bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of polymers containing pseudohalide groups by cationic polymerization 4. Cocatalysis as a direct route to end‐capped poly(2‐methylpropene) with pseudohalide groups
Authors: Cheradame Hervé , Habimana Jean de la Croix , Chen Frank J. 
Published: April 2003

AbstractThe possibility to functionalize poly(2‐methylpropene) (PIB) by direct synthesis with functions containing nitrogen derived from the group of pseudohalogens, is demonstrated. Polymerization by cationic polyaddition of 2‐methylpropene using a suitable cocatalyst, here hydrazoic acid HN3 or hydrocyanic acid HCN, in the presence of titanium tetrachloride is carried out in methylene dichloride. The highest functionalization efficiency (f = 0,7) is obtained for a mole ratio catalyst‐to‐cocatalyst close to one. Part of the macromolecules is found to contain twice as many tert‐butyl groups as internal unsaturations. This finding is explained by the occurrence of some dimerization of macromonomers, which are formed by a PIB backbone terminated by one disubstituted unsaturation.
Observation of a nematic phase displayed by a polysiloxane with trinitrofluorenones as side groups
Authors: Möller Manfred , Tsukruk Vladimir V. , Wendling Jürgen , Wendorff Joachim H. , Bengs Holger , Ringsdorf Helmut 
Published: April 2003

AbstractThe synthesis and the results of the structural study of two copolysiloxanes with laterally fixed trinitrofluorenone (TNF) units is reported. The two copolysiloxanes having 2,4 (1a) and 5,3 (1b) dimethylsiloxane comonomer units per TNF side group differ significantly in their phase behaviour as evident from optical microscopy, differential scanning calorimetry and X‐ray scattering: 1b shows a nematic mesophase whereas 1a is an amorphous material. The different phase behaviour is discussed in terms of microphase separation between the siloxane backbone and TNF side groups.
High‐conversion emulsion polymerization
Authors: Maxwell Ian A. , Verdurmen Edwin M. F. J. , German Anton L. 
Published: April 2003

AbstractThe four important factors that determine the rate of emulsion polymerization are the propagation rate coefficient, the latex‐particle concentration, the monomer concentration in the latex particles, and the free‐radical concentration in the latex particles. Both theoretical considerations and experimental evidence suggest that the important factors that may reduce the rate of emulsion polymerization at high conversion are the propagation rate coefficient and the monomer concentration in the latex particles, and not the free‐radical concentration in the latex particle, if the initiator is not depleted. Various approaches for increasing the rate of emulsion polymerization at high conversion are suggested.
Synthesis of biodegradable polyesteramides with pendant functional groups
Authors: in't Veld Peter J. A. , Dijkstra Pieter J. , Feijen Jan 
Published: April 2003

AbstractMorpholine‐2,5‐dione derivatives having substituents with benzyl‐protected carboxylic acid, benzyloxycarbonyl‐protected amine and p‐methoxy‐protected thiol groups, respectively, were prepared in 29–58% yield by cyclization of the corresponding N‐[(2RS)‐bromopropionyl]‐L‐amino acids. Polyesteramides with protected pendant functional groups were obtained by ring‐opening copolymerization of either ϵ‐caprolactone or DL‐lactide with morpholine‐2,5‐dione derivatives having protected functional substituents. The copolymerizations were carried out in the bulk at 130°C using stannous octoate as an initiator and using low mole fractions (0,05, 0,10 and 0,20) of morpholine‐2,5‐dione derivatives in the feed. The molecular weight of the resulting copolymers ranged from 1,4 to 8,3 · 104. The ring‐opening homopolymerization of morpho‐line‐2,5‐dione derivatives with protected functional substituents was not successful. Polyesteramides with either pendant carboxylic acid groups or pendant amine groups were prepared by catalytic hydrogenation of the corresponding protected copolymers. Treatment of copolymers having pendant p‐methoxybenzyl‐protected thiol groups with trifluoromethanesulfonic acid resulted not only in the removal of the p‐methoxybenzyl group but also in severe degradation of the copolymers, due to acidolysis of main‐chain ester bonds.
Preparation and catalytic action of an asymmetric ethylene/vinyl alcohol copolymer‐copper complex membrane
Authors: Miyata Takashi , Yoshida Naoto , Nakamae Katsuhiko 
Published: April 2003

