bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymerization of macromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide) with various comonomers
Authors: Wicker Michael , Heitz Walter 
Published: April 2003

AbstractMacromonomers of poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were synthesized by reacting the monofunctional polymer with 4‐vinylbenzoyl chloride. The macromonomer was copolymerized with isoprene, butadiene, styrene, ethyl acrylate, and butyl acrylate. Reactivity ratios of 2,6‐dimethylphenyl 4‐vinylbenzoate (2) as a model compound were determined with styrene (St) and butyl acrylate (BA). The values obtained are rSt = 0,504, r2 = 1,233, and rBA = 0,123, r2 = 4,070. Polystyrene‐graft‐PPO is a one‐phase system with a Tg between those of the homopolymers. Tg's of the polyacrylate and PPO fractions are not changed by the composition of the polyacrylate‐graft‐PPO. DSC and dynamic mechanical measurements revealed that the polyacrylate‐graft‐PPO copolymers are phase‐separated if the molecular weight of the PPO macromonomer is high enough. In thermogravimetric analysis the polyacrylate‐graft‐PPO shows a two‐step weight, loss, one due to the polyacrylate at 380–390°C and another due to the PPO at 440–460°C.
Studies of the mechanism of the radical polymerization of vinyl acetate inhibited by furan compounds. Phenomenology and sensitivity analysis
Authors: Rieumont Jacques , Vega Rebeca 
Published: April 2003

AbstractThe classical treatment of inhibition in radical polymerization is complemented by a “sensitivity” analysis. This technique permits to establish which of the possible reactions are relevant or negligible to gain a better insight into the mechanism. The 2,2′‐azoisobutyronitrile (AIBN)‐initiated polymerization of vinyl acetate was studied in the presence of 5‐nitrofuroic acid and 3‐(2‐furyl)acrylic acid as inhibitors. The monomer dependence of the ratio of rate constants for the degradative transfer and chain propagation, ktrs/kp, and the values of the stoichiometric coefficients for these inhibitors were obtained and analyzed in the light of sensitivity analysis.
On the origin of the fluorescence emission of poly(ethylene terephthalate) by excitation at 340 nm
Authors: Chen Liusheng , Jin Xigao , Du Jinhuan , Qian Renyuan 
Published: April 2003

AbstractFluorescence emission of amorphous poly(ethylene terephthalate) films at wavelengths larger than that of the excimer emission was investigated. A film thickness dependence of the excitation spectra for 360 nm emission was observed. For thick films (e.g., 280 μm), their excitation spectra for 380–460 nm emission showed excitation peaks in the region of 320–360 nm, and the intensity ratio of the 370 nm emission (excited by 290 nm radiation) to the 390 nm emission (excited by 340 nm radiation) decreased with increasing thickness of the film. Apparently, the 370 nm emission (excimer) and the 380–460 nm emission originate from different species of the excited state. From the studies of model systems, dilute solutions of dimethyl terephthalate in CHCl3‐acetone and dimethyl terephthalate‐PMMA in CHCl3, it was found that the excitation at 340 nm is related to a \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \pi \limits^* $\end{document} ← n transition. Fluorescence emission from the S1 (n–\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \pi \limits^* $\end{document}) state and the interaction between the CO group and the phenylene π‐electrons results in the fluorescence in the 380–460 nm region.
Poly(methyl methacrylate)‐block‐poly(2,2‐dimethyltrimethylene carbonate); site transformation from a group transfer polymerization to an anionic ring‐opening polymerization
Authors: Hovestadt Wieland , Keul Helmut , Höcker Hartwig 
Published: April 2003

AbstractPoly(methyl methacrylate)‐block‐poly(2,2‐dimethyltrimethylene carbonate) was prepared by a group transfer polymerization (GTP) of methyl methacrylate (MMA), followed by an anionic metal‐free polymerization of 2,2‐dimethyltrimethylene carbonate (DTC). It was shown that the anionic metal‐free polymerization of DTC can be initiated either by the system silyl ether/tris(dimethylamino)sulfonium trimethylsilyldifluoride (TASF) or by the system 1‐methoxy‐1‐trimethylsilyloxy‐2‐methyl‐1‐propene (MTS) in combination with TASF. The latter can be considered as a model compound for the living PMMA end in a GTP polymerization. The transformation of the trimethylsilyl ketene acetal end into an anionic species was achieved by desilylation with TASF. In the presence of DTC the resulting enolate reacts as carbanion with the carbonyl group of the carbonate moiety. Thus, at the linkage of the two blocks a disubstituted malonic acid derivative is formed. GPC analysis of the copolymers reveals a unimodal and rather narrow distribution of molecular weights. The block structure expected from the way of preparation is confirmed by 13C NMR analysis. The 1H NMR analysis gives the composition of the block copolymers and reveals that the larger the PMMA block, the less efficient is the initiating ability, leading to a larger PDTC block as expected from the monomer to initiator ratio; correspondingly more homo‐PMMA is formed. Thermal analysis of the block copolymers shows a melting transition of the PDTC block which is by about 20°C lower than that of the homopolymer: the glass transition temperature of the PMMA block is hidden under the melting transition of the PDTC block.
Photo‐crosslinking of polymers bearing p‐(formylamino)‐styrene units
Authors: Shirai Masamitsu , Suzuki Masako , Saito Takayuki , Koyama Masaya , Tsunooka Masahiro 
Published: April 2003

