bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas transport properties of linear and crosslinked side‐chain liquid crystalline polymers with variable spacer lengths
Authors: Chen Deng‐Shan , Hsiue Ging‐Ho 
Published: April 2003

AbstractA series of side‐chain liquid crystalline polymers (side‐chain LCPs) with different flexible spacer lengths and various degrees of crosslinking were synthesized and characterized. The transport properties of O2, N2, CO2 and CH4 in these polymers were measured by using permeation and sorption methods. The values of diffusion and solubility coefficients were found to be significantly affected by the crosslinking reaction. In contrast to conventional crosslinked polymers, the values greatly increase as the degree of crosslinking increases. The reason might be the use of the flexible oligodimethylsiloxane crosslinking agent and the low solubility of gases in the liquid crystalline regions. The transport properties were also demonstrated to depend strongly on the flexible spacer length. This was ascribed to the fact that different liquid crystalline phases are formea. For the smectic phase, the diffusion and solubility coefficients are lower than those found in the nematic one.
Copolymerization of ethylene and propene with a TiCl4/MgCl2‐Al(C2H5)3 catalyst system using a stopped‐flow method
Authors: Soga Kazuo , Ohgizawa Masa‐aki , Shiono Takeshi 
Published: April 2003

AbstractCopolymerization of ethylene with a small amount of propene was conducted with a TiCl4/MgCl2‐Al(C2H5)3 catalyst system using a stopped‐flow method. With an increase in the polymerization time from 0,035 to 0,145 s, the copolymer yield increases linearly but the number‐average molecular weight of the copolymer showed a tendency of saturation. The rate constants of the propagation reaction as well as the concentrations of active sites were estimated using these data. On the other hand, the 1H NMR spectra of copolymer did not display the resonances due to CC double bonds which should be formed by chain transfer with monomer and/or by β‐hydrogen elimination. It was also found that the crystallinity of the copolymer decreases to a great extent upon incorporation of even a very small quantity of propylene units. From these results, it was concluded that the apparent rate of copolymerization is not controlled by monomer diffusion through the polymer films. Rather the transfer reaction with Al(C2H5)3 might predominantly take place during the copolymerization.
Transport properties of polyphosphates related to natural teichoic acids
Authors: Wódzki Romuald 
Published: April 2003

AbstractThe paper deals with transport functions of natural polyphosphates, i.e. wall‐and lipoteichoic acids (WTA, LTA) appearing in Gram‐positive bacteria. The results concerning the separation of magnesium and calcium ions in a membrane system, simulating bacteria cell wall, are presented. The system was composed of a solid polymer membrane and a liquid membrane, containing poly(trimethylene phosphate) and α‐hydroxy‐ω‐(2‐ethylhexyl)‐poly(trimethylene phosphate) applied as synthetic analogues of WTA and LTA, respectively. Up‐hill transport with reference towards magnesium ions was observed.
Kinetic and ESR studies on radical polymerization. ESR and kinetic evidences for the penultimate effect in the radical‐initiated copolymerization of N‐cyclohexylmaleimide and bis(2‐ethylhexyl) itaconate in benzene
Authors: Sato Tsuneyuki , Kawasaki Shinji , Seno Makiko , Tanaka Hitoshi , Kato Kenji 
Published: April 2003

