bluuebunny/crossref_metadata_2025 huggingface dataset:
Living cationic polymerization of cyclohexyl vinyl ether
Authors: Cramail Henri , Deffieux Alain
Published: April 2003

The cationic polymerization of cyclohexyl vinyl ether (CHVE) initiated by α‐halogeno ethers in the presence of a Lewis acid activator has been investigated first. In conditions leading to a living polymerization of alkyl vinyl ethers (ethyl, isobutyl, etc.), an extremely fast polymerization, accompanied by chain transfer reactions, is observed with CHVE. In fact, we have shown that the polymerization of this monomer may be directly initiated by the HI and HCl adducts of CHVE, in the absence of any electrophilic activator. However, even in these conditions, the polymerization cannot be controlled. A “living” polymerization of CHVE was finally obtained by addition of ammonium salts (NBu4X; X = Cl, Br, I) to the systems free of electrophilic activators. The added salts stabilize the α‐halogeno ether chain ends and reduce the overall reactivity. Using this procedure, we have synthesized poly(CHVE)s with M̄n's ranging from 6 · 103 to 4 · 104 g · mol−1 (in good agreement with the predicted values assuming the formation of one polymer chain per initiator molecule) and narrow molecular weight distributions (M̄w/M̄n < 1,2). Though most of poly(alkyl vinyl ether)s exhibit glass transition temperatures far below 0°C, the glass transition temperature of the poly(CHVE) is close to +50°C, indicating that this monomer can be used as a precursor to rigid poly(vinyl ether) blocks.
Free radical synthesis of α,ω‐primary amino functionalized polyisoprene through the functional thermal inferter [bis(N‐(2‐phthalimidoethyl)piperazine)]thiuram disulfide
Authors: Clouet Gilbert , Juhl Hans Jürgen
Published: April 2003

The primary amino functional iniferter [bis(N(2‐phthalimidoethyl)piperazine)]thiuram disulfide (PEPTD) was synthesied and characterized. Thermal polymerization of isoprene in the presence of the initiator afforded α,ω‐functionalized polyisoprene with primary amino end‐groups after cleavage of the phthalimido group with butylamine. The kinetics of polymerization of isoprene using this iniferter was studied at 80, 85, 90 and 100°C. Interestingly, isoprene showed a complex kinetic behavior. The different parameters, related to initiation, chain transfer and primary radical termination reactions, as well as the constants for thermal decomposition of the initiator, were determined. From the Arrhenius plot, the activation energy of the overall decomposition constant of PEPTD (2 f kd) was calculated to be 110 kJ/mol. The functionality of the telechelics was examined by GPC.
Polymorphism of poly[bis(p‐methoxyphenoxy)phosphazene]
Authors: Miyata Tadakazu , Masuko Toru , Kojima Morio , Magill Joseph H.
Published: April 2003

Well characterized poly[bis(p‐methoxyphenoxy)phosphazene] (PB(4‐MeO)PP) has been investigated employing X‐ray diffraction and differential scanning calorimetry (DSC). The DSC heating scan of the original PB(4‐MeO)PP specimen exhibits one exotherm at 110°C and two endotherms at 106°C and 126°C, respectively. Only a single endotherm at 131°C appears on the second heating. X‐ray diffraction measurements at elevated temperature reveal that PB(4‐MeO)PP crystal is monoclinic (β‐form) with unit cell dimensions a = 2,47 nm, b = 1,98 nm, c = 0,983 nm and y = 102° in the range of 106–126°C. Initially PB(4‐MeO)PP specimens are observed to be orthorhombic (α‐form) with a = 2,39 nm, b = 1,79 nm and c = 0,983 nm. The crystal transforms at 106°C and then changes into the β‐form at 110°C according to DSC measurements. At 126°C the β‐form crystal changes into a mesophase with an intermolecular distance of 1,44 nm at 150°C. The 3‐dimensional orthorhombic γ‐form with a = 2,21 nm, b = 2,01 nm and c = 0,963 nm is found at room temperature after specimens are cooled through T(1) = 126°C from the mesophase.
Carbon 13 NMR study of oligo(propylene oxide)s
Authors: Le Borgne Alain , Moreau Michel , Vincens Valérie
Published: April 2003

