bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and deformation behaviour of model poly(ether‐urethane) elastomers, 1. Infrared studies
Authors: Reynolds Nicholas , Spiess Hans Wolfgang , Hayen Heidi , Nefzger Hartmut , Eisenbach Claus D. 
Published: April 2003

AbstractInfrared spectroscopy was used to study the structure and deformation behaviour of a series of model poly(ether‐urethane) (PEU) elastomers. These materials contain (molecularly) uniform hard segments obtained from piperazine and the bischloroformate of 1,4‐butanediol with a poly(oxytetramethylene) soft segment and contain no hydrogen bonding. Polarization infrared spectra were obtained simultaneously with stress‐strain measurements during deformation. The orientation of hard and soft segments was measured using static and oscillatory strain. The results are consistent with a lamellar hard‐domain structure in which lamellae orient in the stretching direction at low strain and are sheared apart at higher strains. The stress‐strain and orientation behaviours were found to be highly dependent on the thermal history with annealed samples showing a higher degree of hard‐segment order and resistance to strain‐induced disruption. The PEU samples show an initial rapid and a later gradual relaxation of stress and orientation which occur upon step strain as the hard domains, which are not stabilized by hydrogen bonding, are disrupted under strain. The carbonyl stretching vibration was found to be sensitive to the hard‐segment order. With increasing temperature or strain, an increase in a band component associated with a disordered structure was observed, along with a reduction of the hard‐segment orientation at high strain as the hard domains were disrupted. Under cyclic deformation at 1,6 Hz reversible hard‐segment orientation provides further evidence for lamellar rotation at small strains. Stress‐induced crystallization is observed near 300% strain.
Synthesis of poly(2,6‐dimethylphenylene sulfide) by photooxidative polymerization
Authors: Yamamoto Kimihisa , Oyaizu Kenichi , Tsuchida Eishun 
Published: April 2003

AbstractPhoto‐oxidation of bis(3,5‐dimethylphenyl) disulfide proceeds in the presence of aromatic nitriles as sensitizers. Catalytic amounts of 9,10‐dicyanoanthracene act as an electron mediator of the transfer from the disulfide to oxygen in the presence of biphenyl as a co‐sensitizer. The photo‐redox system enabled an efficient formation of poly(thio‐2,6‐dimethyl‐1,4‐phenylene) through electrophilic reaction of the sulfonium cation produced in the photo‐oxidation.
Graft copolymers from modified ethylene/vinyl acetate copolymers, 2. Synthesis of polystyrene‐grafted poly[ethylene‐co‐(vinyl acetate)] and evaluation of its compatibilizing effect in polystyrene/poly[ethylene‐co‐(vinyl acetate)] blends
Authors: Barbosa Ronilson V. , Soares Bluma G. , Gomes Ailton S. 
Published: April 2003

AbstractPolystyrene‐grafted poly[ethylene‐co‐(vinyl acetate)] (EVA‐g‐PS) has been synthesized from functionalized polystyrene containing acyl chloride end group (PS‐COCl) and partly (5%) hydrolyzed poly[ethylene‐co‐(vinyl acetate)] (EVALVA‐5%). The graft efficiency is ca. 100% when low‐molecular‐weight polystyrene is employed. By increasing the molecular weight of the grafts the efficiency decreases. These graft copolymers have been used for compatibilizing polystyrene (PS)/poly[ethylene‐co‐(vinyl acetate)] (EVA) blends. The ability of the copolymers as compatibilizing agent has been verified by an analysis of the mechanical properties and by scanning electron microscopy.
Raman spectroscopic study on water in aqueous solutions of temperature‐responsive polymers: Poly(N‐isopropylacrylamide) and poly[N‐(3‐ethoxypropyl)acrylamide]
Authors: Terada Takahiko , Inaba Taro , Kitano Hiromi , Maeda Yasushi , Tsukida Noriaki 
Published: April 2003