AbstractAn ethylene/vinyl alcohol copolymer (EVA)‐copper complex membrane was prepared by casting an EVA‐CuCl2 mixture (solvent: water‐propanol (1:1 v/v) mixture) on a polyethylene substrate and then immersing it in 0,1 M KOH aqueous solution. In the membrane, Cu was distributed asymmetrically in the direction of the membrane cross section. The distribution of Cu could be controlled by the temperature during preparation. The oxidation of hydroquinone during permeation through the complex membrane was performed using membranes with different Cu distribution. This distribution influences the permeation reaction. These results are well reproduced by a relation composed of Fick's law and Michaelis‐Menten type reaction kinetics. Therefore, a good reactor can be developed by controlling the catalyst distribution.
Synthesis of carboxy‐ and chloro‐terminated poly(propylene)s using Zn(C2H5)2 as chain transfer reagent
Authors: Shiono Takeshi , Kurosawa Hiroki , Soga Kazuo 
Published: April 2003

AbstractPropene was polymerized with conventional and Solvay‐type TiCl3 combined with Al(C2H5)2Cl using Zn(C2H5)2 as a chain transfer reagent. The produced terminal Zn‐carbon bonds of the polymer were reacted with carbon dioxide and chlorine in the presence of N‐methylimidazole followed by hydrolysis to obtain terminally carboxylated and chlorinated poly(propylene) in approximately 50% yield.
Derivatization of hydroxyl into α‐chloro ether: application to the synthesis of block copolymers from hydroxy‐telechelic polymers
Authors: Cramail Henri , Deffieux Alain 
Published: April 2003

AbstractIt has been recently shown that a‐halogeno ether, when activated by a weak Lewis acid such as ZnX2, may be used as initiator for the living cationic polymerization of vinyl ethers. A route to the a‐halogeno ether function is the action of dry hydrogen halide on an alcohol in the presence of an aldehyde or a cyclic acetal. The quantitative preparation of α‐chloro ethers by this route, as well as the use of such compounds to initiate the “living” cationic polymerization of vinyl ethers, was examined. This procedure was then applied to hydroxy‐telechelic polybutadiene to give a macro‐initiator with α‐chloro ether terminal groups. The latter was used to initiate the polymerization of vinyl ethers. The synthesis of poly(butadiene‐block‐ethyl vinyl ether) and poly(butadiene‐block‐2‐chloroethyl vinyl ether) is reported, as well as the preparation of other copolymers by chemical modification of the chloroethyl vinyl ether units.
Spontaneous polymerization of amphiphilic vinyl monomers, 1. Spontaneous polymerization of sodium dodecyl 2‐hydroxy‐3‐methacryloypropyl phosphate
Authors: Yasuda Yutaka , Rindo Katsuhiko , Aoki Shuzo 
Published: April 2003

AbstractSodium dodecyl 2‐hydroxy‐3‐methacryloyloxypropyl phosphate as an amphiphilic vinyl monomer was found to polymerize spontaneously without initiator in water. The polymerization takes place at a monomer concentration higher than the critical micelle concentration via a free‐radical mechanism, and complete conversion is achieved even at a very low initial monomer concentration (3 mmol/L) and a rather low temperature (35°C). In benzene, capable of forming inverse micelles, the polymerization also occurs spontaneously. In methanol, which gives an isotropic solution, the spontaneous polymerization proceeds only at high concentration (near 300 mmol/L). The 1H spin‐spin relaxation time (T*2) of the monomer changes discontinuously in a range of monomer concentration from 250 to 300 mmol/L in CD3OD, suggesting that some kind of monomer mutual interaction takes place in methanol too. Thus, it can be concluded that the micellar aggregation monomer molecules triggers the polymerization.
Synthesis of silicone macrocycles having a single functional side group by hydrosilylation under high dilution
Authors: Coqueret Xavier , Wegner Gerhard 
Published: April 2003