Samples of dimer and trimer derived from chiral propylene oxide, having head‐to‐tail linkages were prepared using an aluminium complex of a Schiff's base and were studied by means of 13C NMR spectroscopy. Based on these spectroscopic data and on J‐Modulated Spin Echo Technique (JMSET), analysis of a racemic oligomer (DPn ≈ 11) was carried out. Resonances of carbon atoms of central and terminal units were identified. End‐group carbon atoms (with the exception of CH2Cl) present large configurational effects as compared to internal carbon atoms.
Modeling of termination in intermediate and high conversion free radical polymerizations
Authors: Buback Michael , Huckestein Brigitta , Russell Gregory T.
Published: April 2003

A simple means of modeling termination in free radical polymerizations of a large number of monomers over a wide variety of intermediate and high conversion conditions is presented. It is shown that monomers can be divided into two classes according to the qualitative variation of their termination rate coefficient (kt) with conversion (U). It is then suggested that it is profitable to represent kt data as kt/[kp·(1 − U)]. Doing this reveals that over a wide range of temperatures and of intermediate and high conversions, seemingly complex variations of kt with U can be described by a single parameter (CRD), the value of which varies from monomer to monomer. Proceeding from the idea that the process of reaction‐diffusion is the rate determining mechanism of termination, two easily implementable models for a priori prediction of CRD are developed in parallel from already existing ideas. One of these models is shown to predict with remarkable accuracy a large variety of experimental CRD data. Slight modification of these predictions makes this model even more accurate, and therefore gives it great potential for modeling purposes.
Block copolymers of poly(ether‐ether‐sulfones) with liquid‐crystalline/non‐liquid‐crystalline polyesters
Authors: Brenda Silviz , Heitz Walter , Karback Alexander , Wehrmann Rolf
Published: April 2003

The synthesis of telechellcs of poly(ether‐ether‐sulfones) (PEES) is controlled by high‐resolution gel‐permeation chromatography to optimize for low content of side products. Under optimum conditions the bifunctional polymer‐homologous series is formed to 99,9%. These telechrcs were used to synthesize block copolymers with aromatic polyesters. The polyesters (PE) contain phenylhdroquinone and terephthalic acid (semicrystalline liquid‐crystalline (LC) polyester), phenylterephthalic acid (amorphous LC polyester) or isophthalic acid (amorphous non‐LC polyester). Block copolymers with amorphous polyesters show one glass transition temperature depending on the composition but blends of corresponding homopolymers are biphase. Block copolymers with semicrystalline LC polyesters are phase‐separated. Incorporation of semicrystalline LC polyester segments into PEES increases their solvent resistance. The storage modulus of the block copolymer with 50 wt.‐% of the semicrystalline polyester shows the same temperature dependence as PEES. Homogeneous block copolymers show anisotropy only if the weight fraction of polyester is larger than 0,5 whereas phase‐separated systems show anisotropy at smaller fractions of polyester.
Synthesis of star‐shaped polydimethylsiloxanes containing SiO2 core units
Authors: Ogawa Takuya , Suzuki Toshio , Mita Itaru
Published: April 2003

Star‐shaped polysiloxanes consisting of SiO2 cores and polydimethylsiloxane (PDMS) branches were successfully prepared by three methods using functionalized solvent‐soluble silicates as a starting material. The first method involved the lithiation of a SiOH functional silicate with butyllithium, followed by reaction with hexamethylcyclotrisiloxane (D3) and termination with a chlorosilane to afford a star polymer. In this case, the chain ends were substituted with vinyl or SiOH functional groups. In the second method, a SiCl functional silicate was used as the source of the SiO2 core. A PDMS chain with a lithium silanolate terminal group was reacted with the SiCl functional silicate to provide a star polymer. In the third method, a PDMS chain with a diethylamino group at one chain end was reacted with the SiOH functional silicate to form a star polymer. The Mark‐Houwink constant a of the star polymer was 0,74, which is very close to that of a linear PDMS.
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

