bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cationic polymerization of bis(1‐alkylvinyl)benzenes and related monomers, 5. New thermostable polyindanes
Authors: Nuyken Oskar , Leitner Michael B. , Maier Gerhard 
Published: April 2003

AbstractThe cationic cyclopolymerization of six monomers of the type “1,4‐bis(alk‐2‐en‐2‐yl)benzene” is described. The length of the unsaturated chains of the monomers ranges from 3 (propenyl) to 8 (octenyl) carbon atoms. The polymerization yields polyindanes containing different isomeric indane structure elements, which have alkyl substituents ranging from methyl to hexyl groups. The number of carbon atoms in the alkyl side chains greatly influences the glass transition temperature Tg, which is depressed from 246°C (methyl‐substituted polyindane) to 26°C (hexyl‐substituted polyindane). Thermal stability is also affected, though far less than Tg: the temperature, at which the material has lost 2% of its original weight is lowered from 420°C to 340°C. The polyindanes are soluble in a number of organic solvents. Their degree of polymerization is limited by a side reaction which provides non‐reactive end groups. Thus, the number‐average molar masses obtained are between 2800 and 4300 g/mol.
End group identification and molecular weight determination of a diels‐alder ladder polymer
Authors: Godt Adelheid , Schlüter Arnulf‐Dieter 
Published: April 2003

AbstractThe end groups of the double‐stranded polymer 2 were identified using NMR spectroscopy and end‐capping reactions. The number‐average molecular weight of a representative sample of 2 was determined as P̄n = 45.
Polyacetylenes with cholesteryl side‐groups: synthesis, linear and non‐linear optical properties of soluble conjugated polymers
Authors: Moigne Jacques Le , Hilberer Alain , Kajzar François 
Published: April 2003

AbstractNew polyacetylenes with cholesteryl side‐groups with different spacer lengths are polymerized through classical metathesis reaction in solution with the transition metal halides WCl6, MoCl5, and TaCl5. The highest polymerization yield and the best average molecular weight are obtained with the cholesteryl 4‐pentynoate (CP5) with the 1 ,4‐dioxane/WCl6 couple and the measured values are, respectively, 87% and 15 · 104. All of the other esters, cholesteryl propynoate or cholesteryl 10‐undecynoate give low polymerization yields. Poly(CP5) is a red transparent solid; it can be dissolved in common organic solvents and can be cast from solution into films. The solid‐state film presents a transition to a thermotropic liquid‐crystalline phase at 189°C and a transition to the isotropic phase at 189°C. A progressive decoloration occurs in solution and in the liquid‐crystalline phase. The results are interpreted as conformational changes of the polyene planar chain in a less conjugated backbone. The third‐order susceptibility χ3 measured by third harmonic generation on the red polymer lies in the range of 10−21 V2·m−2 in accord with the low content of the active part in the molecule and to a moderate length of conjugation of this highly crowded polyacetylenic chain.
On the conformation and the crystalline structure of an ethylene‐chlorotrifluoroethylene alternating copolymer
Authors: Guerra Gaetano , Rosa Claudio De , Iuliano Mauro , Petraccone Vittorio , Corradini Paolo , Pucciariello Rachele , Villani Vincenzo , Ajroldi Giuseppe 
Published: April 2003

AbstractThe conformation and the packing of the chains of the alternating ethylene‐chlorotrifluoro‐ethylene copolymer (ECTFE), in the crystalline phase, are investigated by X‐ray diffraction analysis, by calculations of the conformational energy and by calculations of the Fourier‐transforms of models. These analyses suggest that the crystalline form of ECTFE is a mesomorphic form, with a pseudo‐hexagonal packing of the axes of nearly trans‐planar chains (interchain distances of 5,69 Å) and a nearly complete translational and rotational disorder along the chain axis.
Preparation and properties of macromolecular complexes consisting of chitosan derivatives and potassium metaphosphate
Authors: Kubota Naoji , Kikuchi Yasuo 
Published: April 2003

