bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of various proton traps on the bifunctional cationic polymerization of chloroethyl vinyl ether mediated by α‐iodo ether/zinc dichloride
Authors: Bennevault Véronique , Peruch Frédéric , Deffieux Alain 
Published: April 2003

AbstractThe synthesis of relatively high molar mass telechelic poly(chloroethyl vinyl ether)s (PCEVE) via bifunctional initiation of the “living” cationic polymerization of CEVE was examined in the absence and in the presence of various proton traps. In the absence of a proton trap, a monofunctional initiation involving hydrogen iodide (HI), formed by partial hydrolysis of trimethylsilyl iodide (TMSI) by adventitious water, occurred concurrently to the main bifunctional process. The addition of sterically hindered aromatic amines leads to complete inhibition of the polymerization due to the formation of a complex between the aromatic amines and ZnCl2. In the presence of trialkylaluminium as HI trapping agent, monofunctional initiation is totally suppressed and a clean bifunctional polymerization takes place. Telechelic PCEVE of DPn up to 300 with narrow molar mass distribution were synthesized. However, in the presence of these additives, a slow ligand exchange between AIR3 and ZnCl2 takes place, decreasing the rate of polymerization. For polymers with high DPn (>300), the increasing amount of trialkylaluminium required to totally suppress the formation of monofunctional polymer results in a chain coupling process during the deactivation step. This reaction limits the clean synthesis of high molar mass bifunctional PCEVE.
End‐group characterization of poly(methylphenylsilane) by alkali metal salts doped MALDI‐TOF mass spectra
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Puglisi Concetto , Samperi Filippo , Sepulchre Maurice 
Published: April 2003

AbstractThe end groups of a sample of poly(methylphenylsilane) (PMPS) obtained by the Wurtz coupling reaction of diorganodichlorosilane were characterized by MALDI‐TOF mass spectrometry. Three fractions were obtained by fractionation of a PMPS sample with methanol, in order to get information on the distribution of end groups as a function of the molecular weight. The MALDI mass spectra of these fractions showed well‐resolved signals up to 2500 Da corresponding to open chain oligomers of PMPS bearing four different types of end groups: Si(CH3)3, OSi(CH3)3, OCH3, H. Six different types of linear oligomers were identified together with a sizeable amount of cyclic oligomers, most likely generated during the polymerization step. The problem of isobar mass series in the MALDI spectra due to clusters of oligomers with Li+, Na+, K+ was solved by comparing the MALDI spectra of PMPS fractions with and without the addition of a specific alkaline salt (KCl or Nal) to the solution containing the sample and matrix. The intensity of the oligomer clusters with the specific cation were enhanced with respect to the others. The mass shifts observed in the MALDI‐TOF doped spectra with respect to the undoped ones allowed the unambiguous assignments of the isobar peaks corresponding to PMPS oligomers.
Polyanhydrides, 7. Soluble polyanhydrides derived from isophthalic acid, 4‐hydroxybenzoic acid and various diphenols
Authors: Kricheldorf Hans R. , Jürgens Claas 
Published: April 2003

AbstractOne series of poly(ester‐anhydride)s, PEAs, was prepared by polycondensation of isophthaloyl chloride with mixtures of silylated 4‐hydroxybenzoic acid and various dihydroxy‐substituted naphthalenes. Most of these PEAs are semicrystalline materials with glass transition temperatures (Tg) in the range of 130−190°C and melting temperatures (Tm) in the range of 220−350°C. In a second series of PEAs, phenylhydroquinone, bisphenol‐A and 3,3′‐dimethylbisphenol‐A were used as diphenols. All but one PEA of the second series are amorphous materials with good solubility in chloroform and other organic solvents. GPC measurements indicated viscosity‐average molecular weights (M̄v) up to 38 000.
Synthesis and free radical polymerization of p‐methylseleno‐ and p‐phenylselenostyrenes
Authors: Ando Tsugumichi , Kwon Tae Seok , Kitagawa Akiko , Tanemura Takahiro , Kondo Shuji , Kunisada Hideo , Yuki Yasuo 
Published: April 2003