Infrared 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

Photo‐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

Polystyrene‐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

A 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

1H 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

The 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

Symmetrically 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

A 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

The 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

A 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

Preparation 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

MgCl2 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

The 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

An 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

Poly(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

Pulsed‐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

Poly(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

A 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

The 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

Amorphous 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

Two 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

The 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.
Negative pressure effects during the isothermal crystallization of isotactic poly(propylene) studied by light and atomic force microscopy
Authors: Thomann Ralf , Wang Chun , Kressler Jörg , Mülhaupt Rolf
Published: April 2003

The formation of holes during the late stage of the isothermal crystallization in thin films of isotactic poly(propylene) between two cover glasses was observed by light microscopy and atomic force microscopy. This behavior can be described consistently by the well‐known negative pressure effect. Light microscopy reveals the simultaneous and sudden occurrence of a large number of small holes at the liquid‐solid interface after the liquid in front of the spherulites is completely confined by other spherulites for a certain time interval. In exceptional cases only a few holes appear and finally large cavities are formed. Atomic force microscopy measurements carried out in the height mode are able to prove the hole formation in front of the spherulites. Furthermore, a substantial thinning of the two‐dimensional spherulites in thin films can be observed prior to the hole formation.
Kinetic study of free‐radical copolymerization of methyl acrylate and methyl methacrylate in benzene
Authors: Madruga Enrique López , Fernández‐García Marta
Published: April 2003

The variation of copolymerization rate with composition obtained for the system methyl acrylate (1)/methyl methacrylate (2)/benzene/2,2′‐azoisobutyronitrile using standard techniques of polymerization rate measurements has been interpreted on the basis of a penultimate effect upon the propagation reaction, giving values of s1 = 0.547 and s2 = 1.668 for the chain‐end reactivity ratios.
Mechanical and thermal behaviour of networks with “flexible” and “rigid” chains
Authors: Müller Andrea , Stadler Reimund
Published: April 2003

“Rigid‐rod” telechelics were synthesized via repetitive Diels‐Alder reaction of biscyclohexadienes and bis(1,2,4‐triazoline‐3,5‐diones). The bistriazolinediones were used in slight excess. The rigidity of the building blocks and the molecular weight were varied. Various amounts of these reactive telechelics are used to crosslink cis‐1,4‐polybutadiene. The mechanical and the thermal properties of these two‐component networks were investigated by stress‐strain, differential scanning calorimetry and dynamic‐mechanical measurements. The occurrence of microphase separation between the “rigid” and the “flexible” components is discussed to explain the properties of these materials.
Telechelic diols from poly[(R)‐3‐hydroxybutyric acid] and poly{[(R)‐3‐hydroxybutyric acid]‐co‐[(R)‐3‐hydroxyvaleric acid]}
Authors: Hirt Thomas D. , Neuenschwander Peter , Suter Ulrich W.
Published: April 2003

We describe the preparation of telechelic OH‐terminated poly[(R)‐3‐hydroxybutyric acid] (PHB) and poly{[(R)‐3‐hydroxybutyric acid]‐co‐[(R)‐3‐hydroxyvaleric acid]} (PHB/HV), on a semi‐preparative scale, by a transesterification procedure from the high‐molecular weight polymers. The oligomers have well‐defined reactive end groups and are well suited for the preparation of high‐molecular‐weight block copolymers by chain extension.
Supported catalysts for ethylene polymerization: studies with the magnesium diethoxide‐tin tetrachloride‐titanium tetrachloride/tetraisobutylalumoxane catalyst system
Authors: Gupta Virendra K. , Ravindranathan Marayil
Published: April 2003