AbstractGlycol chitosan (GC) and methyl glycol chitosan (MGC) were, individually, reacted with potassium metaphosphate (MPK) to form a series of water‐insoluble macromolecular complexes (MC) in aqueous solution at different hydrogen ion concentrations (GC‐MPK and MGC‐MPK systems). GC was reacted with MPK in the presence of CaCl2 (GC‐MPK‐CaCl2 system) as well as in the absence of CaCl2. The properties of MC obtained were studied. On the basis of elemental analysis, solubilities, and thermogravimetry analysis, it is suggested that the molecular structure of each MC depends on the hydrogen ion concentration and whether Ca2+ ion is present or not. MC prepared at pH 1,0 are composed of a relatively loose network including a small quantity of MPK, whereas those MC prepared at neutral and higher pH are composed of a relatively tight network including a large quantity of MPK. As compared with MC in the GC‐MPK system, those in the GC‐MPK‐CaCl2 system are anticipated to have a rather tightly bound network structure due to the cross‐linkings through Ca2+ ions.
Polymerization in inverse microemulsions, 4 locus of initiation by ammonium peroxodisulfate and 2,2′‐azoisobutyronitrile
Authors: Vašková Viera , Hloušková Zuzana , Bartoň Jaroslav , Juraničová Viera 
Published: April 2003

AbstractThe locus of the initiation using the water‐soluble radical initiator ammonium peroxodisulfate (APS) and/or the partially water‐soluble radical initiator 2,2′‐azoisobutyronitrile (AIBN) in the inverse microemulsion system toluene/water (mass ratio 10:1) was studied. The homopolymerization and/or copolymerization of the water‐soluble monomer acrylamide (AAM) with the oilsoluble methyl methacrylate (MMA) was investigated. It was found that the locus of initiation by APS in the given system is the water micropool, and the locus of initiation by AIBN is the interlayer between the water micropool and the toluene macrophase.
Thermotropic polyesters, 8, comparison of two methods of synthesis of regular liquid‐crystalline multiblock copolymers
Authors: Piraner Olga N. , Tenkovtsev Andrey V. , Bilibin Alexander Yu. 
Published: April 2003

AbstractTwo methods of synthesis of regular liquid‐crystalline (LC) multiblock copolyesters are compared. A new method for the synthesis of polyesters with increased length of mesogenic units is given. This method is based on the preparation of intermediate oxalate‐groups‐containing polymers which are hydrolyzed in the next stage. The difference consists in the structure of the initial complex monomer. The new complex monomer makes it possible to obtain LC polyesters with seven 1,4‐phenylene fragments in the mesogenic unit by a simpler route.
Water‐soluble photoresins based on azosulfonates
Authors: Dauth Jochen , Nuyken Oskar , Strohriegl Peter , Voit Brigitte 
Published: April 2003

AbstractWater‐soluble polymers with pendant azosulfonate groups were synthesized by radical copolymerization of 3‐vinylphenylazosulfonate with methyl methacrylate or styrene. The copolymerization parameters were determined for these systems. Furthermore, photoactive polymers were obtained by reaction of poly[(methacryloyl chloride)‐co‐(methyl methacrylate)] with azosulfonates containing phenolic or amino groups. Due to their solubility in water and their photocrosslinking behaviour, these polymers are attractive candidates for photoprinting and photoresist materials.
Synthesis of block copolymers from 1‐chloro‐1‐octyne and other acetylenes through their sequential living polymerization by MoOCl4n‐Bu4SnEtOH
Authors: Akiyoshi Kazunori , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractBlock copolymerizations of 1‐chloro‐1‐octyne (1‐ClO) with several substituted acetylenes were examined by means of living polymerization. o‐(Trifluoromethyl)phenylacetylene (o‐CF3PA), o‐(trimethylsilyl)phenylacetylene (o‐Me3SiPA), 1‐chloro‐2‐phenylacetylene (1‐ClPA), p‐butyl‐o,o,m,m‐tetrafluorophenylacetylene (p‐BuF4PA), and tert‐butylacetylene (t‐BuA) were used as comonomers, and the MoOCl4‐n‐Bu4Sn‐EtOH (mole ratio 1:1:1) catalyst, which is known to effect living polymerization of substituted acetylenes, was employed. When o‐CF3PA and 1‐CIPA were the comonomers in combination with 1‐CIO, block copolymers were exclusively obtained in both orders of monomer addition. In the cases of o‐Me3SiPA and p‐BuF4PA as comonomers, the copolymerizations initiated from 1‐CIO produced block copolymers selectively, whereas the homopolymers of o‐Me3SiPA and p‐BuF4PA also formed if the order of monomer addition was reversed. The pair of 1‐CIO and t‐BuA did not selectively yield block copolymers irrespective of the order of monomer addition. Thus, block copolymerization occurred between 1‐CIO and monomers that show high “livingness” and close reactivities.
Molecular characterization of water‐soluble, cationic polyelectrolytes
Authors: Griebel Thomas , Kulicke W.‐Michael 
Published: April 2003