Abstractp‐Methylselenostyrene (1) and p‐phenylselenostyrene (2) as selenium‐containing vinyl monomers were prepared. Both monomers are readily polymerized free radically to afford the corresponding polymers having molecular weight of about 20 000 ∼ 150 000. These homopolymers are stable below 300°C. From the copolymerization with styrene, Q values of 1 and 2 were calculated to be 1,18 and 1,03, respectively. On the other hand, e values of these monomers are −0,24 and −0,04, respectively, indicating the electron withdrawing character of the seleno groups.
The effect of alkyl chain length of amphiphilic phospholipid polyurethanes on haemocompatibilities
Authors: Li Yu‐Jun , Bahulekar Raman , Chen Tian‐Ming , Wang Yan‐Feng , Kodama Makoto , Nakaya Tadao 
Published: April 2003

AbstractA series of phospholipid diols based on different lengths of alkyl chains such as eicosyl, stearyl, cetyl, lauryl, octyl, and butyl was synthesized and characterized. The phospholipid diols were subjected a polyaddition polymerization with hexamethylene diisocyanate. The haemocompatibilities of the resulting phospholipid polyurethanes were evaluated by platelet rich plasma contacting experiments and viewed by scanning electron microscopy. The polymers with alkyl chains of 20, 18, 16, and 12 carbon atoms showed much better haemocompatibilities than those with alkyl chains of 8 and 4 carbon atoms.
Chirality induction in cyclopolymerization, 5. Template effect of chiral acyclic 1,2‐glycols on the cyclo‐copolymerizations of (S)‐1,2‐propanediyl and (2S,3S)‐2,3‐butanediyl bis(4‐vinylbenzoate)s with styrene
Authors: Kakuchi Toyoji , Haba Osamu , Uesaka Takahiro , Yamauchi Yukio , Obata Makoto , Morimoto Yasushi , Yokota Kazuaki 
Published: April 2003

AbstractThe copolymerizations of (S)‐1,2‐propanediyl and (2S,3S)‐2,3‐butanediyl bis(4‐vinyl‐benzoate)s (2a and 2b) (M1) with styrene (M2) were carried out using 2,2′‐azoisobutyronitrile in toluene at 60 °C. For the cyclocopolymer 3, the extent of cyclization of 3b is higher than that of 3a. The monomer reactivity ratios are r1 = 8.34 and r2 = 0.27 for 2a and r1 = 6.82 and r2 = 0.19 for 2b. The specific rotation ([α] in deg · dm−1 · g−1 · cm3 c = 1.0 g · dL−1; CHCl3) changes from +230 to +176 for 3a and from +319 to +150 for 3b. After removing the chiral templates, the resulting poly[(methyl 4‐vinylbenzoate)‐co‐styrene]s showed a specific rotation ([α] in deg · dm−1 · g−1 · cm3 c = 1.0 g · dL−1; CHCl3) of −2 for 4a and of −8 for 4b, indicating that the (2S,3S)‐2,3‐butanediyl template shows a higher ability to cause asymmetric induction by comparison with the (S)‐1,2‐propanediyl one. A split Cotton effect due to the positive chirality was observed in the CD spectrum of 2 and the reversed one for 4. According to the CD exciton chirality method, the clockwise‐twist of two 4‐vinylbenzoate for 2 transmitted its chirality to 4 in which two 4‐vinylbenzoyl groups are twisted counterclockwise, i. e., an (R,R)‐configuration of vicinal (methyl 4‐vinylbenzoate) units in the main chain.
Copolymerization of ethylene and styrene with monocyclopentadienyltitanium trichloride/methylalumoxane catalyst
Authors: Oliva Leone , Mazza Stefano , Longo Pasquale 
Published: April 2003