AbstractPhotosensitive polymers were synthesized by radical copolymerization of p‐(formylamino)‐styreneIUPAC name: p‐vinylformanilide.
(1) with styrene (2), butyl methacrylate (3) or methyl methacrylate (4). On irradiation with 254 nm light the polymers become insoluble in solvents. Effects of the fraction of 1 units in the copolymers and of the polymers structure on the photoinduced insolubilization of the polymers were studied. The insoluble fraction of the exposed polymer films was enhanced by post‐heating. The quantum yield of the photolysis of 1 units in polymers was almost independent of the polymer structure. From model reactions employing formanilide, a mechanism of insolubilization of the polymers was discussed.
Synthèse et caractérisation de polystyrènes siliciés
Authors: Madit Nicolas , Bonfils Frédéric , Giral Louis , Montginoul Claude , Sagnes René , Schué François 
Published: April 2003

AbstractPoly(p‐trimethylsiloxystyrene) (1a), poly[p‐(tert‐butyldimethylsiloxy)styrene] (1b), poly[p‐(trimethylsiloxy)‐α‐methylstyrene] (1c), poly[p‐(tert‐butyldimethylsiloxy)‐α‐methylstyrene) (1d) and poly{p‐[2‐(tert‐butyldimethylsiloxy)ethyl]styrene]} (1e) were prepared by free‐radical or cationic polymerization of the corresponding monomers. Poly{[p‐[2(trimethylsiloxy)ethyl]styrene]‐co‐[p‐(2‐hydroxyethyl)styrene]} (2a) was synthetized by anionic polymerization of the corresponding trimethylsilylated monomer, followed by acid hydrolysis of the resulting polymer. Poly{[p‐[2‐(trimethylsiloxy)ethyl]styrene]‐co‐[p‐(tert‐butoxycarbonyloxy)styrene]} (2b) were prepared by free‐radical polymerization of the corresponding monomers.
Molecular weight control of linear polyethylenes prepared in gas phase with Ziegler catalysts
Authors: Pasquet Véronique , Spitz Roger 
Published: April 2003

AbstractLinear polyethylenes covering the range from high to low density were prepared in gas phase using an MgCl2‐supported Ziegler catalyst deposited on silica (bisupported catalyst). The comonomer used was 1‐butene. Molecular weights are dependent both on 1‐butene concentration and hydrogen pressure. The interaction of these two factors can be interpreted by the enhancement of the transfer reactions after 1‐butene insertion.
Some aspects of the reactivity of photo‐dimerizable esters grafted onto silicone main chain polymers
Authors: Coqueret Xavier , Achari Ahmida El , Hajaiej Adel , Lablache‐Combier Alain , Loucheux Claude , Randrianarisoa Lili 
Published: April 2003

AbstractThe reactivity under UV light and at room temperature of two series of photo‐crosslinkable silicone polymers containing pendant cinnamic or α‐cyano‐β‐styrylacrylicSystematic name: 2‐cyano‐5‐phenyl‐2,4‐pentadienoic.
(CSA) esters was examined by means of UV spectroscopy. Two types of behaviour were evidenced on the basis of qualitative spectrum observation and quantitative measurements of reaction rates. Polymers with trans‐cinnamic pendant groups were found to undergo during the first moments of 280 nm irradiation a fast photo‐isomerization, preceding the dimerization process which takes place with a smaller rate. The mobility of the reactive cinnamic chromophores attached to the highly flexible silicone main chain leads to a collision‐controlled process contrasting with the behaviour of the polymers containing more polar CSA esters. In this case, a clean dimerization with high reversibility suggests a matrix‐controlled process. This is supported by kinetic data indicating a levelled reactivity for several polymers containing different amounts of CSA esters.
Monte Carlo simulation of tetrahedral chains, 4. Size and shape of linear and star‐branched polymers
Authors: Zifferer Gerhard 
Published: April 2003