AbstractA Raman spectroscopic study on property changes of water in the course of a temperatureresponsive solution‐aggregate transition phenomenon of aqueous poly(N‐isopropylacrylamide) and poly[N‐(3‐ethoxypropyl)acrylamide] solutions was carried out. Upon the transition of polymers from coil to globule followed by the aggregation of individual polymer chains, the height ratio of the the peaks at 3250 and 3 400 cm−1, corresponding to the OH stretching of water molecules, was drastically changed. Contribution of small water domains included in polymer aggregates (so‐called interstitial water) to the change in the Raman spectra was suggested. Effects of polymer concentration and molecular weight of polymers on the spectra were also examined.
1H and 13C NMR determination of the hydroxy end‐groups in poly(oxypropylene)s
Authors: Kříž Jaroslav , Stehlíček Jaroslav 
Published: April 2003

Abstract1H and 13C NMR signals of tri(propylene glycol) and of its benzoate and phenyl urethane were assigned by means of 1D and 2D NMR methods such as super‐selective long‐range INEPT, H‐H COSY, H‐C COSY and H‐H‐C RCT spectra. Both 1H and 13C NMR were used as methods for the determination of primary and secondary hydroxy end‐groups and of their degree of conversion. 13C NMR was found to be a reliable and universal method of end‐group determination even for cases where 1H NMR fails due to the presence of water in the sample or to the nature of the reactant. The results are applied to the analysis of poly(oxypropylene)s with two or three hydroxy end‐groups and their derivatives.
Hydroxytelechelic polybutadiene, 13. Microstructure, hydroxyl functionality and mechanisms of the radical polymerization of butadiene by H2O2
Authors: Poletto Sylvie , Pham Quang Tho 
Published: April 2003

AbstractThe mechanism of the radical polymerization of butadiene with H2O2 has been clarified by indepth examination of very low M̄n hydroxytelechelic polybutadiene (HTPB) synthesized with high concentration of H2O2. For the well‐known R45M®‐HTPB1,2, only primary alcohol functions were found, and most of them originate from initiation steps (termination mechanisms only proceed by coupling of macroradicals); in low M̄n HTPB (HTPB‐C), the presence of a secondary alcohol function suggests termination reactions by coupling between macroradicals and primary hydroxyl radicals. Being more branched, HTPB‐C has a larger hydroxyl content, and also a larger amount of epoxidized 1,4‐units. Finally, some lower alcohols, utilized for homogenizing H2O2 with butadiene, are also transfer agents giving rise to ether groups.
Hydrosilylation of 1‐alkenes with dichlorosilane
Authors: Out Gerardus J. J. , Klok Harm‐Anton , Schwegler Leonore , Frey Holger , Möller Martin 
Published: April 2003

AbstractSymmetrically and unsymmetrically substituted diorganodichlorosilanes have been prepared by hydrosilylation with dichlorosilane using two different platinum catalysts, i.e., hexachloroplatinic acid (“Speier's catalyst”) and a platinum cyclovinylmethylsiloxane complex. Hydrosilylation of unsubstituted 1‐alkenes proved to be very efficient, yielding anti‐Markonikov substituted di‐n‐alkyldichlorosilanes. However, no reaction was observed when electron‐deficient 1‐alkenes were used. Octacarbonyldicobalt enabled formation of the monoadduct of 1H,1H,2H‐perfluoro‐1‐hexene with dichlorosilane, which was employed in a second hydrosilylation of the olefin. Thus, the anti‐Markovnikov diadduct was obtained in 40% overall yield. The two‐step synthesis has also been applied successfully to obtain unsymmetrically substituted diorganodichlorosilanes containing nitrile and ether groups.
Electrooptically active polymers, 2. Influence of chromophore structure on thermal properties
Authors: Ahlheim Markus , Lehr Friedrich 
Published: April 2003

AbstractA series of novel diazo dye containing nonlinear optical (NLO) polymers and model compounds are prepared and the influence of the chromophore length on polymer‐specific behavior such as solubility, glass transition temperature and decomposition temperature is described.
Kinetics of the chemical polymerization of pyrrole by potassium hexacyanoferrate(III)
Authors: Stanković Rade , Laninović Verica , Stanković Slavka , Jovanović Slobodan , Vojnović Milan 
Published: April 2003