AbstractThe copolymerization of N‐cyclohexylmaleimide (1) (M1) and bis(2‐ethylhexyl) itaconate (2) (M2) with dimethyl 2,2′‐azoisobutyrate (3) as an initiator was carried out at 50°C in benzene. Monomer reactivity ratios were estimated as r1 = 0,34 and r2 = 0,38. The copolymerization rate (Rp) and the molecular weight of the resulting copolymer increased with increasing concentration of 1 when the total concentration of comonomers was fixed at 1,00 mol. L−1. Rp was proportional to [3]0,5, indicating a usual bimolecular termination in the copolymerization. An electron spin resonance (ESR) spectrum of the propagating polymer radicals was observable in the actual copolymerization system at 50°C. The spectrum of the copolymerization system is inexplicable in terms of any superposition of spectra observed in the corresponding homopolymerization systems, revealing that some penultimate monomeric unit causes a change in the ESR spectrum, that is, the structure of propagating polymer radical. The apparent rate constant of propagation (kp) and termination (kt) were estimated by ESR. The kp values (1,5–50 L · mol−1 · s−1) are fairly higher than those estimated on the basis of the terminal model, affording another piece of evidence for the penultimate effect. The kt value (1,8–5,4·103 L · mol−1 · s−1) shows a behaviour similar to that of the intrinsic viscosity of the resulting copolymer on varying the monomer feed composition, which seems to reflect diffusion‐control of termination reactions.
Multiblock poly(ether‐ester‐amide)s based on polyamide‐6 and poly(ethylene glycol), 2 Effect of composition and soft‐segment length on the structure of poly(ether‐ester‐amide)s as revealed by X‐ray scattering
Authors: Apostolov Anton A. , Bosvelieva Eliana , Du Chesne Alexander , Goranov Konstantin , Fakirov Stoyko 
Published: April 2003

AbstractIsotropic unannealed and annealed melt‐pressed and quenched samples of segmented multiblock poly(ether‐ester‐amide)s based on polyamide‐6 and poly(ethylene glycol)s (PEGs) of molecular weights 400 and 1000 with various hard/soft segment weight ratios were investigated. The effect of composition, segment length and annealing temperature on the crystal structure was studied by differential scanning calorimetry, wide‐angle and small‐angle X‐ray scattering. In addition to the γ‐phase, one of the unannealed samples having relatively long hard and soft segments exhibits a high amount of α‐phase. This is assumed to be due to the high flexibility of the PEG segments, linking the polyamide blocks thus enhancing their mobility. The lack of hydrogen bonds between the PEG segments facilitates crystallization of the polyamide segments in the more perfect α‐modification, which is the most pronounced in the above mentioned sample. Part of the α‐phase transforms into the α‐phase upon annealing in all copolymer samples studied, similarly to polyamide‐6.
Low‐molecular‐weight poly(imide‐amide)s obtained by copolycondensation of 4,4′methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid in N‐methyl‐2‐pyrrolidone, 1. The microstructure studied by 1H and 13C NMR
Authors: Sintès‐Zydowicz Nathalie , Pham Quang Tho , Michaud Philippe 
Published: April 2003

AbstractLow‐molecular‐weight poly(imide‐amide)s (PIA) obtained by polycondensation at 180°C of 4,4′ ‐methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid were studied by 1H and 13C NMR. Complementary 1H and 13C information was used to determine the distribution of II, IA, AA sequences and to show that the repartition of imide (I) and amide (A) groups along the chains is random. According to the composition of the monomer mixture, a slight deficiency of I is reproducibly observed. Non‐reacted benzoic acid is found, and unexpected traces of urea and amic acid groups are present in the PIA chains.
Synthesis of telechelics with furanyl end‐groups, 2 Radical polymerization with cc‐bond splitting initiators and network formation with unsaturated polyesters via diels‐alder additions
Authors: Edelmann Dirk , Ritter Helmut 
Published: April 2003

AbstractNew CC‐bond splitting initiators with two furanyl groups were prepared: 1,2‐di‐2‐furanyl‐1,2‐diphenyl‐1,2‐bis(trimethylsiloxy)ethane (4a), 1,2‐di‐2‐furanyl‐1, 2‐di‐p‐tolyl‐1, 2‐bis(trimethylsiloxy)ethane (4b) and 1,2‐di‐2‐furanyl‐1, 2‐dimesityl‐1,2‐bis(trimethylsiloxy)ethane (4c). Radical polymerizations of styrene and (meth)acrylates with the new CC‐bond splitting initiators were performed in solution at temperatures between 80–105°C. The telechelic oligomers were characterized by GPC and NMR spectroscopy, proving a furanyl functionality of two. The kinetics of the Diels‐Alder reactions between the furanyl‐terminated telechelics and dienophiles such as maleic anhydride and dimethyl maleate were measured under pseudo‐first‐order conditions. Addition of the telechelics to unsaturated polyesters prepared from maleic anhydride and diols led to a solid material with network structure.
Renewable resources, 1. Branching and crosslinking of an unsaturated oligoester with furfurylamides and sorbic acid amides via diels‐alder additions
Authors: Reinecke Martin , Ritter Helmut 
Published: April 2003