AbstractLinear and star‐branched chains with F = 4 − 12 arms and N = 125 − 7685 segments covering points of a tetrahedral lattice were generated by use of a pivot algorithm. For large N, the acceptance fractions f̄ of attempted moves may be described by a power law f̄ = A · (N − 1)−α. Clearly, the factor A decreases with increasing functionality F, but the exponent α is independent of the number of arms and equal to the value obtained for linear chains, α ≈ 0,1. Due to the influence of the hard‐core (centre) of the star, the acceptance fraction f̄ for small N is lower than predicted by the scaling law, yielding a stronger dependence on F than for large chains. Meansquare dimensions, i. e. mean‐square radius of gyration, mean‐square end‐to‐end distance and mean‐square centre‐to‐end distance obey a power law dependence on chain‐length (N − 1), the exponent being ≈ 1,184 for 245 ≤ N ≤ 7685 in all cases; alternatively, the (quadratic) dimensions may be described by a corrected scaling law (N − 1)2v · (C0 + C1 · (N − 1)−Δ) with v = 0,588 and Δ ≈ 0,5 as proposed by renormalization group theory for linear chains. The shape asymmetry of star‐branched polymers (with the same total number of segments each) decreases with increasing number of arms, but is still appreciable for F = 12, the highest number of arms examined.
Thermal reactions of amphotropic copolymers studied by thermogravimetry and temperature‐resolved pyrolysis‐field ionization mass spectrometry
Authors: Plage Bernd , Schulten Hans‐Rolf , Ringsdorf Helmut , Schuster Andreas 
Published: April 2003

AbstractThe thermal degradation mechanisms of amphiphilic acrylic copolymers containing mesogenic pyrimidine side chains and hydrophilic 2‐hydroxyethyl acrylate (HEA) main‐chain spacer units were investigated by thermogravimetry (TG) and pyrolysis‐field ionization mass spectrometry (Py‐FIMS). The degradation behaviour of these polymers depends on the amount of HEA incorporated. Thermogravimetry revealed that the main decomposition occurs in a single step for the pyrimidine homopolymer, whereas with increasing HEA content a two‐step process evolves. The major products identified by Py‐FIMS are two alcohols and one olefin split from the aromatic side chains. Depolymerization is only a minor degradation pathway. The rather complex thermal behaviour can be explained by three different reaction mechanisms: (a) alcohol formation via reaction of the HEA hydroxyl groups with ester groups in the side chains, (b) intramolecular cis‐elimination forming a volatile olefin and carboxylic acid groups remaining at the polymer backbone, and (c) the reaction of these acid groups with ester bonds forming the alcohols. Steps (b) and (c) are dominant for the pyrimidine homopolymer. With increasing HEA content in the copolymers step (a) becomes more important and, in addition, chemical crosslinking occurs. The mesogenic monomer, which was also examined, polymerized under the experimental conditions and showed essentially the thermal features of the pyrimidine homopolymer.
Novel degradable methacrylate‐ and p‐vinylphenoxy‐based oligomers, 1. Synthesis and characterization
Authors: Ericsson Jan , Hult Anders 
Published: April 2003

AbstractProcedures are presented for the synthesis of a series of dicarbonate oligomers with either methacrylate or p‐vinylphenoxy end‐groups as polymerizable units. In addition, the synthesis route is given for a novel precursor of p‐vinylphenoxy‐type carbonates, namely, p‐nitrophenyl 3‐p‐vinylphenoxypropyl carbonate. Polymerization of the new oligomers was studied by differential scanning calorimetry (DSC). The bis(p‐vinylphenoxy) dicarbonates were polymerized by thermally induced cationic polymerization, and the corresponding dimethacrylates by free‐radically initiated photopolymerization.
Batch emulsion copolymerization of butyl acrylate and methyl methacrylate in the presence of sodium dodecyl sulfate
Authors: Emlie Brigitte , Pichot Christian , Guillot Jean 
Published: April 2003

AbstractKinetics of batch emulsion copolymerization of butyl acrylate (BuA) with methyl methacrylate (MMA) have been investigated using sodium dodecyl sulfate as emulsifier and the redox system potassium peroxodisulfate (K2S2O8)/sodium disulfite (Na2S2O5) as initiator. Latexes have been characterized with regard to their copolymer composition through 1H NMR analysis and particle size distribution by a quasi‐elastic light scattering (QELS) technique or transmission electron microscopy. The effect of the monomer feed composition on the average copolymer composition vs. conversion was first studied in order to derive emulsion reactivity ratios. However, simulation of experimental data based on monomer partitioning (due to the high water solubility of MMA) and particle swelling was better accounted for when considering bulk reactivity ratios together with polymerization in the aqueous phase (in addition to that in the main locus of the polymer particles). Then, the influence of several pertinent parameters, such as emulsifier concentration, amount of initiator, monomer‐to‐water ratio and addition of an organic solvent has been examined in relation to the actual polymerization mechanism.
Luminescent characteristics of tris(2,2′‐bipyridine)‐ruthenium(II) adsorbed in a silk fibroin membrane
Authors: Yoshimizu Hiroaki , Asakura Tetsuo , Kaneko Masao 
Published: April 2003