AbstractThe kinetics of the chemical polymerization of pyrrole by potassium hexacyanoferrate(III) in water at 0°C was studied. The order of the reaction with respect to both pyrrole and potassium hexacyanoferrate(III) was determined to be 1 and 2,6, respectively. The rate constant k of the polymerization reaction was found to be 2,25 · 10−4 (dm3 · mol−1)2,6 · s−1.
Microheterogeneities of core‐shell latexes probed by 1H spin diffusion and transmission electron microscopy
Authors: Spiegel Stefan , Landfester Katharina , Lieser Günter , Boeffel Christine , Spiess Hans Wolfgang , Eidam Norbert 
Published: April 2003

AbstractA core‐shell latex built up of polybutadiene as a mobile component and polystyrene as a rigid component is investigated. Solid‐state NMR spectroscopy and transmission electron microscopy are used to characterize the morphology and possible heterogeneities of the latex particles (average particles sizes 70–100 nm). NMR spectroscopy allows the determination of average domain distances much below the particle size due to standard electron microscopy. These differences are explained by an additional microstructure of the core‐shell particles. Indeed, electron micrographs at high resolution confirm the existence of heterogeneities within the polybutadiene core of the latex. The presented investigations demonstrate the power of a combined application of solid‐state NMR spectroscopy and transmission electron microscopy for the characterization of core‐shell latexes.
Synthesis and crosslinking of new bis(4,5‐epoxytetrahydrophthalimides)
Authors: Monte Dámaso , Galià Marina , Cádiz Virginia , Mantecón Ana , Serra Angels 
Published: April 2003

AbstractPreparation and characterization of novel cycloaliphatic epoxy resins derived from tetrahydrophthalimide compounds were studied. Crosslinking studies on these resins were carried out using differential scanning calorimetry (DSC) and thermal gravimetry analysis (TGA). Thermal crosslinking overlaps with degradation and, therefore, hardeners or catalysts were used in order to decrease the crosslinking temperature. Primary or tertiary amines did not give curing reaction but the latter afforded isomerization to produce phthalimides when the amine was used in a great proportion. On the other hand, the use of anhydride (cis‐1,2‐cyclohexanedicarboxylic anhydride) as hardener and a tertiary amine (4‐dimethylaminopyridine) as accelerator led to crosslinked materials. DSC was used to follow the reaction and a dynamic method was applied to obtain kinetic parameters. Thermal stability was evaluated by TGA.
Morphology control of a MgCl2‐supported Ziegler‐Natta catalyst by the recrystallization method
Authors: Chung Jin Suk , Song In Kyu , Lee Wha Young , Park Hong Man 
Published: April 2003

AbstractMgCl2 supports were prepared by the recrystallization method with variation of agitation speed and MgCl2 concentration of the MgCl2‐methanol‐decane mixture. It was found that the particle size of MgCl2 and MgCl2/TiCl4 could be controlled by changing the MgCl2 concentration in a methanol droplet or by changing the size of the methanol droplets. The particle size of the supports and catalysts increased with decreasing speed of agitation and with increasing MgCl2 content. All the prepared supports and catalysts showed a good spherical morphology.
Synthesis of polypropene‐graft‐poly(ε‐caprolactone)
Authors: Zhang Qi‐jin , Wen Jun , Luo Xiao‐lie , Wang Zhi‐yong 
Published: April 2003