AbstractMacrocyclic poly(dimethylsiloxanes) (PDMS) having a single ester side group were prepared by coupling hydrosilane end‐groups of telechelic PDMS and olefinic functions of methyl 3,5‐diallyloxybenzoate under high‐dilution conditions. The theoretical and preparative aspects of the continuous‐flux technique that was used to perform the Pt‐catalyzed hydrosilylation reaction were examined in the light of the results of a previous kinetic study. Excessive amounts of catalyst, or high temperature, lead to the formation of colloidal Pt, the poor chemical selectivity of which is not acceptable. When the addition reaction is performed under conditions allowing homogeneous catalysis, the reaction takes place with a steady‐state concentration in reactive groups as low as 2 · 10−3−4 · 10−3 mol/L over periods as long as 24–36 h. the isolation of the monofunctional cyclic products by semi‐preparative size‐exclusion chromatography techniques from the linear condensation products and from more complicated multifunctional cycles is possible if the starting telechelic PDMS is of narrow molecular weight distribution.
Polyurethane elastomer‐LiClO4 complexes as a polymeric solid electrolyte
Authors: Seki Miharu , Sato Kojiro , Yosomiya Ryutoku 
Published: April 2003

AbstractA polymeric solid electrolyte with high ionic conductivity was prepared by complexing a polyurethane elastomer with LiClO4. The ionic conductivity of these complexes increases proportional to the increase of the content of poly(tetramethylene oxide) component in the polyurethane elastomer and with increasing LiClO4 concentration, and reaches a value of 10−4 S/cm at 80°C for [LiClO4] = 1,20 mmol/g polymer. The polyurethane elastomer‐LiClO4 complex has good mechanical properties compared with poly(ethylene oxide)‐and poly(propylene oxide)‐based complexes.
Synthesis of two novel heparinizable polymeric materials starting from an ethylene/vinyl alcohol/vinyl acetate terpolymer
Authors: Barbucci Rolando , Benvenuti Manuela , Magnani Agnese , Tempesti Federica 
Published: April 2003

AbstractA partially hydrolyzed ethylene/vinyl acetate (EVA) copolymer was modified through the covalent binding of a heparin‐complexing polymer, in order to improve its blood compatibility. Two different heparinizable polymeric materials (EVAPA I and II) were obtained by a two‐step reaction between an ethylene/vinyl alcohol/vinyl acetate (EVALVA) terpolymer and a poly‐(amido‐amine) (N2LL) using either hexamethylene diisocyanate (HMDI) or 1,1'‐carbonyldimidazole (CDI) as bifunctional agents. EVALVA terpolymer was prepared by a homogeneous saponification process, and the percentage of hydrolysis was determined by an analytical method. EVAPA I and II syntheses were followed by FT‐IR/ATR (Fourier Transform Infrared/Attenuated Total Reflection) spectroscopy.
Synthesis and phase‐transfer catalytic activity of hydroxyl‐containing polyetheramines bound to soluble or insoluble polystyrenes
Authors: Kohno Yutaka , Ogawa Nobuyuki , Chung Kwang Bo , Fukuda Wakichi , Tomoi Masao 
Published: April 2003

