphology was observed for the growth of electrochemically oxidized PPy in CH3CN solution on a wire net anode of 27 × 27 μm2 holes. The nucleation of the oxidized PPy growth was found to be always initiated at the mid‐points of the four sides of the square holes so that regular arrays of hollow bowls resulted. In aqueous H2SO4 solution the oxidized PPy grew on the surface of the net wires. Besides particles of ca. 0,3 μm diameter numerous solid blocks of 5 μm size with sharp edges were observed. The metallic temperature dependence of the conductivity of various oxidized PPy films was demonstrated by voltage shorted compaction (VSC) measurements, while a partially electrochemically reduced PPy‐BF4 film showed a broad maximum in VSC conductivity around 100 K.
Heat capacity of semicrystalline, linear poly(oxymethylene) and poly(oxyethylene)
Authors: Suzuki Hidematsu , Grebowicz Janusz , Wunderlich Bernhard
Published: April 2003

The heat capacities of 38 semicrystalline poly(oxymethylene)s and poly(oxyethylene)s were determined by differential scanning calorimetry from 205 K through the melting transition. By comparison with the well known limiting heat capacities of the supercooled liquids and the crystals of the macromolecules it was found that there are negative and positive deviations from additivity of the heat capacities with crystallinity between the glass transition and the melting transition. The negative deviations are linked with “rigid amorphous” material, and the positive deviations were previously linked to defect formation or early melting. The rigid amorphous fraction in poly(oxymethylene) is constant up to the melting region, in contrast to polypropylene, where it is decreasing with temperature. The proposed mesophase transition in poly(oxymethylene) is shown to be a minor effect. The poly(oxyethylene) heat capacity is governed by positive heat capacity deviations within the rather short temperature range between glass transition and melting.
Structure determination by two‐dimensional NMR of α‐hydro‐ω‐butyloligostyrenes fractionated by liquid chromatography
Authors: Ray G. Joseph , Pauls Richard E. , Lewis Jerry J. , Rogers Lockhart B.
Published: April 2003

Two aspects of the reversed‐phase liquid chromatographic separation of α‐hydro‐ω‐butyloligostyrene stereoisomers are presented. In the first part, two‐dimensional NMR is employed to make stereochemical assignments on isolated dimer, trimer and tetramer species. This work established the elution pattern of the stereoisomers as isotactic, heterotactic and syndiotactic for tetramers. In the second part, the elution behavior of these stereoisomers in reversed‐phase chromatography is compared to that observed in size exclusion chromatography, and these comparisons suggest that differences in the effective sizes of the stereoisomers are important factors in their separation.
Water‐insoluble polyacrylamide, 1. Syntheses and characterization of polymers from acryloylaminobenzoic acids
Authors: Patel Kishore , Desai Trushar , Suthar Bhikhu
Published: April 2003

2‐, 3‐ and 4‐Acryloylaminobenzoic acids were prepared in overall yields of 72, 78 and 83%, respectively. Radical polymerizations of all three monomers were studied using 2,2′‐azoisobutyronitrile as initiator in 1,4‐dioxane at three different temperatures. The unfractionated polymers were characterized by their physical properties, IR and NMR spectral studies, viscosity measurements and vapour pressure osmometry. The thermal properties were elucidated by thermogravimetry.
Polyoxirannes et polythiirannes comportant un centre chiral dans la chaîne latérale, 3. Polymérisation de (2RS,3S)‐ et (2R,3S)‐épithio‐1,2 méthyl‐3 pentanes
Authors: Goguelin Michel , Sepulchre Maurice
Published: April 2003

Different mixtures of (2R,3S)‐ and (2S,3S)‐1,2‐epithio‐3‐methylpentanes (1) were polymerized using anionic (sodium), stereoselective (ZnEt2/H2O, cadmium tartrate) and stereoelective (ZnEt2/R(−)‐3,3‐dimethyl‐1,2‐butanediol (R(−)DMBD)) initiator systems. In all cases a preferential consumption of the (2R,3S)‐diastereoisomer was observed. The reactivity ratios of the two diastereoisomers (2R,3S) and (2S,3S) in the copolymerization, initiated with sodium, were determined: r1 = 1,40 ± 0,08 and r2 = 0,54 ± 0,05. A low but significant diastereoisomeric enrichment was observed in stereoselective polymerization. It results from different consumption rates for the two diastereoisomers on enantiomorphic sites of the initiator. The election obtained with a stereoelective system is much higher. It is, however, not very different from that observed with isopropylthiiranne, which does not bear an additional chiral center in the alkyl substituant.
Study of exchange reactions in polycarbonate/polyarylcarboxylate mixtures with model compounds
Authors: Devaux Jacques , Devaux Pierre , Godard Pierre
Published: April 2003