AbstractThe copolymerization of polypropene (PP) with maleic anhydride (MA) was carried out at 120°C in xylene with benzoyl peroxide (BPO) as initiator. The resulting product was identified as poly(propene‐co‐maleic anhydride) obtained by reaction of the double bond of maleic anhydride with free radicals created on the PP chain. In the next step this copolymer was reacted with functional poly(ε‐caprolactone) (PCL) by a co‐melting method to give rise to a graft copolymer. The optimum time for the second step was found to be around 6 h (at 120°C). X‐ray diffraction measurements and DSC characterization of PP‐g‐PCL have shown that the melting point of the PP phase in the graft copolymers is lower than that of homopolypropene and that its glass transition temperature increases with increasing of PCL grafts.
Self‐assembly of the electroactive complexes of polyaniline and surfactant
Authors: Zheng Wen‐Yue , Wang Rong‐Hai , Levon Kalle , Rong Zhao Y. , Taka Tapani , Pan Wendy 
Published: April 2003

AbstractAn electroactive material with remarkable solubility, processibility as well as mechanical properties has been developed by complexation (thermal doping) of polyaniline (PANi) emeraldine base with dodecylbenzenesulfonic acid (DBSA) in the solid state. Isothermal treatment of such a mixture was found to promote the complex formation. Optimum conditions of complexation were established with respect to the formation of layered structure, electrical conductivity and solubility. The optimal temperature for the doping process was found to be in a range of 100–120°C while the best ratio of DBSA to PANi was between 3:1 and 4:1 by weight, a nearly stoichiometric equivalence of aniline repeat units and DBSA molecules. The time of isothermal treatment should be controlled within 30 min. Thermal doping induced orientation to polymer chains in a layered structure, whereby the hydrophobic tails of the surfactants function as spacers between parallel stacks of the main chains. This anisotropy was achieved by the self‐assembly during the thermal doping rather than ordinary drawing or stretching of the polymers. A unique liquid crystalline mesophase with a smectic‐like optical texture was observed for the soluble portions of some specimens. The excess DBSA in the samples is considered to function as a solvent and to give rise to the liquid crystalline fluidity of the phase. The scanning tunneling microscopy (STM) image 5000 × 5000 Å on a submicrometer scale obtained from a PANi/DBSA thin film exhibits a surface morphology with a granular size of 200–300 Å. The image of 150 × 150 Å on a molecular scale obtained from multilayer PANi/DBSA deposited on a highly oriented pyrolytic graphite (HOPG) surface provides a direct observation of a self‐assembled structure and close layer packing of the polymer backbone with dimensions in accord with the results found by X‐ray diffraction. Our results indicate that the thermal doping process of polyaniline by DBSA offers new possibilities to obtain optimal structures through a self‐assembly.
An electron spin resonance study of poly(α‐ethynylnaphthalene) polymerized with [Rh(norbornadiene)Cl]2 and WCl6 as catalysts
Authors: Tabata Masayoshi , Yokota Kazuaki , Namioka Makoto 
Published: April 2003

AbstractPoly(α‐ethynylnaphthalene)s (PENAPs) obtained with the Rh complex [Rh(norbornadiene)Cl]2 as a stereoregular polymerization catalyst of monosubstituted acetylene monomers and WCl6 were studied by using the electron spin resonance (ESR) method to inspect the geometrical structure with respect to the CC bond in the main chain where π‐radicals called solitons may be stabilized in the conjugated polymer chain. In PENAP obtained as the immobile unpaired electrons were found to be stabilized in the polymer chain, indicating a short and restricted conjugated chain, i. e., formation of a cis‐transoid polymer. In PENAP obtained with WCl6 as catalyst more mobile unpaired electrons were found to be stabilized in the conjugated polymer chain not only at room temperature but also at lower temperature, indicating the presence of a π‐conjugated main chain, i. e. of a trans‐transoid polymer. Moreover it was found, interstingly, that the clearly resolved ESR spectrum with the hyperfine structure (solitin) could be observed at higher temperature, i. e., ca. 300°C.
Critically evaluated rate coefficients for free‐radical polymerization, 1. Propagation rate coefficient for styrene
Authors: Buback Michael , Gilbert Robert G. , Hutchinson Robin A. , Klumperman Bert , Kuchta Frank‐Dieter , Manders Bart G. , O'Driscoll Kenneth F. , Russell Gregory T. , Schweer Johannes 
Published: April 2003