AbstractThe unsaturated polyester 1 prepared from maleic anhydride and 1,4:3,6‐dianhydro‐D‐glucitol was modified with the sorbic acid amides and furfurylamides 2, 3, 6, 7 and 8 via Diels‐Alder (DA) reactions. The cycloadditions with the monodienes 2 and 3, the bisdiene 6 and the trisdiene 7 led to branched derivatives, whereas the DA reaction with the tetradiene 8 yielded a crosslinked material. All compounds contain a high amount of molecules obtained from renewable resources.
Sulfur‐Containing polymers. New polythiocarbonates and polydithiocarbonate based on 4,4′‐isopropylidenedibenzenethiol
Authors: Bandiera Milena , Berti Corrado , Manaresi Piero , Marianucci Elisabetta , Pilati Francesco , Poloni Marino 
Published: April 2003

AbstractNew sulfur‐containing polycarbonates have been prepared by interfacial polycondensation of 4,4′‐isopropylidenedibenzenethiol with phosgene, bisphenol‐A bischloroformate and bisphenol‐A polycarbonate oligomers (OH/OCOCl terminated); high‐molecular‐weight polymers were obtained. The influence of the nature of the phase transfer catalyst on the yield and on the molecular weight of the polymers was studied. From thermogravimetry (TG) analysis it was possible to observe that the substitution of the oxygen atoms by sulfur atoms leads to less thermally stable polymers compared with the corresponding polycarbonate (bisphenol‐A polycarbonate).
Convenient synthesis of polymers containing terminal aldehyde and ketone moieties by selective oxidation of polymeric terminal diols with an oxoaminium salt
Authors: Yoshida Eri , Takata Toshikazu , Endo Takeshi 
Published: April 2003

AbstractSynthesis of polymers with aldehyde or ketone groups at both chain ends was carried out by oxidation of polymeric terminal diols with an oxoaminium salt (OAS), the oxidized form of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl. Terminal diols of polyethers, polyesters, polycarbonates, polybutadiene, and hydrogenated polybutadiene were oxidized with 2,0 equiv. of OAS in dichloromethane at room temperature in the dark. The corresponding aldehyde‐and/or ketoneterminated polymers were obtained in high yields with high conversion of OH group and little change in molecular weight. Poly(ethylene glycol) and poly(ethylene adipate) terminal diols were oxidized with low efficiency. Especially, in the case of poly(ethylene glycol), intermolecular reactions occurred to afford high molecular weight polymer. The ratio of aldehyde (CHO) to ketone (CO) groups in the oxidized polymer originating from the hydrogenated polybutadiene terminal diol was calculated to be 37/63.
Group transfer polymerization of methyl methacrylate and butyl acrylate in tetrahydrofuran with oxy anions as catalysts
Authors: Schmalbrock Urban , Bandermann Friedhelm 
Published: April 2003

AbstractGroup transfer polymerization (GTP) of methyl methacrylate (MMA) and butyl acrylate (BA) in tetrahydrofuran with (1‐methoxy‐2‐methyl‐1‐propenyloxy)trimethylsilane (MTS) as initiator and tetrabutylammonium 3‐chlorobenzoate, tetrabutylammonium bi‐3‐chlorobenzoate and tetrabutylammonium bibenzoate as catalysts was investigated. It was found, that the reaction of MTS with all catalysts in the absence of monomers yields the same reaction products as common GTP catalysts. Furthermore, the time‐conversion curves of MMA and BA exhibit induction periods proving the assumption, that the first addition step of the monomer to the initiator is slower than the propagation reaction. With respect to molecular‐weight control, oxy anions are superior to tetrabutylammonium cyanide (TBACN) due to the missing capability of oxy anions to initiate an anionic polymerization, and bobenzoates are to be preferred to monobenzoates. It is discussed, that the reaction behaviour of oxy anions in GTP can also be understood on the basis of enolate anions as active polymerization species.
Polysiloxane‐Containing triblock copolymers via cationic ring‐opening polymerization of cyclic siloxanes
Authors: Mougin N. , Rempp P. , Gnanou Y. 
Published: April 2003