The exchange reaction between a polycarbonate and a polyarylcarboxylate, both based on bisphenol A, was simulated by studying the reaction between the polycarbonate and diphenyl terephthalate or isophthalate used as model compounds of a polyarylcarboxylate. The kinetic results indicate the presence of a transesterification reaction occurring without any catalyst. Some results from reactions in the melt between both polymers also point to an exchange reaction.
A non‐linear approach to the Kuhn‐Mark‐Houwink‐Sakurada equation
Authors: Jadraque Daniel , Pereña José M.
Published: April 2003

Intrinsic viscosities and molecular weights were evaluated to obtain Kuhn‐Mark‐Houwink‐Sakurada (KMHS) relationships for some selected polymers by means of a non‐linear regression analysis. The proposed method yields unbiased values of the KMHS parametersaandK, improves the fitting and shows that KMHS relationship must be considered as a simple correlation with two interdependent parameters,aandK.
Polymer conformation and viscometric behaviour, 3. Synthesis, characterization and conformational studies in poly(mono‐n‐octyl itaconate)
Authors: Gargallo Ligia , Radić Deodato , León Arturo
Published: April 2003

The unperturbed dimensions and the steric factor σ of poly(mono‐n‐octyl itaconate) (poly‐(1‐carboxy‐1‐octyloxycarbonylmethylethylene)) were determined from the intrinsic viscosities in two solvents, using the semiempirical equation of Stockmayer and Fixman. Evidence for the existence of specific effects was found. The irregular behaviour observed, can be interpreted in terms of conformational changes and conformational transitions of the polymeric chain, induced both by solvent and temperature. The effect of the structure of the monomeric unit on the flexibility of the macromolecule is discussed.
Synthèse, étude physicochimique et diélectrique de poly(acétoxyméthylstyrène)s
Authors: Amadei Henri , Monthéard Jean‐Pierre , Boiteux‐Steffan Gisèle , Lucas Jean‐Michel , Seytre Gérard
Published: April 2003

Various poly(acetoxymethylstyrene)s were synthesized. Examination of the physicochemical properties of the polymers as a function of the type of substitution revealed the influence of the position of polar groups on the thermal (glass transition temperature) and electrical (dielectric constant and loss factor) characteristics of the polymers. Because of their good solubility and their electrical properties over a wide range of temperatures and frequencies the polymers proved to be interesting materials for dielectric films.
Studies on functional diene oligomers with an amino end group, 2. Reaction mechanism of the isoprene oligomerization
Authors: Nagasaki Yukio , Yoshino Norio , Tsuruta Teiji
Published: April 2003

Lithium diisopropylamide, in the presence of diisopropylamine, initiates the polymerization of isoprene to form oligomers having one diisopropylamino end group. These oligomers 1 a, formed in the early stages of the reaction, are considered to carry out the chain termination (or metalation) reaction. Results of mechanistic studies of the chain termination (or metalation) reaction in isoprene oligomerization in the presence of various types of allylamine homologues, as low molecular weight model compounds for 1 a are presented. The presence of a cis‐methyl group with respect to the amino methylene group was found to be essential for the low molecular weight model compounds to exhibit large reactivity in the chain transfer reaction. Oligomers with amino end groups neither have to possess a cis‐methyl group nor an allylamine structure to be active. A number of results showed that the driving force for the metalation reaction of oligomers with amino end groups is different in nature from that of the lowmolecular‐weight allylamine homologues. A possible mechanism for the metalation reaction of these oligomers is discussed in terms of a hydrophobic interaction with the growing chain.
Action du sec‐butyllithium sur le bis(isopropényl‐4 phényl)‐1,1 phényl‐1 tridécane en milieu solvant non‐polaire
Authors: Beinert Gérard , Zilliox Jean‐Georges , Herz Jean
Published: April 2003