AbstractPulsed‐laser polymerization (PLP) in conjugation with molecular weight distribution (MWD) measurement has emerged as the method of choice for determining the propagation rate coefficient kp in free‐radical polymerizations. Detailed guidelines for using this technique (including essential internal consistency checks) and reporting the results therefrom are given by the authors, members of the IUPAC Working Party on Modeling of kinetics and processes of polymerization. The results for PLP‐MWD kp measurements from many laboratories for bulk free‐radical polymerization of styrene at low conversions and ambient pressure are collated, and are in excellent agreement. They are therefore recommended as constituting a benchmark data set, one that is best fitted by

(the confidence ellipsoid for the Arrhenius parameters is also given). These benchmark data are also used to evaluate the merits of several other methods for determining kp; it is found that appropriately calibrated electron paramagnetic resonance spectroscopy appears to yield reliable values of kp for styrene.
Poly(oxyethylene)s terminated at both ends with phosphonium ion end groups, 2. Properties
Authors: Kubisa Przemysław , Biedroń Tadeusz 
Published: April 2003

AbstractPoly(oxyethylene)s with number‐average degrees of polymerization (DPn) ranging from ≈ 6 to ≈ 80, terminated at both ends with phosphonium ion end groups (diionic poly‐EO), have been prepared and characterized as described in the preceding paper. Viscosities of diionic poly‐EO were measured, both in solution and in bulk. In chloroform solution, at low concentration (< 1 g/100 mL), the viscosity of diionic poly‐EO was lower than the viscosity of nonionic (terminated with HO‐groups) poly‐EO of the same DPn. At higher concentrations, the viscosity of diionic poly‐EO exceeded that of nonionic poly‐EO and increased sharply with increasing concentration. At the constant weight concentration of ≈4 g/100 mL, the viscosities of short‐chain diionic poly‐EO were higher and those of longer chain diionic poly‐EO were lower than the viscosities of the nonionic poly‐EO of the same chain lengths. These results were attributed to a predominant intramolecular aggregation of terminal ionic groups at low concentration of ionic groups in solution and predominant intermolecular aggregation at higher concentration of ionic groups. The results of bulk viscosity measurements as well as the results of differential scanning calorimetry measurements of the dependence of the glass transition temperature on the DPn of diionic poly‐EO indicated that in bulk physically cross‐linked networks were formed, due to intermolecular aggregation of terminal ionic groups.
Linear non‐conjugated dienes from biomass as termonomers in EPDM synthesis, 2. Comparison with 5‐ethylidene‐2‐norbornene termonomer
Authors: Dolatkhani Marc , Cramail Henri , Deffieux Alain 
Published: April 2003

AbstractA comparative study of 5‐ethylidene‐2‐norbornene (ENB) or 5,7‐dimethylocta‐1,6‐diene (5,7‐DMO) as diene termonomer in ethylene‐propylene‐diene (EPDM) terpolymer synthesis is presented. The reactivities of the cyclic and linear non‐conjugated dienes are first compared in homopolymerization in the presence of two conventional Ziegler‐Natta catalytic systems: TiCl3, 1/3AlCl3, 14MgCl2 associated to AlEt3, and VOCl3 (or VCl4) associated to AlEt2Cl. ENB polymerization yields a branched poly(ENB) in agreement with a predominant cationic reaction, whereas polymerization of 5,7‐DMO proceeds exclusively by a Ziegler‐Natta mechanism. In terpolymerization, ENB is much more reactive than 5,7‐DMO and is incorporated more easily in the terpolymer. However, the high sensitivity of ENB toward acidic species also results in cationic side reactions and therefore limits the utilization of ENB to a low concentration range. We have shown that the productivity of vanadium catalysts, which are mainly used in industrial EPDM synthesis, is drastically reduced in the presence of ENB an 5,7‐DMO, due to the rapid reduction of vanadium involving the diene.
Photocrosslinkable copolymers of 4‐vinylbenzyl selenocyanate, 4‐vinylbenzyl thiocyanate and 4‐vinylbenzyl bromide: Experiments with low‐molecular‐weight model compounds
Authors: Kern Wolfgang , Saf Robert , Hummel Klaus , Kapeller Herwig 
Published: April 2003