AbstractSoluble or insoluble polystyrenes with hydroxyl‐containing polyetheramine structures were prepared by the reaction of linear or crosslinked polystyrenes containing haloalkyl, tosyloxyalkyl, or epoxy groups with bis(2‐(2‐hydroxyethoxy)ethyl)amine(ATEG). The soluble polystyrenes with ATEG residue afforded polymeric alkoxides by the reaction with aqueous NaOH or KOH under two‐phase conditions. The introduction of oxygen‐containing spacer chains between ATEG residue and the polymer backbone resulted in the formation of cryptand‐like alkoxides, in which the counter cations were bound by cooperative coordination of the oxygen donors in the ATEG residue and in the spacers. The soluble and insoluble polymers with ATEG residue exhibited high catalytic activity for the dehydrobromination of 2‐bromoethylbenzene with aqueous NaOH or KOH under two‐and three‐phase conditions, respectively. The extra coordination of the oxygen donors in the spacers resulted in increased catalytic activity.
Phase separation of liquid‐crystalline graft copolymers
Authors: Blankenhagel Marita , Springer Jürgen 
Published: April 2003

AbstractThe phase separation behavior of graft copolymers containing poly(methyl methacrylate) grafts attached to a side‐chain liquid‐crystalline backbone is described and examined with respect to the share and the length of the grafts. Only copolymers with a low PMMA content show microphase separation. An increasing PMMA content leads to a miscibility of the components.
Synthesis and characterization of some new photochromic side‐chain liquid‐crystalline polymers
Authors: Ruhmann Ralf , Zschuppe Veit , Dittmer Manfred , Wolff Dietmar 
Published: April 2003

AbstractThe synthesis and characterization of a series of liquid‐crystalline copolymethacrylates containing side chains with both azobenzene and benzanilide moieties is described. The phase behaviour of the polymers is discussed in dependence of their copolymer composition. The copolymers are suitable for optical investigations on the photochemical trans‐cis isomerization of the azo group.
Poly(2,6‐Dimethyl‐1,4‐Phenylene oxide)/crosslinked polystyrene semi‐interpenetrating networks: Synthesis and properties
Authors: Penco Maurizio , Villa Anna Maria , Gobbi Cristina , Pegoraro Mario , Silvestro Giuseppe Di , Higgins Julia S. 
Published: April 2003

AbstractSemi‐interpenetrating networks (semi‐IPN's) based on linear poly(phenylene ether)s and crosslinked polystyrene can be prepared by reactive moulding of crosslinkable polymeric mixtures. These materials show thermomechanical properties which strongly depend on both the ratio of the two polymeric matrices and the degree of crosslinking in the polystyrene network. Samples based on a 50/50 weight ratio of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/crosslinked polystyrene show glass transition temperatures (Tg) which are very dependent on the degree of crosslinking. It is therefore possible to obtain materials with desired Tg, ranging from the Tg of the corresponding linear blend to that of poly(2,6‐dimethyl‐1,4‐phenylene oxide) alone.
Recent developments in the field of micellar polymers
Authors: Anton Peter , Köberle Peter , Laschewsky André 
Published: April 2003

AbstractThis article describes recent achievements in the field of micellar polymers, or “polysoaps”. Taking advantage of zwitterionic model polymers, systematic variations of the molecular architecture have provided an improved understanding of the relationship between the molecular structure of the polymers and their key properties such as surface activity and solubilization capacity. Useful rules are established, which take into account much of the previous data in the literature.
Synthesis and characterization of poly(5‐alkyl‐2‐norbornene)s by cationic polymerization. Effect of alkyl substituent length on monomer reactivity, polymer structure and thermal properties
Authors: Sagane Toshihiro , Mizuno Akira 
Published: April 2003

AbstractCationic polymerizations of various 5‐alkyl‐2‐norbornenes (RNB, where RH, CH3, C2H5, C5H11, C7H15, and C10H21) were carried out by the AlEtCl2/tert‐butyl chloride catalyst system, and the effect of the length of the alkyl substituents on the monomer reactivity and polymerizability, polymer structure, and softening point (SP) were investigated. The introduction of an alkyl substituent into 5‐position of the norbornene ring remarkably reduces the monomer reactivity and polymerizability, although the length of alkyl group does not affect them. 13C NMR structural analysis of poly(RNB)'s revealed that not only the normal 5‐or 6‐alkyl‐2,3‐unit but also other structures such as 5‐ or 6‐alkyl‐2,7‐, 4‐alkyl‐3,6‐units, etc., are the most plausible structures for the repeating units. Furthermore, the existence of the 4‐alkyl‐3,6‐repeating unit and of the alkylidene type end‐group indicates the presence of an intermediate tertiary cation (5‐alkyl‐5‐norbornyl cation), which causes the low reactivity and polymerizability of the monomers. The SP of oligomers of equal molecular weight (DPn = 3–5) decreases in the following order: HNB, CH3NB,C2H5NB>C5H11NB>C7H15NB>C10H21NB. The effect the alkyl substituent length on the SP is discussed on the basis of the 13C spin‐lattice relaxation times (T1) for the carbons in the alkyl group.
Studies on chitosan 5. Reactivity of partially N‐acetylated chitosan in aqueous media
Authors: Aiba Sei‐ichi 
Published: April 2003