The reaction of sec‐butyllithium with 1,1‐bis(4‐isopropenylphenyl)‐1‐phenyltridecane (3) yields carbanionic species which are soluble in a non‐polar solvent. The long hydrocarbon “tail” of the molecule and the tendency of the organolithium compounds to associate may be the reason for the high solubility, possibly due to micel‐formation. In the absence of any sidereaction, the addition reaction should lead to a difunctional organolithium compound. However, UV spectrometric measurements and characterization by size exclusion chromatography of the species obtained after protonation of the anionic sites, show that oligomerization accompanies the di‐addition reaction with formation of principally dimeric and a small fraction of trimeric molecules. This implies the existence of di‐, tri‐ and tetracarbanionic species in the “living” reaction media.
Synthèse par voie radicalaire de polymères à extrémités hydroxylées, 14. Synthèse de copolymères butadiène‐vinylferrocène
Authors: Brosse Jean‐Claude , Folliot Véronique , Legeay Gilbert , Raynal Serge , Doriath Gérard
Published: April 2003

Hydrogen peroxide, thermally cleaved into hydroxyl radicals, was used as initiator of butadiene‐vinylferrocene copolymerization. The influence of different parameters like temperature, pressure, proportion of hydrogen peroxyde and addition of a solvent with weak transfer capability was studied.
Immobilization of α‐chymotrypsin on poly(methyl methacrylate‐co‐acrylic acid) core‐shell latex
Authors: Bahadur Anita , Bahadur Pratap , Riess Gérard
Published: April 2003

Core‐shell latex of poly(methyl methacrylate‐co‐acrylic acid) with surface containing functional carboxylic acids, was prepared by seed polymerization and characterized. α‐Chymotrypsin was immobilized on the surface of these latex particles by chemical bonding in aqueous medium, using a water soluble carbodiimide as coupling agent. The latex particles size before and after the attachment of the enzyme was determined using photon correlation spectroscopy. The activities of free and immobilized enzyme were studied as a function of temperature, reusability and pH. The activity for the immobilized enzyme was highest at a pH slightly higher than the optimum pH of free enzyme, which could be explained due to the polyanionic matrix as well as due to the variation in the size of latex at higher pH, which provided more mobility to the enzyme, and thus a higher activity.
Kinetik der copolymerisation von styrol und p‐jodstyrol
Authors: Braun Dietrich , Chaudhari Dinkar , Czerwinski Wojciech
Published: April 2003

A study of the copolymerization behaviour of styrene (M1) and p‐iodostyrene (M2) was carried out at 50°C in bulk with azoisobutyronitrile as initiator. The monomer reactivity ratios calculated according to Kelen‐Tüdős are r1 = 0,629 ± 0,109; r2 = 0,965 ± 0,153. Kinetic measurements were performed dilatometrically. Contraction constants for both homopolymerizations were determined to be K11 = 0,172 and K22 = 0,130. The applicability of the Wittmer method for contraction constant calculations was verified. The contraction constants for the alternating copolymerization step was estimated to be K12 = 0,132. Contraction constants calculated with this value are very adequate to the experimental data. Kinetic homopolymerization constants δ = k11//kp were found by molecular weight measurements as δ1 = 60,99 and δ2 = 11,40 (mol · s/1)1/2, respectively. Initiator efficiency factors are f = 0,60 (for M1) and 0,25 (for M2). The Polymerization rate can be described as a function of the composition of monomer mixture by the classical Melville equation with cross termination constant Φ = 0,338.
Cinétiques de télomérisation, 6. Détermination des degrés de polymérisation a partir de la répartition moléculaire
Authors: Boutevin Bernard , Maliszewicz Marc , Piétrasanta Yves
Published: April 2003

It is shown that the kinetic laws established for polymerization reactions can be applied for telomerization reactions provided the number‐average degrees of polymerization DPn are greater than ten. For DPn > 10 it is necessary to calculate the molecular distributions. Values of DPn obtained with the method of Mayo and the molecular distribution method are compared and an experimental application is given by the radical‐initiated telomerization of glycidyl methacrylate (2,3‐epoxypropyl methacrylate) with bromotrichloromethane.
Ring‐opening polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane
Authors: Endo Takeshi , Yako Naoto , Azuma Kazumi , Nate Kazuo
Published: April 2003