AbstractPoly{acrylamide‐co‐[2‐(acryloyloxy)ethyltrimethylammonium chloride]} (1), Poly{acrylamide‐co‐[2‐(methacryloyloxy)ethyltrimethylammonium chloride]} (2) and Poly{acrylamide‐co‐[3‐(acryloylamino)propyltrimethylammonium chloride]} (3) with cationic monomeric unit mole fractions of 8, 25, and 50 mol‐%, and the corresponding homopolymers were characterized with respect to their molecular dimensions in 1 M sodium chloride solution at 25°C in the molecular weight range from 200000 to 16000000, using light‐scattering and viscometric measurements. It was possible to establish correlations between molecular weight, intrinsic viscosity and radius of gyration. Whereas a steady increase in the exponents of the [η] vs. M‐ and 〈R2G〉0,5 vs. M‐relationships can be observed with increasing charge density, there is an initial decrease in the values of the exponents for 2 and 3, when 8 mol‐% of the cationic monomer is inserted into poly‐acrylamide. If the charge density is increased further, these values can also be seen to rise steadily. The findings are explained by the different structures in solution, which are formed by the copolymers and homopolymers investigated due to their chemical structure. The radii of gyration were calculated from the intrinsic viscosities with the aid of the Flory‐Fox equation. However, neither the results obtained with the Flory‐Fox constant Φ0= 3,69. 1024 mol−1, nor those with the value of Φ0= 2,10. 1024 mol−1 showed good agreement with the experimentally recorded data.
Cationic polymerization of 1,2‐epoxy‐3‐nitropropane in the presence of ethylene glycol, 1. Lower oligodiols obtained according to the activated monomer mechanism
Authors: Lagarde Florence , Reibel Léonard , Franta Emile 
Published: April 2003

AbstractThe early stage of cationic polymerization of 1,2‐epoxy‐3‐nitropropane in the presence of ethylene glycol and borontrifluoride etherate is examined. It is shown that the reaction proceeds according to the Activated Monomer Mechanism: initiation and propagation involve the nucleophilic attack of an hydroxyl end‐group moiety onto a protonated monomer molecule; this attack takes place on the carbon atom located in the β‐position with regard to the CH2NO2 group.
Polyarylenes and poly(arylenevinylene)s, 9 The oxidized states of a (1,4‐phenylene) ladder polymer
Authors: Scherf Ullrich , Bohnen Angelika , Müllen Klaus 
Published: April 2003

AbstractThe oxidized states of double‐stranded, planar (1,4‐phenylene)‐type ladder polymers are characterized by means of UV/VIS/NIRNIR: Near infrared.
spectroscopy and cyclic voltammetry. The oxidation with antimony pentachloride or iron trichloride proceeds as a two‐step process; first, radical cationic (polaronic) species are generated, followed by the formation of dicationic (bipolaronic) ones. Especially the polymeric radical cations formed possess an outstanding chemical stability. The findings of cyclovoltammetric investigations are in full agreement with the chemical oxidation experiments.
Kinetics of polymerization of mixed diacetylene single crystals determined from dielectric measurements
Authors: Orczyk Maciej , Pater Ewa , Sworakowski Juliusz 
Published: April 2003