AbstractA novel original method allowing the synthesis of polydimethylsiloxane (PDMS)‐containing triblock copolymers is described. The synthetical procedure is based on the use of ω‐silyl triflate‐terminated polymers serving as macroinitiators for cyclic siloxane polymerization. Due to the continous interchange reactions between the siloxane linkages and the reactive cationic sites, triblock copolymers are obtained. This method was applied to the synthesis of triblock copolymers with a central PDMS block and either two polystyrene or two poly(ε‐caprolactam) rigid external blocks. Another method, the well‐known “end‐blocker” technique, was unsuccessful for obtaining block copolymers.
Synthesis and characterization of processable aromatic poly(azomethine)s with ether linkages
Authors: Yeakel Craig , Gower Karmen , Mani Rajarathnam S. 
Published: April 2003

AbstractHigh‐molecular‐weight polyketanils with flexible ether linkages were prepared by the reactions of N,N′‐bis[α(4‐fluorophenyl)benzylidene]‐1,4‐benzenediamine with phenoxides derived from several less acidic diphenols. Molecular sieves medicated reactions of 1,4‐benzenediamine with two equivalents of 4‐flurobenzophenone afforded the desired monomer in good yield. Formation of successive ether linkages via nucleophilic aromatic substitution reactions constituted the polymerforming step. The high‐molecular‐weight polymers form tough films upon compression molding, exhibit relatively high glass transition temperatures and good thermal stability.
Poly(ester‐imide)s derived from 3,4,9,10‐perylenetetracarboxylic acid, ω‐aminododecanoic acid and α,ω‐alkanediols
Authors: Karayannidis George , Stamelos Demetris , Bikiaris Demetris 
Published: April 2003

AbstractA series of new poly(ester imide)s (PEI's, 6) was synthesized from 12, 12′‐(3,4: 9,10‐perylenetetracarboxdimido)didodecanoyl chloride (4) and various α,ω‐alkanediols (5). DSC measurements revealed for all PEI's a solid‐solid transition at ca. 190–200°C and a melting transition between 300–330°C. Neither a liquid‐crystalline phase not glass transition were detectable, suggesting the PEI's are highly crystalline. Heat distortion measurements showed that the crystallites form a coherent matrix and the amorphous phase is dispersed in the voids, which is quite different to other semicrystalline polymer. Decomposition started just above the melting and was completed at approx. 750–800°C.
Copolymers of substituted styrenes with vinylidene cyanide or methylvinylidene cyanide. 13C NMR studies of their microstructures
Authors: Monthéard Jean‐Pierre , Boinon Bernard , Belfkira Ahmed , Raihane Mustapha , Pham Q. T. 
Published: April 2003

AbstractVarious copolymers of vinylidene cyanide (1a) and methylvinylidene cyanide (1b) with substituted styrenes (2a–g) were synthesized by radical copolymerization, and their microstructures were studied by 13C NMR spectroscopy. The copolymers of vinylidene cyanide with substituted styrenes have a perfectly alternating structure, but the copolymers of methylvinylidene cyanide are rich in alternating structure and might contain a minor part of poly(substituted styrene) as blocks or as homopolymers. A distinction between the two possibilities was not possible.
Thermotropic liquid‐crystalline aromatic‐aliphatic polyimides, 2. Effect of aliphatic spacer lengths and polymer compositions on the liquid‐crystalline properties of poly(imide‐carbonate)s
Authors: Hirata Tomohiro , Sato Moriyuki , Mukaida Ken‐ichi 
Published: April 2003