Photochemical and radical polymerization of 2‐methylene‐4‐phenyl‐1,3‐dioxolane (1) were carried out leading to the same polyester 2. By radical copolymerization of 1 with methyl methacrylate using various mole ratios of the monomers, the corresponding copolymers with various contents of ester groups in the backbone were obtained.
Polyene formation and crosslinking during the thermal degradation of poly(vinyl chloride)
Authors: Leijenaar Steven R. , van den Heuvel C. Jurriaan M. , Huysmans Willem G. B.
Published: April 2003

Polyvinyl chloride (PVC) was degraded at processing temperatures in an inert atmosphere. The samples were analyzed by means of a size exclusion chromatograph equipped with a differential refractometer and a photo‐diode array UV‐visible detector. This enabled us to record online the presence of polyenes at different positions along the molecular weight distribution of the degraded polymer. Polyenes proved to be concentrated on the low molecular weight side of the distribution and, more specifically, on the high molecular weight side, which had been broadened upon degradation. The results indicate that low molecular weight PVC degrades relatively fast and that PVC molecules containing polyenes crosslink easily.
Study of photopolymers, 25. Photochemical reaction of dilute solutions of polymers containing pendant cinnamic ester moieties and photosensitizing groups
Authors: Nishikubo Tadatomi , Uchida Jiro , Takahashi Eiji , Iizawa Takashi
Published: April 2003

Rates of photochemical reactions of polymers containing pendant cinnamic ester moieties and photosensitizing 4‐nitrophenoxy or 4‐nitro‐1‐naphthyloxy groups were determined in dilute benzene and tetrahydrofuran solutions. The rate of photodimerization of the polymers obeys first order kinetics in diluted solution and is affected by the type and content of pendant photosensitizing groups and by the structure of the polymer skeleton. By comparison of the rate of photodimerization of three homopolymers and six copolymers, it could be concluded that the polymers consisting of flexible segments have a higher rate of photodimerization than those made of rigid segments.
Polyarylenealkenylenes and polyheteroarylenealkenylenes, 17. Syntheses of alkoxylated poly(2‐nitro‐1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s and poly(2,5‐dimethoxy‐1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s, and study of their electrical conductivity
Authors: Koßmehl Gerhard , Samandari Massoud
Published: April 2003

The influence of different substituents (nitro and methoxy groups) on the physical properties — fusibility and solubility — and the electrical conductivity of alkoxylated poly(1,4‐phenylenevinylene‐1,4‐phenylenevinylene)s (9, 10, 12 and 13) and of the corresponding model compounds (15, 16, 18 and 19), were studied. The conductivity at room temperature, σ298K, was found to be generally increased for polymers with nitro substituents by 2–3 orders of magnitude and for dimethoxy substituted polymers up to 4 orders of magnitude, as compared with the unsubstituted polyvinylenes. Iodine doped polyvinylenes show as an average d. c. electrical conductivities 2 orders of magnitude higher than those of the original polymers.
Benzil/triethylamine combination as photoinitiator for methyl methacrylate polymerization
Authors: Sengupta Pranab Kumar , Modak Sadhan Kumar
Published: April 2003

Photopolymerization of methyl methacrylate (MMA) in bulk and in solution was studied using the combination benzil (BZL)/triethylamine (TEA) as photoinitiator. The initiation was found to occur through photoreduction of the ketone in presence of an amine via exciplex formation. A kinetic study of the polymerization showed that both carbonyl groups of benzil are involved in exciplex interaction, resulting in diradical formation. An analysis of the initiator dependent termination process revealed that primary radical termination is predominant in the particular system compared to the degradative initiator transfer. A kinetic scheme was designed to account for the various wastage reactions occurring in the polymerization system.
Biocide polymere, 12. Synthese und hydrolyseverhalten von copolymeren aus methacryl‐ und acrylsäure sowie 1‐methacryloyl‐ und 1‐acryloyl‐3‐methylpyrazol
Authors: Hartmann Manfred , Bauer Hans‐Jürgen , Fritzsche Antje , Wermann Kurt
Published: April 2003