AbstractA series of ethylene‐styrene copolymerizations was carried out in the presence of cyclopentadienyltitanium trichloride and methylalumoxane at 20°C and at different comonomer feed compositions. By sequential extraction a copolymeric material with a styrene units content up to 36 mol‐% can be separated from the homopolymeric products. Some considerations about the relative reactivity of the comonomers and the regioregularity of the styrene insertion are made on the basis of the 13C NMR spectra.
Novel sulfur‐containing ferrocene polymers
Authors: Nuyken Oskar , Pöhlmann Thomas , Herberhold Max 
Published: April 2003

AbstractFerrocene‐containing polymers were synthesized via addition reaction of 1,1′‐dimercaptoferrocene (1) and 1,1′‐bis(2‐mercaptoethyl)ferrocene (2) to various diolefinic monomers such as dimethacrylates, divinyl ethers, divinyl sulfones and others. The dithiol 1 was also used as a monomer in condensation reactions with bifunctional acid chlorides. The polymerization of propylene sulfide in the presence of 1 as a bifunctional initiator was found to lead to polymers with a single central ferrocene unit.
A new methodology for studying multiple‐site‐type catalysts for the copolymerization of olefins
Authors: Soares J. B. P. , Abbott R. F. , Willis J. N. , Liu X. 
Published: April 2003

AbstractA novel methodology is presented for studying the nature of multiple‐site‐type catalysts used for the synthesis of olefin copolymers. Experimental results of copolymer composition (short‐chain branching) versus molecular weight are obtained by analyzing high‐temperature gel‐permeation chromatography fractions with Fourier‐transform infrared spectroscopy. The molecular weight distribution obtained by gel‐permeation chromatography is deconvoluted to determine the number of different site types on the catalyst. The average copolymer composition of chains made on each site type is then determined from copolymer composition versus molecular weight data. It is also shown how to extend this methodology to determine the comonomer reactivity ratios per site type.
Acylation of (partially) silylated poly(vinyl alcohol)s with acyl chlorides. Vinyl chloride/vinyl ester copolymers by polymer analogous reaction
Authors: Mormann Werner , Wagner Thomas 
Published: April 2003

AbstractAcylation of (partially) silylated poly(vinyl alcohol) with acyl chlorides and anhydrides was investigated under different conditions. In the presence of an acid acceptor (triethylamine) at temperatures below 50°C selective acylation of hydroxy groups was observed in agreement with literature data. At elevated temperature (160°C) without the use of an acid acceptor hydroxy and trimethylsiloxy groups react in an unselective manner. In addition, significant amounts of chlorine were found in the resulting polymers under these conditions, though no double bonds were detected. A polymer analogous reaction without incorporated chlorine was achieved with benzoic anhydride as acylating agent. Random distribution of chlorine and benzoyloxy groups most likely is obtained.
Third‐order nonlinear optical properties of poly(1,4‐vinylenephenylene) and its derivatives
Authors: Shim Hong‐Ku , Lee Kwang Sup , Jin Jung‐Il 
Published: April 2003

AbstractPoly(1,4‐phenylenevinylene) (PPV) and its derivatives are readily processable and thermally stable polyconjugated polymers. Since PPV contains phenylene units, its structure can be easily altered and modified in the electronic structure. Moreover, PPV and the derivatives are easily prepared via water‐soluble or organic‐soluble precursor polymers. Various PPVs substituted with electron‐donating or ‐withdrawing groups were synthesized and their third‐order optical nonlinearities were investigated by third‐harmonic generation method or degenerate four‐wave mixing technique. When phenylene rings carry two alkoxy electron‐donating groups, the substituted PPVs show third‐order nonlinear optical properties up to an χ(3) value of about 10−9 esu. In order to obtain polymeric materials having high optical quality, PPV and silica alkoxide can be mixed successfully by sol‐gel processing without any phase separation or precipitation. This unusual organic‐inorganic hybrid shows a great advantage in the photonics applications.
Characterization of the differences in the crystallinity from surface to bulk of compression‐molded polypropene sheets using attenuated total reflection fourier‐transform IR spectroscopy
Authors: Kawamoto Naoshi , Mori Hideharu , Nitta Koh‐hei , Yui Nobuhiko , Terano Minoru 
Published: April 2003