AbstractThe reactivity of the amino groups of partially N‐acetylated chitosans (PAC‐H) was investigated using cyanuryl dichloride, pyrocarbonates, activated ester, carbodiimide and epoxy‐activated polymethacrylamide beads. The maximal reactivity was attained at neutral pH in the cases of the reaction with a monomethoxypoly(ethylene glycol) succinimidyl succinate, and with isonicotinic acid mediated by a water‐soluble carbodiimide. On the contrary, the maximal reactivity was attained under weakly basic conditions in the cases of reactions with diethyl pyrocarbonate, dimethyl pyrocarbonate and cyanuryl dichloride. The highest amount of PAC‐H was immobilized on the surfaces of epoxy‐activated polymethacrylamide beads at weakly alkaline pH. From these results it was concluded that PAC‐H's are favorable for preparing randomly substituted derivatives and for immobilizing them on surfaces because their solutions are stable at neutral and alkaline pH in contrast to conventional chitosans. The structure of the products was analyzed by IR spectroscopy, and a method for estimating the degree of substitution by IR is proposed.
Polysilanes fonctionnels, 3. Synthèse d'α,ω‐bis(triméthylsilyl)oligo(méthylphénylsilane)s précurseurs des α,ω‐bis(triméthylsilyl)oligo(chlorométhyl‐silane)s. Charactérisation des heptaméthyl phényl‐2 trisilane et octaméthyl diphényl‐2,3 tétrasilane
Authors: Reyx Danièle , Martins José Manuel Natário , Campistron Irène , Noireaux Patrick 
Published: April 2003

AbstractLow‐molecular‐weight organosilane polymers were prepared by sodium coupling of dichloro‐methylphenylsilane (1) with chlorotrimethylsilane (2). Gel permeation chromatography (GPC), IR and NMR (1H, 13C and 29Si) analysis of the crude product (3) were performed and compared with those of the isolated first oligomers, trisilane (3a) and tetrasilane (3b). The GPC characteristics, especially high resolution ones, in accordance with the α,ω‐bis(trimethylsilyl)‐oligo(methylphenylsilane) structure are compared with those of hydrocarbon polymers. The relations of the NMR characteristics of the methylphenylsilanediyl unit with the position along the chain and the configuration of the diads are approached. Some spectroscopic indications of the secondary structure are discussed.
Azo‐dyes as labels and as photoisomerizable units in chiral polyisocyanates
Authors: Müller Manfred , Zentel Rudolf 
Published: April 2003

AbstractPolyisocyanates (nylon 1) with azochromophores in the side chains were prepared for the first time. For this purpose we have synthesized two new azo dyes containing isocyanato groups. The monomers were copolymerized with alkyl isocyanates to prepare chiral dye‐containing polyisocyanates. Optical rotatory dispersion and circular dichroism measurements support the helical polymer structure with predominantly one twist sense (due to the chiral side chains, P and M helices are diastereomeric). The completely reversible photochemical isomerization (trans to cis) of the azochromophores reaches high conversions (about 80%), but does not change the conformation of the main chain.
Photo and thermal oxidative polyrecombination of some captodative substituted methane derivatives
Authors: Tanaka Hitoshi , Tsunemine Naoki , Sato Tsuneyuki , Ota Tadatoshi 
Published: April 2003