Supported titanium catalysts are prepared by the reaction of magnesium diethoxide with tin tetrachloride followed by treatment with titanium tetrachloride. The catalysts are characterized by compositional analysis and measurements of the specific surface area. The performance of the catalysts is evaluated for the polymerization of ethylene using tetraisobutylalumoxane as cocatalyst. The rate of polymerization decreases with increasing reaction time indicating a decay‐type kinetic profile. Catalyst composition and concentration of cocatalyst govern the performance of the system.
Determination of the optical anisotropy of atactic polystyrene using a grating monochromator
Authors: da Silveira Nádya Pesce , Samios Dimitrios , Strehle Frank , Dorfmüller Thomas
Published: April 2003

To extract the intrinsic molecular scattering from unwanted collision‐induced contributions as much as possible we propose a simple useful method recording the depolarized Rayleigh spectra using a double grating monochromator and correcting the spectra for the high‐frequency wings. For this purpose we tested the system polystyrene/CCl4 for which an asymptotic value of the optical anisotropy 〈γ2〉/x ≅ 30 Å6 with degree of polymerization x > 20 was found. The depolarized Rayleigh intensity of 2,4‐diphenylpentane and anionically polymerized atactic polystyrene standards was also measured in dilute solutions in the θ‐solvent bicyclohexyl (θ = 61°C). From the absolute depolarized Rayleigh ratio we obtained the configurational average optical anisotropy per number of monomer units, 〈γ2〉/x. We have chosen cumene as a model compound estimating that its optical anisotropy is similar to that of a quasi monomer unit. No significant temperature dependence of 〈γ2〉/x and of the static internal pair correlation in the temperature range from 25°C up to 80°C was found.
Side‐chain liquid crystal polymers of 2,3‐disubstituted norbornenes via ring‐opening metathesis polymerization, 2. Methoxybiphenyl as mesogenic group, influence of flexible spacer length m = 4 to 10 on the thermotropic behaviour
Authors: Winkler Berthold , Ungerank Markus , Stelzer Franz
Published: April 2003

We report the synthesis and ring‐opening metathesis polymerization of (±)‐exo,endo‐bis[ω‐(4′‐methoxybiphenyl‐4‐yloxy)alkyl] bicyclo[2.2.1]‐hept‐5‐ene‐2,3‐dicarboxylates using the molybdenum‐carben initiator Mo(CH‐t‐Bu)(NAr)(OCCH3)(CF3)(2)2 with NAr = 2,6‐diisopropylaniline. The spacer length was varied from m = 4 to 10 methylene groups. All monomers and polymers show mesophases of the smectic type. Independently of the spacer length no glass transition was detected. An odd‐even effect of transition temperatures was observed for both the monomers and polymers. The monomers with m > 5 showed more phase transitions in the DSC‐heating runs. Dependency of liquid crystalline transition temperatures on molecular weight is shown for one polymer (m = 6). Transition temperatures are roughly constant for polymers consisting of more than 30 repeating units. In contrast, the enthalpy changes of these transitions are nearly independent of the molecular weights once the polymers contain more than 10 repeating units, but they are strongly dependent on spacer length, with a minimum at m = 6.
Thermosets obtained by chemical modification of poly(epichlorohydrin) with vinyl‐terminated aromatic carboxylates
Authors: Reina Jose Antonio , Serra Angels , Cádiz Virginia
Published: April 2003

Poly(epichlorohydrin) was modified in a high extent with several vinyl‐terminated aromatic potassium carboxylates (4‐(2‐propenyloxy)benzoate, 4‐(5‐hexenyloxy)benzoate, 3‐(2‐propenyloxy)‐2‐naphthoate, 3‐(5‐hexenyloxy)‐2‐naphthoate and 2‐(thioallyl)nicotinate) under solid‐liquid phase‐transfer conditions. Simultaneously with this substitution reaction, cleavage and crosslinking side reactions occurred. The polymers obtained were characterized by NMR, IR, elemental analysis, viscosimetry, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Then, crosslinked materials were obtained by curing mixtures of these linear polymers with 10% w/w of a radical initiator (dicumyl peroxide or 2,2′‐azoisobutyronitrile) on a DSC device. Finally, the thermal stability of the thermosetting materials was tested by TGA, and the Arrhenius kinetic parameters were determined for dicumyl peroxide initiated crosslinking processes by calorimetric measurements.
Polymers made from cholic acid derivatives: selected properties
Authors: Zhang Y. H. , Zhu X. X.
Published: April 2003