AbstractThe photocrosslinking mechanism of copolymers of styrene (ST) with 4‐vinylbenzyl selenocyanate (VBSe), 4‐vinylbenzyl thiocyanate (VBT) or 4‐vinylbenzyl bromide (VBBr) was investigated using low‐molecular‐weight model compounds. The photochemistry of benzyl selenocyanate was studied by means of 1H NMR spectroscopy and gas chromatography/mass spectrometry (GC/MS) analysis. It was found that a cleavage in benzyl and selenocyanato radicals and — to a minor extent — in benzylseleno and cyano radicals occurs. A comparative study of the products which are formed during the photolysis of benzyl selenocyanate, benzyl thiocyanate and benzyl bromide in cumene shows that selenocyanato and thiocyanato radicals have far less hydrogen abstraction efficiency than bromine radicals. The results are discussed in regard to the reactions of the corresponding copolymers. A comparison with a crosslinking mechanism, proposed for chloromethylated polystyrene under irradiation, is carried out.
Synthesis of amorphous poly(thioarylene)s via oxidative polymerization of diaryl disulfides
Authors: Miyatake Kenji , Jikei Mitsutoshi , Yamamoto Kimihisa , Tsuchida Eishun 
Published: April 2003

AbstractAmorphous poly(thioarylene)s containing a methyl substituent and/or an ether bond in the main chain were prepared via oxidative polymerization of diaryl disulfides using 2,3‐dichloro‐5,6‐dicyanobenzoquinone. The resulting poly(thio‐2,6‐dimethyl‐1,4‐phenyleneoxy‐1,4‐phenylene) having alternating ether and thioether bonds shows a better solvent solubility and has a higher glass transition temperature (Tg) (182°C) than non‐substituted poly(thio‐1,4‐phenylene). Polymerization of methyl substituted diphenyl ether derivatives with disulfur dichloride has been also developed for a one‐pot synthesis of amorphous poly(thioarylene)s.
Thermotropic polyesters, 9. Liquid crystalline polyesters with fluorinated spacers
Authors: Bilibin Alexander Yu. , Sokolova Olga S. , Grigorjev Anatoly J. 
Published: April 2003

AbstractTwo series of fluorine‐containing liquid crystalline polyesters were synthesized from fluorinated alkylene diols and mesogenic acid dichlorides. The thermal behaviour of the polymers differs considerably from that of their hydrocarbon analogues. Formation of a nematic phase was observed only for melts of polymers with fluorinated spacers whereas polymers with alkylene spacers form mainly smectic phases. The most interesting feature is the unusual dependence of the polymer melting temperature on the spacer length — it increases with increasing number of CF2 groups in the spacer.
Towards the propagation rate coefficient for the free‐radical polymerization of 1,3‐butadiene
Authors: Bandermann Friedhelm , Günther Claus , Schweer Johannes 
Published: April 2003

AbstractThe propagation rate coefficient kp for the free‐radical polymerization of 1,3‐butadiene was determined as a function of temperature in the range of 30–60°C in bulk and as a function of the concentration of 1,3‐butadiene in chlorobenzene at 50°C using a combination of a UV flash‐lamp induced polymerization and a measurement of the molecular weight distribution of the produced polymer by size exclusion chromamgraphy. Differences of up to around 45% resulted even for the same concentrations and temperatures when these measurements were compared with recent determinations of kp of 1,3‐butadiene in chlorobenzene in which just such an experimental setup was used. This finding was essentially attributed to large differences in the radical termination rates which prevailed in the reaction volumes under the current conditions of the pulse‐induced polymerization experiments. Moreover, in the vicinity of bulk concentrations of 1,3‐butadiene in chlorobenzene, kp apparently decreases with concentration.