AbstractNovel thermotropic liquid‐crystalline (LC) aromatic‐aliphatic poly(imide‐carbonate)s were prepared by melt polycondensation of N,N′‐bis(ω‐hydroxyalkyl)pyromellitdiimide and/or 6,6′‐(4,4′‐biphenylylenedioxy)dihexanol with hexamethylene bis(phenylcarbonate). The monomers, dihydroxyalkyl derivatives of pyromellitdiimide, were obtained by deacetylation of the intermediate diacetylated compounds with p‐toluenesulfonic acid. The intermediates were synthesized by condensation of pyromellitic dianhydride (PMDA) with ω‐aminoalcohols followed by cyclization with acetic anhydride. Most of the poly(imide‐carbonate)s obtained in high yields have high molecular weights and show very good solubilities in organic solvents. The structures of the resulting polymers were confirmed by FT/IR and NMR spectroscopy measurements and elemental analyses. Thermotropic LC properties of the polymers were evaluated by differential scanning calorimetry (DSC), polarizing microscopy and powder X‐ray analyses. These measurements suggested that only biphenyl unit‐rich copolymers and polymers with shorter spacers next to the imide ring, which favor the orientation of the imide ring and the polymer chains, form nematic LC mesophases. The glass transition temperatures (Tg) and the LC phase transition temperatures tend to decrease with increasing imide‐neighboring aliphatic spacer lengths.
Static and dynamic light scattering studies of dextran from leuconostoc mesenteroides in the dilute region
Authors: Nordmeier Eckhard , Xing Hai , Lechner Manfred‐Dieter 
Published: April 2003

AbstractDextrans with mass‐average molar masses 8.104 g/mol ⩽ M̄w ⩽ 108 g/mol have been studied in water by means of static and dynamic light scattering at different temperatures. Static light scattering (SLS) yields the z‐average mean‐square radius of gyration, 〈S2〉z and the second virial coefficient A2. It is found that the dependences of 〈S2〉 and A2 on the mass‐average molar mass, M̄w, can be well described by the power laws 〈S2〉 = KS · M̄ and A2 = KA · M̄. The exponent vs is independent of the temperature T, while vA decreases as T is raised. Dynamic light scattering (DLS) yields the apparent diffusion coefficient, Dapp (q,c), and the hydrodynamic radius, Rh, where q is the wave vector and c the polymer concentration. For small q, a plot of Dapp (q, c) versus q2 · 〈S2〉z gives a straight line. The intercept $ D_{\rm z} (c) = \mathop {\lim }\limits_{q \to 0} D_{{\rm app}} (q,c) $ represents the centre‐of‐mass translational diffusion coefficient. Its dependence on the concentration, c, can be well simulated by the relation \documentclass{article}\pagestyle{empty}\begin{document}$ D_{\rm z} (c) = D_{{\rm z,}0} \left[ {1 + k_{{\rm D},2} \cdot c} \right] $\end{document}. Here kD, 2 is the second hydrodynamic virial coefficient and Dz,0 the z‐average of the translational diffusion coefficient at infinite dilution. The analysis of the kD,2 ‐data shows that dextran molecules behave rather as interpenetrable than as non‐interpenetrable spheres. The density p = (3 M̄w)/(NA · 4 π R) proves to be a measure for the degree of penetration; p decreases with increasing M̄w, indicating that penetration becomes easier at higher molar masses.
Synthesis and polymerization of fluorinated acrylic monomers substituted in α‐position, 2. Synthesis and polymerization of 2‐perfluorohexylethyl α‐acetoxyacrylate
Authors: Bessiere Jean‐Marie , Boutevin Bernard , el Bachiri Abderrahim , el Harfi Ahmed 
Published: April 2003