AbstractThe crystallinities of compression‐molded polypropene sheets were investigated by applying Fourier‐transform (FT)‐IR and attenuated total reflection (ATR) FT‐IR analyses. Two internal reflection elements, Ge and KRS‐5, with an angle of incidence of 45°, were used to obtain the depth profiles of the crystallinity of polypropene sheets from the surface to bulk. The crystallinity in the region from the surface to about 0,7 μm depth was considerably lower than that in bulk. Polypropene sheets with higher comonomer content showed the same tendency, which was enhanced with decreasing molding temperature.
Drawn gel films of blends of ultrahigh‐molecular‐weight polyethylenes and low‐molecular‐weight short‐chain branched polyethylene
Authors: Yeh Jen‐taut , Lin Yu‐lang , Fan‐Chiang Chien‐cheng 
Published: April 2003

AbstractA critical concentration was found for different compositions of UHMWPE/SBPE solutions, at which the concentration dependence of the reduced viscosity changes from low to high power. The critical concentration (Cc) is shifted to a higher value with increasing amount of SBPE in the UHMWPE/SBPE gel. The birefringence of the drawn films suggests that the degree of orientation of UHMWPE molecules along the drawing direction increases with the draw ratio. The increased orientation of UHMWPE improves the tensile strength and moduli of the drawn films. The draw ratios of gel films prepared from each blend of UHMWPE and SBPE exhibits a maximum value when the samples were prepared at concentrations close to their critical concentration. On the other hand, the maximum draw ratio obtained for gel films prepared near their Cc decreases significantly at higher weight ratios of SBPE to UHMWPE. In contrast, the gel films with less than 2 wt.‐% of SBPE in UHMWPE yield a higher maximum draw ratio than the sample prepared from pure UHMWPE gel. Possible mechanisms accounting for this behavior are proposed.
Polymerization of methacrylic acid esters with the aged system of lanthanum versatate and p‐chlorobenzenediazonium tetrafluoroborate
Authors: Sato Tsuneyuki , Naruse Motokazu , Toyosu Kentaro , Seno Makiko 
Published: April 2003

AbstractThe aged system of lanthanum versatate (1) and p‐chlorobenzenediazonium tetrafluoroborate (2) was found to initiate effectively the radical polymerization of acrylic monomers including alkyl methacrylates, butyl acrylate and acrylonitrile, although its initiating activity is lower than that of the non‐aged system. The polymerization of methyl methacrylate (3) with the aged 1/2 system was studied kinetically in acetone. The initial polymerization rate (Rp) is expressed by Rp = Kċ[aged 1/2]0.80 ċ [3]1.1 at 50°C. The overall activation energy of the polymerization is 59.0 kJ ċ mol−1. The molecular weight of the resulting poly(3) formed in the early stage increases with increasing conversion. The polymerization system involves a persistent radical showing a four‐line EPR spectrum with a g‐value of 2.004. A three‐line spectrum due to the nitroxyl radical was also observed at lower monomer concentrations. The total concentration of persistent radicals was found to correspond well to the instantaneous polymerization rate. The copolymerization of styrene (M1) and 3 (M2) with the aged initiator system was examined at 50°C in acetone. r1 and r2 are 0.19 and 0.47, respectively. The former is considerably smaller than that (0.52) reported for the conventional radical polymerization.
Polyelectrolyte complexes obtained by radical polymerization in the presence of chitosan
Authors: Cerrai Piero , Guerra Giulio D. , Tricoli Mario , Maltinti Simona , Barbani Niccoletta , Petarca Luigi 
Published: April 2003