AbstractResults of investigations on the kinetics of thermal polymerization of mixed single‐crystalline diacetylenes are reported. The polymerization was studied at 333 K on a series of mixed 1 (pTS)–3 (pFBS) crystals of various compositions. The polymer contents were determined from the measurements of electric permittivities of the samples during polymerization. A simple qualitative model was put forward to explain changes in the kinetics of polymerization as function of the composition of mixed crystals. At early stages of polymerization, the process of initiation of the growth of polymer chains seems to be dependent on the concentration of defects associated with a misfit between pTS and pFBS molecules.
Molecular mobility in the adsorption layer and chain orientation in strained poly(dimethylsiloxane) networks by 2H NMR
Authors: Litvinov Victor M. , Spiess Hans Wolfgang 
Published: April 2003

AbstractThe molecular mobility at the elastomer/active filler interface is studied in Aerosil‐filled poly(dimethylsiloxane) networks. It is shown that in unstrained samples two regions of different local chain mobility can be distinguished, namely chain units in the adsorption layer and outside of it. The fraction of chain units with relatively low mobility in the adsorption layer is estimated. In a uniaxially strained sample, immobilization of chain units near the filler surface is observed at temperatures up to 20 K above the melting temperature of an unstrained sample. The network structure of unfilled and filled networks is probed by analysis of the quadrupolar splitting in 2H solid‐echo spectra of uniaxially strained samples. The local chain order at a given elongation is larger by a factor of 1,5–2 in the filler system. This is interpreted in terms of an increased number of effective cross‐links and the differences between macroscopic and microscopic strains.
Steric effects in 3‐substituted polythiophenes: comparing band gap, nonlinear optical susceptibility and conductivity of poly(3‐cyclohexylthiophene) and poly(3‐hexylthiophene)
Authors: Goedel Werner A. , Somanathan Narayana Sastri , Enkelmann Volker , Wegner Gerhard 
Published: April 2003

AbstractWe present the synthesis, characterization (NMR, mass spectroscopy, IR) and polymerization of 3‐cyclohexylthiophene. Although anodic polymerization is ineffective, it was possible to polymerize 3‐cyclohexylthiophene with FeCI3 as the oxidizing reagent, the resulting poly(3‐cyclohexylthiophene) (PC6T) having a peak molar mass of 73 000 g · mol−1. NMR‐Investigations reveal that the coupling ocurred mainly via the 2,5‐positions, and the band gap, as determined from UV‐vis spectroscopy and cyclic voltammetry, was 2,3–2,4 eV. The nonlinear susceptibility χ(3)(−3ω; ω ω ω) of the neutral polymer and the electrical conductivity of the CIO4− and PF−6 salts were determined. The effect of the steric requirements of the cyclohexyl substituent was estimated by comparing the polymer to a poly(3‐hexylthiophene) (PN6T) of the same molar mass and with a comparable number of defects (mainly head‐to‐head and tail‐to‐tail coupling of the subunits). In the case of PC6T the band gap of the neutral polymer is larger by 0,3 to 0,4 eV, the nonlinear susceptibility has approximately half the value, and the electrical conductivity of the oxidized polymer is two orders of magnitude lower than the corresponding values of PN6T. These effects are explained by the increased sterical requirements of the cyclohexyl substituent, which forces the thiophene rings out of a coplanar conformation and thus reduces the conjugation length.
New poly(amide‐imide) syntheses, 4 Poly(amide‐imide)s derived from 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene and various bis(trimellitimide)s
Authors: Yang Chin‐Ping , Hsiao Sheng‐Huei , Lin Jiun‐Hung 
Published: April 2003