AbstractThe synthesis of 2‐perfluorohexylethyl α‐acetoxyacrylate (b) H2CC(OAc)CO2C2H4C6F13 (1) was performed in two steps starting from pyruvic acid and 2‐perfluorohexylethanol (3,3,4,4,5,5,6,6,7,7,8,8,8‐tridecafluoro‐1‐octanol) with an overall yield of about 50%. Esterification of pyruvic acid with the adequate fluorinated alcohol was followed by enol acetylation to give monomer 1. Homopolymerization and copolymerization of 1 are easily carried out. From the kinetic study of the homopolymerization and copolymerization of 1 with styrene, the numerical values of the ratio square of the rate constant of propagation over the rate constant of termination k/kt and of the copolymerization reactivity ratios r1 and r2 of the two monomers were determined.
Ion pairs, cations and anions in ternary solutions of bis(polystyryl)magnesium and magnesium bromide in tetrahydrofuran
Authors: Jappens‐Loosen Pascale , Beylen Marcel Van , Huyskens Pierre 
Published: April 2003

AbstractA conductometric method is developed for the study of the ternary solutions in tetrahydrofuran of bis(polystyryl)magnesium (PStMgPSt) containing various proportions r of magnesium bromide. The concentration of bis(polystyryl)magnesium varies from 10−4 to 2.10−3 mol.dm−3, the ratio r from O to 17,4 and the temperature from +20°C down to −60°C. The addition of MgBr2 provokes the replacement of the ion pairs PStMgPSt by PStMgBr, the dismutation constant being at 20°C Kdism = 42 ± 2 with a molar enthalpy of − 5 ± 2 kJ.mol−1. The dismutation is chiefly ruled by a conjugated steric effect that lowers the stability of PStMgPSt. In this concentration range, aggregation of styryl ion pairs is negligible. Moreover for a given r the degree of dissociation of the polymer is independent of its concentration. This is due to the complete predominance in this concentration range of the triple anions Mg(PSt), MgBr(PSt) and MgBr2PSt−, approximately in the proportions of the ion pairs fpp, fbp and fbb as calculated from the dismutation constant. The triple anions MgBr are still completely negligible, as are also the triple cations. The single cations MgPSt+ and MgBr+ are approximately in the proportion fpp. Kdism/fbp, the latter are ones becoming predominant above r = 3.
Synthesis of poly(N‐tert‐butylaziridine)s with functional end‐groups
Authors: Christova Darina C. , Velichkova Rumiana S. , Panayotov Ivan M. 
Published: April 2003

AbstractPoly(N‐tert‐butylaziridine) (poly(TBA)) with hydroxy, amino, HOC(O)CHCHC(O)and P(O)(OCH3)2 end‐groups were synthesized via termination reactions of living poly(TBA) with appropriate nucleophiles. 2‐Aminoethanol, sodium 2‐aminoethylate, maleic anhydride and dimethyl phosphonate were used. The functionally terminated oligomers were of uniform size and with a functionally near one.
Conductivity and photoconductivity of undoped and doped Langmuir‐Blodgett films of a polymer with hexaalkoxytriphenylene side‐groups
Authors: Catry Christian , Van der Auweraer Mark , De Schryver Frans C. , Bengs Holger , Häussling Lucas , Karthaus Olaf , Ringsdorf Helmut 
Published: April 2003

AbstractLangmuir‐Blodgett films from a polymer with triphenylene moieties in the side groups deposited on a quartz substratum with aluminium and gold electrodes show a dark conductivity in the plane of the Langmuir‐Blodgett film. This dark conductivity is increased using gold electrodes as compared with aluminium electrodes. It depends in a superlinear way upon the applied electric field and is not enhanced by oxygen. The dark conductivity can be enhanced by doping the Langmuir‐Blodgett films with iodine but it is not influenced by doping the Langmuir‐Blodgett films with 2,4,7‐trinitro‐9‐fluorenone. Upon excitation in the absorption band of the triphenylene moiety an in‐plane photocurrent, which is enhanced by oxygen, could be observed. Also the photocurrent is enhanced by using gold electrodes. Doping the Langmuir‐Blodgett films with iodine or 2,4,7‐trinitro‐9‐fluorenone quenches the photocurrent. Up to 10 W/m2 the photocurrent depends linearly upon the intensity of the incident light.