AbstractThe radical polymerization of acrylic acid and sodium 4‐styrenesulfonate in the presence of chitosan as a template gives insoluble products, identified as the polyelectrolyte complexes chitosan‐poly(acrylic acid) and chitosan‐poly(4‐styrenesulfonate). Kinetic results do not permit to propose any mechanism in the first case, while suggest a “pick‐up” one in the second. The polyelectrolyte complexes have been characterized by FT‐IR spectroscopy, X‐ray diffractometry, optical and scanning electron microscopies, differential scanning calorimetry and thermogravimetric analysis. The results obtained indicate an ordered structure for the first complex, while the second one appears similar to that obtained by reacting the parent polymers. Therefore, the template polymerization technique appears advantageous only for the synthesis of the chitosan‐poly(acrylic acid) complex. The thermal analysis shows that the complexes undergo two successive modifications on heating. FT‐IR analysis demonstrates that the first process is an esterification between the hydroxyls of chitosan and the acidic groups of both daughter polymers; the second one appears to be an amidation of the chitosan ammonium groups only with the sulfonate groups.
Polymerization of ethylene oxide using yttrium isopropoxide
Authors: Choi Young K. , Stevels Willem M. , Ankoné Marc J. K. , Dijkstra Pieter J. , Kim Sung W. , Feijen Jan 
Published: April 2003

AbstractWell defined poly(ethylene oxide)s were prepared using yttrium isopropoxide as an initiator. End group analysis using 1H‐ and 13C NMR spectroscopy revealed that only polymers with isopropyl ether and hydroxyl end groups were produced. The molecular weight is controlled by the initial amount of initiator added and low polydispersity polymer (Mw/Mn ≈ 1.1) was isolated. Sequential polymerization indicated the suitability of this initiator for macromolecular engineering.
Polymer microspheres prepared with a macroinitiator, 2. Sugar balls from 2‐methacryloyloxyethyl‐D‐glucopyranoside
Authors: Kitano Hiromi , Kawabata Junko , Muramoto Tadashi 
Published: April 2003

AbstractMacroinitiator was prepared by the coupling of the disuccinimidyl ester of 4,4′‐azobis(cyanovaleric acid) with poly(methacryloyloxyethyl‐D‐glucopyranoside) (PMEGlc) with an amino group at its end. Styrene and divinylbenzene were copolymerized using the initiator in the presence of sodium dodecylsulfate. The polymer microspheres obtained have PMEGlc chains on their surfaces (“sugar balls”). Aggregation phenomena were observed when a solution of lectin (Con‐A) was added to the suspension, due to a specific recognition of sugar residues on the microsphere by a tetrameric lectin molecule. A suspension of sugar balls could not be flocculated even upon addition of an aqueous 3M NaCl solution due to the thick diffuse layer composed of PMEGlc chains on their surfaces. The utility of macroinitiators to prepare various polymer materials which have biomedical functions on their surfaces is suggested.
A kinetic study of free‐radical copolymerization of butyl acrylate with methyl methacrylate in solution
Authors: Madruga Enrique López , Fernández‐García Marta 
Published: April 2003

AbstractFree‐radical copolymerization at 50°C of butyl acrylate with methyl methacrylate was carried out in benzene solution using 3 and 5 mol/L as the overall concentration of monomers. Both the reactivity ratios and the rate coefficients of copolymerization are affected by the total monomer concentration. Reactivity ratios were analyzed on the basis of the “bootstrap” model, and the copolymerization rate is interpreted assuming a penultimate effect upon the propagation reaction.
Estimation of the conformational characteristics of polyurethane chains
Authors: Kašpárková Věra , Šimek Lubomír , Bohdanecký Miloslav 
Published: April 2003