AbstractThe emission characteristics of the excited state of tris(2,2′‐bipyridine)ruthenium(II), Ru(bpy), adsorbed on a silk fibroin membrane is studied. The life time of the excited state of the adsorbed Ru(bpy) is unusually longer (1 000 ns) than that of Ru(bpy) in aqueous solution (598 ns). The excited state of the adsorbed Ru(bpy)32+ is quenched by oxygen when dipped in methanol, but not in water. The quenching by oxygen in methanol follows the Stern‐Volmer equation. The luminescent characteristics of the adsorbed Ru complex is discussed in terms of binding in hydrophobic domains composed of tyrosine residues of the protein.
On the rectilinearity of copolymers
Authors: Jung Bernd , Depner Michael 
Published: April 2003

AbstractThe expression “stiffness” of a polymer chain is shown to be ambiguous, and the use of the word “rectilinearity” is proposed to replace it in certain contexts. The influence of non‐uniform curvature on Kuhn length and mean‐square end‐to‐end distance of (co)polymers is studied using the frameworks of the freely‐rotating‐chain model and the Porod‐Kratky model. It is shown that every fluctuation around the given mean curvature of a chain increases its overall rectilinearity. Specifically, it is concluded that the rectilinearity increases with increasing fluctuation magnitude and with increasing separation of the different curvatures along the chain, i. e., it becomes greater in the order: alternating, random and block copolymer.
Some fundamental studies of the reaction of poly(vinyl alcohol) with alkyl chlorophosphates
Authors: Arranz Félix , Sánchez‐Chaves Manuel , Baena Francisco , Fontaine Laurent , Brosse Jean‐Claude 
Published: April 2003

AbstractThe modification reaction of poly(vinyl alcohol) with diethyl chlorophosphate and ethyl dichlorophosphate is studied in homogeneous phase using tertiary amines as catalysts. The structure of the modified polymers was determined by means of 1H and 31P{1H} nuclear magnetic resonance (NMR) spectroscopy as well as by chemical analysis. The structure of the polymers resulting from the reaction with diethyl chlorophosphate greatly depends on the reaction temperature as well as the catalyst. For lower reaction temperatures (≤25°C) only acyclic phosphate ester groups were observed. The activation energy was found to be 24,9 kJ/mol. The presence of cyclic phosphate ester groups was found, when higher reaction temperatures (>25°C) were used. These results can be interpreted considering the existence of transesterification reactions. Crosslinking structures were obtained in case ethyl dichlorophosphate was used instead of diethyl chlorophosphate.
Polymerization reaction with diphenylphosphoryl azide. Preparation of poly(α‐amino acid)s by direct polycondensation of α‐amino acids
Authors: Nishi Norio , Tsunemi Masahiko , Hayasaka Hideki , Nakajima Bun‐ichiro , Tokura Seiichi 
Published: April 2003

AbstractPolypeptides can be prepared by stirring an amino acid solution in the presence of diphenylphosphoryl azide (DPPA) and an adequate tertiary amine. Generally, 1,3 mol of DPPA and 2,3 mol of triethylamine per mol of amino acid gave the best result. Polymerization of various amino acids (Gly, Ala, Leu, Phe, Met, Glu(OBzl), Glu(OMe), Cys(Bzl), Ser(Bzl), His(Bzl), Lys(Z), Arg(Tos), Arg(NO2), Arg(Mts), etc.; cf. Tab. 2) in dimethyl sulfoxide, N,N‐dimethylformamide, 1,4‐dioxane, pyridine, etc. gave the corresponding polypeptides with molecular weights as estimated from their intrinsic viscosities between 3 000 and 16 000, in reasonable yields. The purity of the resulting polypeptides was confirmed by IR, elemental analysis and optical rotation measurements of their acid total hydrolysates.
Polymerization reaction with diphenylphosphoryl azide. Preparation of sequential polypeptides by direct polycondensation of peptides
Authors: Nishi Norio , Naruse Takumi , Hagiwara Kiyoshi , Nakajima Bun‐ichiro , Tokura Seiichi 
Published: April 2003