AbstractFifteen bis(trimellitimide)s 2a–o were prepared by condensation of the corresponding aliphatic or aromatic diamines with trimellitic anhydride. A series of structurally new poly(amideimide)s were synthesized by the direct polycondensation of these bis(strimellitimide)s with 2,5‐bis(4‐aminophenyl)‐3,4‐diphenylthiophene using triphenyl phosphite and pyridine as condensing agents in N‐methyl‐2‐pyrrolidone (NMP). The resultant poly(amide‐imide)s have inherent viscosities in the range between 0,72 and 2,73 dL/g at 30°C in N,N‐dimethylacetamide (cf. Tab. 2). The polymers are amorphous and readily soluble in polar aprotic solvents such as N,N‐dimethylacetamide (DMAc) and NMP. Transparent and tough films can be cast from their solutions. Most aliphatic‐aromatic poly(amide‐imide)s show a glass transition in the range between 203 and 242°C in their differential scanning calorimetry (DSC) traces, whereas the wholly aromatic poly(amide‐imide)s show no discernible transition before decomposition. The thermal stability of the polymers was evaluated by thermogravimetry which showed the 10% weight‐loss temperatures in the range between 414 and 459°C in air and between 451 and 578°C in a nitrogen atmosphere for the aliphatic‐aromatic poly(amide‐imide)s and above 500°C in both air and nitrogen atmosphere for the wholly aromatic poly(amide‐imide)s.
Elementarprozesse der Ziegler‐Katalyse, 6 Ethylen‐ und propenhomopolymerisation mit den stereorigiden katalysatorsystemen iPr[FluCp]ZrCl2/MAO und Me2Si[Ind]2ZrCl2/MAO
Authors: Herfert Norbert , Fink Gerhard 
Published: April 2003

AbstractThe ethylene and propene homopolymerization was investigated by means of the Cs‐symmetric [2,4‐cyclopentadien‐1‐ylidene(isopropylidene)fluoren‐9‐ylidene]zirconium dichloride/methylaluminoxane (iPr[FluCp]ZrCl2/MAO) and the C2‐symmetric [(dimethylsilylene)bis(η5‐inden‐1‐ylidene)]zirconium dichloride/methylaluminoxane (Me2Si[Ind]2ZrCl2/MAO) catalyst systems in toluene. Surprisingly, the Cs‐symmetric catalyst polymerizes propene faster than ethylene. The main results of the kinetic analysis are a first‐order dependence on the concentration of Zr but a bell‐shape in the plot of the polymerization rate versus log([Al]: [Zr]). This is true for both catalyst systems. Furthermore with increasing [Al]:[Zr] ratio the fraction of rmrr pentads is decreased continuously with the Cs‐symmetric catalyst; in the same direction the molecular weights are decreased. On the contrary with the C2‐symmetric catalyst the stereospecificity and the molecular weights remain constant. The kinetic results reflect the complex role of the MAO, i.e. the existence of sterically more and more tight contact species between metallocene and MAO components with increasing [Al]: [Zr] ratio. The different behaviour of the two catalyst systems concerning stereospecificity and molecular weights of the polymers are due to different symmetry and different size of the angle between the planes of the π‐ligand systems.
Solvent effect on the propagation rate constant in the radical polymerization of bis(2‐ethylhexyl) itaconate
Authors: Sato Tsuneyuki , Shimizu Takehiro , Seno Makiko , Tanaka Hitoshi , Ota Tadatoshi 
Published: April 2003

AbstractPolymerization of bis(2‐ethylhexyl) itaconate (1) with dimethyl azobis(isobutyrate) (2) was carried out at 50°C in various solvents. Polar solvents caused a significant decrease in the polymerization rate (Rp) and the molecular weight of resulting poly(1). The propagating poly(1) radical could be observed as a five‐line ESR spectrum in the actual polymerization systems used. The stationary concentration of poly(1) radical was determined by ESR to be 4,2–6,4 · 10−6 mol · L−1 at 50°C when the concentrations of 1 and 2 were 1,03 and 3,00 · 10−2 mol · L−1. Using Rp the monomer concentration and the polymer radical concentration, the propagation rate constant (Kp) was estimated to be 1,4–6,8 L · mol−1 · s−1, depending on the solvents used. The kp value was smaller in more polar solvents. The solvent effect is explained in terms of the solvent affinity for the propagating polymer chain.
Studies on silicone‐grafted copolyimides, 3. Synthesis of soluble polyimide/polydimethylsiloxane graft copolymer and application to separation membrane
Authors: Akiyama Ei‐ichi , Takamura Yuriko , Nagase Yu 
Published: April 2003