AbstractLinear polyurethanes (PUR‐Dk) were prepared by reacting 4,4′‐methylenediphenyl diisocyanate (MDI) with low‐molecular‐weight diols HO(CH2)kOH (k = 2, 3, 4, and 6) and fractionated by precipitation or extraction with mixtures of N,N‐dimethylformamide (DMF) and dibutyl ether (DBE). The fractions were characterized by their weight‐average molecular weights Mw (light scattering) and intrinsic viscosities [η] in DMF (good solvent) and mixtures of DMF with DBE (poor solvents). The Kuhn statistical segment length lK was evaluated from the intrinsic viscosities in poor solvents. Low values of lK, (12 to 14) × 10−8 cm, indicate that benzene rings and virtual double bonds (urethane groups) confine neighbour interactions to bonds within the repeating units and assure independent rotations at the bonds adjoining them.
Thermodynamics of polymer blends based on poly(methyl acrylate) and poly(vinyl acetate) with different molecular weights
Authors: Casarino Piera , Brunacci Antonio , Pedemonte Enrico 
Published: April 2003

AbstractIn this work a study on thermodynamics of polymer blends, based on poly(methyl acrylate) (PMA) and poly(vinyl acetate) (PVAc), was carried out. Our foremost aim was to examine the molecular weight effect on polymer compatibility. The results confirm our hypothesis: the interaction parameter χ12, varies abruptly in a very restricted molecular weight range. In this way, it can be concluded that molecular weight, as well as other parameters (i.e. lateral group hindrance, chain functionalization, composition temperature and so on), influences greatly polymer miscibility.
Synthesis and photoconductivity study of polystyrene‐fullerene
Authors: Wang Changchun , Pan Baorong , Fu Shoukuan , Jiang Kejian , Chen Hongzheng , Wang Mang 
Published: April 2003

AbstractAn anionic polymerization process was adopted to synthesize polymeric fullerene (C60) derivatives. Ultraviolet/visible spectroscopy, differential scanning calorimetry and gel‐permeation chromatography demonstrate that C60 is chemically bonded to polystyrene, and that it is mainly bis‐substituted. The polystyrene‐C60 derivatives are soluble in a variety of solvents, such as tetrahydrofuran, toluene, trichloromethane. The material exerts good photoconductivity.
Synthesis and ring‐opening polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate; a comparison with the polymerization of 2,2‐dimethyltrimethylene carbonate
Authors: Weilandt Karl D. , Keul Helmut , Höcker Hartwig 
Published: April 2003

AbstractThe polymerization of 2‐acetoxymethyl‐2‐alkyltrimethylene carbonates (alkyl = methyl: AMTC, alkyl = ethyl: AETC) and of 2‐methoxycarbonyl‐2‐methyltrimethylene carbonate (MMTC) in toluene with sec‐butyllithium as initiator results in the respective polymer with yields between 78% and 88%. The analysis of the polymer microstructure by means of NMR spectroscopy reveals linear chains without branching due to an attack of the active chain end at the ester moiety of the repeating units. Poly(MMTC) and poly(‐AETC) afford crystalline materials upon precipitation from solution while poly‐(AMTC) is amorphous; after quenching from the melt all materials are amorphous. Copolymerization of AMTC, AETC and MMTC with 2,2‐dimethyltrimethylene carbonate (DTC) results in random copolymers. The kinetics of the polymerization of AETC and MMTC revealed that the ester side chain enhances the rate of propagation compared to the polymerization of DTC. The apparent rate constants of propagation in toluene with lithium alcoholate as active sites at 23°C were determined to be kappDTC = 4 ċ 10−3 s−1, kappAETC = 4,28 ċ 10−2 s−1, and kappMMTC = 2,57 ċ 10−2 s−1. Studies of ring‐chain equilibria in solution of tetrahydrofuran revealed that on the basis of the theory of Jacobson‐Stockmayer the characteristic ratios of the polymers are C∞PDTC = 7,1, C∞PMMTC = 8,6, C∞PAETC = 9,9, and C∞PAMTC = 13,4.