Polymers of methacrylate and methacrylamide derivatives of cholic acid were prepared by free radical polymerization in solution. To verify the stereoisomeric effect of the monomeric units, certain properties of the resulting polymers were compared, including conversion rate, molecular weight, and glass transition temperature. The 3β‐epimers of the methacrylates and methacrylamides are to polymerize more easily than the 3α‐epimers. Water absorption experiments showed that the methacrylamide polymers are more hydrophilic than the methacrylate polymers and that the polymers from the 3β‐epimers have higher hydrophilicity than those made from the 3α‐epimers. The free acid forms of the polymers were also prepared by selective hydrolysis of the methyl ester group of the cholic acid moiety which resulted in improved hydrophilicity of the polymers.
Fixation of pharmacologically active amines on polyphosphonates, 3. Synthesis and preliminary in vitro cytotoxic studies of bis(2‐chloroethyl)amino group containing polyphosphonates
Authors: Fontaine Laurent , Marbœuf Céline , Brosse Jean‐Claude , Maingault Martine , Dehaut Frédéric
Published: April 2003

Hydrosoluble poly(3,6,9‐trioxaundecamethylene phosphonate) with attached cytotoxic bis(2‐chloroethyl)amine in the side chain was synthesized by chemical modification of the corresponding polyphosphonate via the Atherton‐Todd reaction. The structure of the product was confirmed by 1H, 13C and 31P NMR spectroscopy. Preliminary in vitro cytotoxic studies revealed that the polymeric derivative exhibited an eight fold more cytotoxic potency against human hepatocellular carcinoma cell line HepG2 than against murine leukemia cell line L1210.
Interpolymer complexes of a graft copolymer with polyelectrolytes and equivalent blends of binary homopolymer complexes: A comparative study of their stability and thermodynamic parameters
Authors: Chatterjee S. K. , Misra Neeti
Published: April 2003

Interpolymer complexes of acrylamide/vinyl alcohol graft copolymers (AAm/VA) were prepared with two typical polyelectrolytes, e. g. poly(methacrylic acid) (PMA) and poly(ethyleneimine) (PEI). The equivalent blends of the same composition as the graft copolymer complexes were also prepared by mixing stoichiometric portions of binary homopolymer complexes. The stability constant (K), degree of linkage (θ) and related thermodynamic parameters (e. g. standard free energy change ΔG0, standard enthalpy change ΔH0 and standard entropy change ΔS0) were determined for each system by using Osada's method. The comparative study between graft copolymer complexes and equivalent blends indicated a considerable difference in these parameters. An interpretation of this discrepancy was sought in terms of copolymer effect, neighbouring group influence, and the nature of secondary binding forces upon interpolymer complexation.
Polymerization of cyclotrisiloxanes by organolithium compounds and P2‐Et base
Authors: Molenberg Aart , Möller Martin
Published: April 2003

The use of the phosphazene base P2‐Et(a) as a promoter for the anionic polymerization of hexamethylcyclotrisiloxane (D3Me) or hexaethylcyclotrisiloxane (D3Et) initiated by an organolithium compound leads to well‐defined polysiloxanes. At low conversion (< ca. 9%) the polymerization of D3Me behaves like a living polymerization, however, polymers with a narrow molecular weight distribution (M̄w/M̄n < 1.1) are obtained up to much higher conversions (ca. 70%). Kinetic data and NMR spectroscopy revealed the existence of a dynamic equilibrium between complexed and uncomplexed lithium silanolates. Below ambient temperature several different types of aggregates were indicated. The occurrence of an acceleration was observed after ca. 9% conversion.
Temperature rising elution fractionation of a random ethene/styrene copolymer
Authors: Thomann Yi , Sernetz Friedrich G. , Thomann Ralf , Kressler Jörg , Mülhaupt Rolf
Published: April 2003