AbstractPolyimide/polydimethylsiloxane (PI/PDMS) graft copolymer was prepared following the macromonomer method. First, 3‐(3,5‐diaminobenzyloxy)propyl‐terminated polydimethylsiloxane (DAB‐PDMS) was prepared by hydrosilylation of allyl 3,5‐dinitrobenzyl ether with hydrosilyl‐terminated PDMS, followed by catalytic reduction of the two nitro groups. PI/PDMS graft copolymer was synthesized by polycondensation of DAB‐PDMS with 4,4′‐oxydianiline (ODA) and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA), followed by chemical imidation. The average degree of polymerization of the PDMS chain was in the range between 7 and 25. The resulting graft copolymers were soluble in several organic solvents. Membranes were prepared by solvent casting, followed by heating at 220°C in vacuo, upon which the membranes became hardly soluble in organic solvents. The gas permeability coefficients of the graft copolymer membranes were much greater than those of the polyimide homopolymer and of the same order as that of a PDMS membrane. Furthermore, a selective permeation of organic liquids, e.g., tetrahydrofuran, acetone and acetonitrile, was observed in the pervaporation of aqueous organic liquids through the copolymer membrane.
Polyimides, 1. Studies on the thermal curing of imide model compound with tricyclic structure by nuclear magnetic resonance and mass spectra
Authors: Su Ching‐Yie , Lee Yu‐Der 
Published: April 2003

AbstractA model imide with a tricyclic structure was synthesized by reacting 3‐phenyltricyclo[6.2.2.02,7]‐2,11‐dodecadiene‐5,6 : 9,10‐tetracarboxylic dianhydride with aniline. The thermogravimetry curve showed that it degraded at about 300°C, and its differential scanning calorimetry curve was found to be similar to that of its corresponding polyimides. The thermal curing of this model imide was studied in detail. A curing mechanism was proposed based on the analysis of the cured product using NMR and mass spectroscopy. The results show that the curing mechanism started with a reverse Diels‐Alder reaction, forming an intermediate which either dehydrogenated or further decomposed into 1,1‐diphenylethylene, andN‐phenylsuccinimide. The 1,1‐diphenylethylene andN‐phenylsuccinimide would either polymerize or become hydrogenated to form 1,1‐diphenylethane andN‐phenylsuccinimide, respectively.
Catalytic hydrolysis of activated aromatic esters by branched polyamines
Authors: Van Beylen Marcel , Samyn Celeste 
Published: April 2003

AbstractTwo polymeric amines, poly[(2‐aminopropyl)propyleneimine] (PI) and poly[(2‐aminoethyl)‐ethyleneimine] (PII), as well as the dodecyl‐ and imidazolylmethyl‐substituted derivative of PI, were used for the hydrolysis of p‐nitrophenyl acetate (PNPA), 4‐acetoxy‐3‐nitrobenzoic acid (ANBA) and some of their homologues, in order to elucidate the relations between their overall structure and their catalytic activities. All reactions were carried out at 28,7°C in aqueous solution, and followed spectrometrically using a catalyst concentration in large excess with respect to the substrate concentration (10−4 mol · L−1). The reactions were found to obey pseudo‐first order kinetics. By plotting log[substrate] against time, k2(cat) and consequently the second‐order rate constants k2 were evaluated. The above mentioned polymers show hydrolysis constants which exceed the values obtained for tailor‐made partially substituted polyethyleneimines. Even when linear polythyleneimine was substituted for 42% with 2‐(2‐aminopropylamino)propyl groups, PI and PII give k2 values which are 8 times higher towards PNPA, and 10 times higher towards ANBA, under the same reaction conditions.