AbstractPhoto and thermal polyrecombinations of some captodative substituted cyano‐, methoxycar‐bonyl‐, and phenylmethane derivatives were carried out using peroxides as oxidizing agents at room temperature and 130°C. Cyano‐substituted methane derivatives easily gave a polymer with a molecular weight of several thousands by both photo and thermal polyrecombinations. Especially, phenylacetonitrile afforded a polymer in good yield even under conditions at which diphenylmethane gave no polymer. Methyl methoxyacetate gave no polymer in the thermal reaction, but afforded a polymer when using high concentrations of an oxidizing agent in the photoreaction. 1H nuclear magnetic resonance and electron paramagnetic resonance spectra demonstrated the production of a polymer with a structure mainly consisting of 1,1‐disubstituted methylene units and the generation of a captodative substituted methyl radical in the reaction medium.
Regulation in free‐radical polymerization of vinyl acetate and synthesis of end‐group modified poly(vinyl alcohol)s
Authors: Sato Toshiaki , Okaya Takuji 
Published: April 2003

AbstractA kinetical investigation on the consumption of a chain transfer agent in the free‐radical polymerization of vinyl acetate (VAc) was carried out. A new method to control the degree of polymerization of poly(vinyl acetate) (PVAc) or poly(vinyl alcohol) (PVA) as well as the end group content by continuous addition of a chain transfer agent, whose chain transfer constant is much larger than unity such as thiol compounds, during the course of VAc polymerization was proposed. The method using 2‐mercaptoethanol was applied to the preparation of lowmolecular‐weight PVAc and PVA with M̄w/M̄n ≈ 2.
Factors affecting the role of SiO2 in MgCl2‐supported Ziegler‐Natta copolymerization catalysts
Authors: Wang Jian‐Guo , Pang De‐Ren , Cheng Xiao‐Tan , Huang Bao‐Tong 
Published: April 2003

AbstractThis paper describes the roles of silica (SiO2), the butoxy ligand (OBu) and ethyl benzoate (EB) on ethylene/1‐butene copolymerization with MgCl2/SiO2‐supported titanium catalysts. The distribution of SiO2 and of the elements Mg and Ti was observed by means of an energy‐dispersed X‐ray micronalyzer on a scanning electron microscope (SEM). An inversed Si/Mg ratio results, at invariant Ti/Mg ratio andOBu content, in higher catalyst efficiency and higher comonomer incorporation, with a correspondingly decreased crystallinity of the copolymers. Thus, the inert carrier SiO2 favors copolymerizability, as seen from the values of the reactivity ratios. The copolymer compositional distribution is also affected by the SiO2 content, as seen from the DSC curves of the copolymers. As to the copolymer morphology, addition of SiO2 makes the copolymer particles larger and more uniform.
Stability of helical conformation and reactivity of optically active poly(triphenylmethyl methacrylate) in solution
Authors: Hosoda Masahiro , Schönhausen Ursula , Pino Piero 
Published: April 2003

AbstractThe stability of the helical conformation in optically active poly(triphenylmethyl methacrylate) (PTrMA) was investigated by heating the polymer solutions at 100°C. The optical rotation slowly disappeared with time, and some preliminary experiments showed that this phenomenon is not due to a typical racemization process, as it is accompanied by a loss of triphenylmethyl (Tr) groups due to secondary reaction. Experimental results in the presence of methanol indicated that the decrease of optical activity occurs according to first‐order kinetics and qualitatively methyl triphenylmethyl ether was isolated from the final solution. In order to explain the above results, full characterization of copolymers obtained by interrupting the methanolysis at different conversions was performed. As a working hypothesis, it was assumed that the reaction starts at the end of the helices with a Tr‐oxygen bond fission and the reaction proceeds along the chain mainly with formation of block copolymers consisting of one block of PTrMA and one block of a probably random methacrylic acid anhydride/methacrylic acid copolymer.