A random ethene/styrene copolymer containing 13.8 mol‐% styrene was prepared with the Ziegler‐Natta catalyst system Me2Si(Me4Cp)(N‐t‐butyl)TiCl2/methylaluminoxane and characterized by means of preparative temperature rising elution fractionation (TREF) combined with size exclusion chromatography, NMR, differential scanning calorimetry and wide‐angle X‐ray scattering analyses of the copolymer fractions. Efforts are made to describe the distribution of the styrene content of the copolymers using the Stockmayer‐Tacx distribution function. Both, comonomer distribution and molar mass distribution strongly support the presence of a single type of catalytically active center.
Radically initiated polymerization of a methacryloylamido‐terminated saccharide, 2. Copolymerization with 2‐hydroxyethyl methacrylate
Authors: Badey Bérangère , Boullanger Paul , Domard Alain , Cros Philippe , Delair Thierry , Pichot Christian
Published: April 2003

Kinetics of radically initiated copolymerization of 6‐deoxy‐6‐methacryloylamido‐D‐glucopyranose (MAG) with 2‐hydroxyethyl methacrylate (HEMA) was investigated at 60°C in water using 4,4′‐azobis(4‐cyanopentanoic acid) as initiator. Reactivity ratios of the binary system were determined to be rHEMA = 3.50 and rMAG = 0.60, indicating a strong copolymerization drift as polymerization proceeds. Copolymers with homogeneous composition were prepared using a simple and easy method based on the knowledge of the consumption rate of each monomer. These copolymers were then characterized with regard to composition (by 1H NMR) and physicochemical properties in aqueous media (using SEC with MALLS and refractometry detection and viscosimetric measurements).
Polyketone materials: control of glass transition temperature and surface polarity by co‐ and terpolymerization of carbon monoxide with higher 1‐olefins
Authors: Abu‐Surrah Adnan S. , Wursche Roland , Rieger Bernhard
Published: April 2003

Highly soluble alternating 1‐olefin/carbon monoxide copolymers with olefin monomers (H2CCHR) containing 4, 5, 6, 10, 14, 16 and 18 C‐atoms in the R‐substituents were prepared by the use of dicationic palladium(II) phosphine catalysts and an optimized amount of methanol as activator. In terpolymerization experiments the influence of icosene‐CO or octadecene‐CO units, distributed randomly along a propene‐CO or ethene‐CO copolymer backbone, on molecular weight, glass transition temperature and on the surface polarity of films casted from solution has been investigated. As the length of the α‐olefin side chain increases, the glass transition temperature (Tg) of the copolymer is reduced from room temperature to almost −60°C. For octadecene‐CO and icosene‐CO copolymers side chain crystallization occurs, leading to elastic materials. Contact angle measurements, performed on water drops located on the surface of selected co‐ and terpolymer films demonstrate the wide range of surface polarity which can be covered by simple copolymerization of polar CO groups with apolar alkenes.
Synthesis and properties of (D)‐ and (L)‐lactide stereocopolymers using the system achiral Schiff's base/aluminium methoxide as initiator
Authors: Wisniewski Muriel , Borgne Alain Le , Spassky Nicolas
Published: April 2003

The polymerization of lactides with various D/L enantiomeric compositions using achiral Schiff's base/aluminium methoxide as initiator (SALENAlOCH3) in dichloromethane solution at 70°C is reported. The conversion was kept below 70% in order to limit transesterification reactions. The polymers obtained after precipitation show a narrow molecular weight distribution (ratio of weight‐ to number‐average molecular weights Mw/Mn = 1,1–1,2) and an optical rotation higher than that expected from the optical purity of the starting monomers. The examination of the thermal properties reveals that whatever their enantiomeric composition all the prepared polymers are crystalline. This unusual behavior is explained by an end‐chain propagation mechanism producing stereocopolymers with long enantiomeric sequences, i.e., increased isotacticity as substantiated by an examination of the microstructure of the polymers by means of 13C nuclear magnetic resonance. A stereocomplex formation was observed for stereocopolymers with optical purities below 40%.