The radical copolymerization of 1‐acryloyl‐ and 1‐methacryloyl‐3‐methylpyrazole (1a and 1b) with acrylic acid or methacrylic acid in solution was studied. Copolymers containing carboxyl as well as 3‐methyl‐1‐pyrazolylcarbonyl groups as side chains were prepared via the reaction of 3(5)‐methylpyrazole with activated poly(acrylic acid)s of various molecular weights. The hydrolysis data suggest that the release rates of the biocide 3(5)‐methylpyrazole from the investigated copolymers vary significantly depending on the content of carboxyl groups and their change during the hydrolysis.
Synthesis and characterization of a rubber incorporated polyamideimide
Authors: Sen Debasish , Bhakta Ramesh C. , Maiti Mrinal M. , Maiti Sukumar
Published: April 2003

A new flexible and crosslinkable copolyimide was prepared by low temperature polycondensation between bis [4‐(4‐chloroformylphthalimido)phenyl] ether (1), bis(4‐aminophenyl) ether and liquid α,ω‐bis[2‐(4‐piperazinyl)ethylaminocarbonyl]poly(butadiene‐co‐acrylonitrile) in DMAc solution. The polymer is soluble in DMF, DMAc, NMP, m‐cresol, DMSO and concentrated sulfuric acid. On heating with or without dicumyl peroxide the polymer was crosslinked.
Photostability of trityl salts with different anions in vacuo
Authors: Toncheva Veska D. , Velichkova Rumyana S.
Published: April 2003

The visible light‐induced photolysis of trityl salts with different anions was investigated in vacuo. The following order of photostability, determined from the rates of decoloration of the dichloroethane solutions of these salts, was found: (C6H5)3C+PF6− > (C6H5)3C+AsF6− > (C6H5)3C+BF4− > (C6H5)3C+SbCl6− ≥ (C6H5)3C+FeCl4−. By model reactions it was proved that the 9‐phenylfluorenyl cation, formed on irradiation as a main product in the early stage of the photolysis, takes part in the regeneration of (C6H5)3C+. The changes in electronic spectra, as well as the composition of the reaction mixtures after photolysis and the model reactions, confirm some stages of the earlier proposed scheme.
Influence of electron‐donor‐acceptor complex formation on the melt viscosity of some poly(dimethylsiloxane)s
Authors: Zentel Rudolf , Wu Jishan , Cantow Hans‐Joachim
Published: April 2003

A series of poly(dimethylsiloxane)s was synthesized containing either electron donor or electron acceptor groups, statistically arranged along the polymer chain or only at the chain ends (telechelic polymers). Blending of the donor and acceptor modified statistical copolymers led to a strong increase of the melt viscosity as a consequence of complex formation. In contrast to this, complex formation had no significant influence on the viscosity in blends from telechelic polymers. This different behaviour seems to be caused by the different molecular architecture favouring crosslinking by complex formation for the statistical copolymers and a linear chain extension for the telechelic polymers.
1H NMR study of the chitin dissolution mechanism
Authors: Vincendon Marc
Published: April 2003

The 1H NMR spectra of N‐acetyl‐D‐glucosamine (1) and methyl‐B‐D‐chitobioside (2), the monomer and dimer of chitin, respectively, were determined in the aprotic solvents, N,N‐dimethylacetamide (DMA) and DMA containing lithium chloride. It could be shown that dissolution of 1 and 2 in DMA/LiCl proceeds via interaction of one LiCl molecule with each labile proton (OH or NH). Observation of the temperature‐dependent hydroxyl proton chemical shift revealed the particular behaviour of the OH3 hydroxyl of 2. This dependence was assigned to the existence of an intramolecular hydrogen bond between OH3 and O5′ (the heterocyclic atom) of the other D‐glucopyranosyl unit. Similar results were found for chitin in DMA/LiCl solution.
Light scattering and viscosity studies of poly(2‐vinylpyridine 1‐oxide) in some organic solvents at 25°C
Authors: Sakamoto Noriyuki , Tanaka Hitoshi , Yamaguchi Katsuya , Yoshida Masafumi , Arichi Shizuo
Published: April 2003