AbstractVarious kinds of sequential polypeptides were prepared by direct polymerization of peptides in the presence of diphenylphosphoryl azide (DPPA). Typically, polymerization reactions were carried out as follows; monomer peptide concentration: 300 mg/0,6 mL of DMSO (or some other solvent); amount of DPPA: 1,3 mol/mol peptide; amount of triethylamine: 2,3 mol/mol peptide (+1,0 mol/mol peptide in case of peptide hydrochloride); reaction time: 2 days at room temperature. Molecular weights of the resulting sequential polypeptides were estimated from their intrinsic viscosities in dichloroacetic acid and SDS‐polyacrylamide gel electrophoresis; they range from 4 000 to 30 000. The purity of the sequential polypeptides was confirmed by IR, elemental analysis and optical rotation measurements of their acid total hydrolysates.
Chiral liquid‐crystalline polymers by polymer‐analogous reactions
Authors: Kapitza Heinrich , Zentel Rudolf 
Published: April 2003

AbstractA synthetic route to combined main‐chain/side‐group chiral liquid‐crystalline (lc) polymers via precursor polymers with phenolic groups is presented. A polymer‐analogous reaction with chiral acids (conversions 90–100%) led to 33 new chiral lc polymers, which exhibit chiral smectic C*, smectic A, and cholesteric phases.
Copolymers and terpolymers of sulfur dioxide with allyl monomers comprising groups absorbing ultraviolet irradiation
Authors: Florjańczyk Zbigniew , Zygadło Ewa 
Published: April 2003

AbstractAlternating copolymers are obtained of sulfur dioxide with allyl phenyl ether, allyl p‐nitrophenyl ether, N‐allylbenzamide, N‐allyl p‐nitrobenzamide, allyl cinnamate and allyl o‐benzoylbenzoate. Copolymerizations proceed in high yield at ‐78°C in the presence of tert‐butyl hydroperoxide as initiator. However, copolymer yield is small for reactions initiated with 2,2′‐azoisobutyronitrile at 50–60°C. Ultraviolet spectra of the copolymers obtained show the presence of intense absorption bands in the range of 220 to 305 nm. SO2 terpolymers have been obtained with allyl ethers, allyl amides or allyl esters and 1‐heptene, 2‐methylpropene or methyl acrylate. The effect of the structure of the monomers on the reactivity in polymerizations involving SO2 is discussed on the basis of the composition of the products.
Etude de la dégradation thermique du poly{acétoxy‐1 [(chloro‐2 éthyl)‐4 phényl]‐1 éthylène}
Authors: Boinon Bernard , Brigui Jamal , Monthéard Jean‐Pierre 
Published: April 2003

AbstractA kinetic study of the thermal decomposition of poly{1‐acetoxy‐1‐[4‐(2‐chloroethyl)phenyl]‐ethylene} (1) was carried out by thermogravimetry. Two stages, well separated, are observed. The first one begins at 140°C. The corresponding decomposition reaction is a superposition of two reactions: loss of acetic acid and partial depolymerization. The main volatile products released in this first stage, identified by gas chromatography/mass spectrometry coupling, are chiefly acetic acid and a small quantity of p‐(2‐chloroethyl)acetophenone; there is no monomer from the monomeric unit. As in case of other poly(para‐substituted α‐acetoxystyrenes) the solid residue is poly[p‐(2‐chlorethyl)phenylacetylene] (5) of low molar mass, soluble in all usual organic solvents. No auto‐catalytic mechanism was found during this first stage, unlike in case of poly(vinyl acetate). The reaction order is one, over a wide range of conversion. The activation energy was found to be about 145,6 kJ/mol and the pre‐exponential factor 1,6 · 1015 min−1. An explanation for the insolubility of the residues, obtained by thermal degradation of some poly(p‐chloroalkylstyrenes), is proposed.
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 3. Telechelics containing indane units
Authors: Nuyken Oskar , Yang Dazhong , Gruber Freddy , Maier Gerhard 
Published: April 2003

AbstractThe synthesis and characterization of linear telechelics containing 1,1,3‐trimethylindane units via cationic polymerization is described. 1,4‐Diisopropenylbenzene (1) was polymerized in the presence of 1‐isopropenyl‐4‐methylbenzene (3a) to give a polyindane with methyl end‐groups, which was then oxidized to the corresponding carboxy‐telechelic polymer. As an alternative route for the preparation of polymers with indane units in the main chain, the step growth polymerization of suitably substituted indane derivatives was studied. In this way a polyindane with amino end‐groups was synthesized. It melts at 172°C and in DSC is stable up to ca. 300°C.