Light scattering in 2‐propanol and viscosity measurements in six good solvents were carried out at 25°C for fourteen fractions of poly(2‐vinylpyridine 1‐oxide) (P2VPO) with molar mass of (1,3–34,4) · 104 g · mol−1, which were synthesized by oxidizing poly(2‐vinylpyridine) with H2O2. The numerical values of the Mark‐Houwink‐Sakurada constants K′ and a and of the parameters K and B from the plots of Kamide‐Kawai, Kurata‐Stockmayer and Inagaki‐Ptitsyn as well as Stockmayer‐Fixman, were determined as well. The averaged characteristic ratio C∞ and steric factor σ for this polymer are 8,58 and 2,07, evaluated from K in each solvent except benzyl alcohol with the last plot. The value in benzyl alcohol is rather large and clearly shows the solvent dependence in K. Comparing this average value with those of similar polymers, it is concluded that the P2VPO chain acquires a compact coil structure. The solvent power was found to increase in the following sequence: chloroform < 2‐propanol < 1‐propanol < methanol ≤ 1‐butanol < benzyl alcohol, as judged from the B values.
Model compounds of poly(methyl methacrylate). Conformational structure of the dimethyl esters of 2,2,4‐trimethyl‐ and of 2‐methoxymethyl‐2,4‐dimethylglutaric acid. 13C NMR, 1H NMR and vibrational spectroscopic study
Authors: Doskočilová Danica , Schneider Bohdan , Štokr Jan , Ševčík Stanislav , Přádný Martin , Lochmann Lubomír
Published: April 2003

The conformational structure of the dimethyl esters of 2,2,4‐trimethylglutaric acid, and of the erythro‐ and threo‐isomers of 2‐methoxymethyl‐2,2,4‐dimethylglutaric acids was studied by NMR and vibrational spectroscopic methods. Conformational structure generated by rotation about skeletal bonds was determined by analysis of vicinal coupling in 1H and 13C NMR spectra. The results are discussed in relation to the conformational structure of PMMA.
Deformation mechanisms of isotactic poly(1‐butene)
Authors: Yang Yong‐Chin , Geil Phillip H.
Published: April 2003

The deformation of thin films of poly(1‐butene) (PB) occurs by micronecking. In both fresh (From II crystal structure) and aged (Form I) films finite blocks are drawn off the edge of the microneck, the detailed mechanisms depending on the orientation of the original crystalline ribbons comprising the spherulites with respect to the draw direction. Deformation of fresh thick and thin PB films is accompanied by a transformation to a Form I which melts ca. 5°C lower than that obtained by aging alone (124 vs. 129°C); in thick films the molecular axes in the Form I crystals are oriented in a cone at about 30° to the draw direction until deformation is nearly complete, after which they align in the draw direction. Tensile properties depend on the crystal form, fresh samples having a considerably lower modulus and higher elongation to failure.
Polymerization of lactams, 75. Behaviour of the polymerization mixture prepared by the non‐activated polymerization of 2‐pyrrolidone above the limit polymerization temperature, 2
Authors: Fries Tomáš , Nováková Olga , Roda Jan , Králíček Jaroslav
Published: April 2003

The behaviour of the polymerization mixture of 2‐pyrrolidone (PD), i.e. of the mixture of polymer, monomer, and their potassium salts, obtained by non‐activated polymerization, was studied in the temperature region 170–180°C. Poly(2‐pyrrolidone) (PPD) was found to completely disappear at this temperature from the mixture, leading again to PPD under optimal polymerization conditions. The cycle, degradation‐polymerization, can be repeated without a substantial loss of the polymerization activity. A model polymerization mixture comprising PD, Potassium salt of PD and PPD, prepared beforehand, behaves similarly as the proper polymerization mixture.
Bifunctional anionic initiators: A critical study and overview
Authors: Bandermann Friedhelm , Speikamp Hans‐Dieter , Weigel Ludwig
Published: April 2003

The suitability of several dilithio compounds as initiators for the anionic polymerization of dienes was tested in view of the following criteria: quantitative reaction of diolefins withsec‐butyllithium within reasonable periods of time, precipitation of dilithio compounds in a heptane/toluene mixture, sufficient solubility of the dilithio compounds in toluene, rapid initiation of polymerization and small dispersion index of the polymer, low cost of the preparation of the diolefins and the dilithio initiators. The results show that with respect to the diolefins investigated the bifunctional initiator derived from 1,4‐bis(4‐(1‐phenylvinyl)phenyl)‐butane is most suited for the preparation of diene blocks in ABA‐triblock copolymers.
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

Polystyrene 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

The 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

This 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

The 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

In 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

The 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

Silica 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

Simulation 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

Polyurethanes (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

With 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

The 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

Polymers 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

The 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

A 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

The 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

A 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

Imogolite, 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

Nonlinear 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

The 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

Inulin 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.