bluuebunny/crossref_metadata_2025_split huggingface dataset:
The comppen model: A combined complex‐participation/penultimate effect model for free‐radical copolymerization
Authors: Brown Paul G. , Fujimori Kiyohisa 
Published: April 2003

AbstractThe Comppen model for the mechanism of free‐radical copolymerization has been developed to account for both penultimate effects and the participation of 1:1 electron donor‐acceptor complexes during chain propagation. This was achieved by incorporating penultimate effects into the existing complex participation model of Cais, Farmer, Hill, and O'Donnell, using probability theory to derive new copolymer composition and sequence distribution equations that are solely functions of the reactivity ratios, the composition of the comonomer feed, and the equilibrium constant for 1:1 electron donor‐acceptor complex formation. The model was applied to experimental data from styrene/maleic anhydride copolymers prepared in methyl ethyl ketone at 50°C over a wide range of comonomer feed compositions, using nonlinear least‐squares curve fitting techniques to determine best estimates of the reactivity ratios. Copolymer compositions and sequence distributions for copolymers in this comonomer system were then predicted using the Comppen model and compared to those determined experimentally via 13C‐NMR spectroscopy. © 1994 John Wiley & Sons, Inc.
Investigation on the particle growth mechanism in propylene polymerization with MgCl2‐supported ziegler–natta catalysts
Authors: Noristi L. , Marchetti E. , Baruzzi G. , Sgarzi P. 
Published: April 2003

AbstractTo elucidate the particle growth mechanism in propylene polymerization with high‐yield MgCl2‐supported Ziegler‐Natta catalysts, observations have been carried out by electron microscopy on a series of samples having different degrees of polymer growth (from 0.1 to 1000 g/g of catalyst). Topics such as surface and bulk morphology, catalyst fragmentation, as well as distribution of the catalyst residues in the polymer have been investigated. The experimental data suggest that if the site distribution in the catalyst is uniform and the polymerization conditions are mild, the polymer growth starts uniformly throughout the catalyst particle, which then undergoes an even and progressive fragmentation into very fine units homeogeneously dispersed in the polymer matrix. The above results thus provide further experimental support to the particle growth mechanism outlined in the multigrain or polymeric flow models. © 1994 John Wiley & Sons, Inc.
Phenylethynyl‐terminated imide oligomers and polymers therefrom
Authors: Hergenrother P. M. , Bryant R. G. , Jensen B. J. , Havens S. J. 
Published: April 2003

AbstractTwo new phenylethynyl endcapping compounds, 3‐ and 4‐amino‐4′‐phenylethynylbenzophenone, were synthesized and used to terminate imide oligomers from 3,4′‐oxydianiline and 4,4′‐oxydiphthalic anhydride at a calculated molecular weight of 9000 g/mol and from 3,4′‐oxydianiline (0.85 mol), 1,3‐bis (3‐aminophenoxy) benzene (0.15 mol), and 3,3′,4,4′‐biphenyltetracarboxylic dianhydride at a calculated molecular weight of 5000 g/mol. Glass transition temperatures for the cured oligomers were ∼ 249°C for the former and 272°C for the latter. Films cured at 350°C for 1 h were tough and flexible and provided high tensile properties. The uncured oligomers were readily compression molded to provide tough, solve nt‐resistant moldings. © 1994 John Wiley & Sons, Inc.
Synthesis of rigid polymer containing pendant norbornadiene moieties and its photochemical valence isomerization
Authors: Iizawa Takashi , Sueyoshi Tomoko , Hijikata Chikara , Nishikubo Tadatomi 
Published: April 2003

AbstractPolymers having pendant norbornadiene (NBD) moieties and rigid main chain were prepared from the reaction of partially brominated poly(2,6‐dimethyl‐p‐phenylene oxide) with a potassium carboxylate derivative of the corresponding NBD using a phase transfer catalyst in chlorobenzene. The photochemical valence isomerization of pendant NBD to quadricyclane (QC) moieties proceeded smoothly in the film state as well as polymer solution upon the irradiation by sunlight, xenon lamp, or high‐pressure mercury lamp. The rate of isomerization was affected by the structure of main chain in the polymer and the substituent groups of NBD derivatives. The catalytic reversion of the resulting QC moiety to the original NBD proceeded smoothly in the solution with (5,10,15,20‐tetraphenyl‐21H,23H‐por‐phine)cobalt(II) as the catalyst at room temperature; however, the reaction of NBD polymer containing poly(2,6‐dimethyl‐p‐phenylene oxide) (PPO) showed lower reactivity than that of the corresponding low molecular weight QC compound. When the cycle between the photochemical valence isomerization of NBD moiety to quadricyclane (QC) moiety and thermal reversion of QC moiety to NBD moiety at 160°C was repeated, the NBD polymer synthesized from PPO degraded gradually, whereas NBD polymer prepared from poly(4‐chloromethylstyrene) decomposed easily. Therefore, the rigid PPO structure showed high resistance for the degradation of NBD moiety. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of potentially biodegradable thermotropic polyesters based on p‐hydroxybenzoic acid and glycolic acid
Authors: Jin Xiaoming , Carfagna Cosimo , Nicolais Luigi , Lanzetta Rosa 
Published: April 2003

AbstractThe synthesis of novel thermotropic liquid crystalline copolyesters derived from aliphatic hydroxy acid (glycolic acid, GA) and aromatic hydroxy acid (p‐hydroxybenzoic acid, PHBA) via a melt‐copolycondensation process in the presence of various catalysts was explored. The following three possible routes were checked: PHBA and GA in different feed ratios with or without a catalyst; PHBA and GA in different feed ratios with or without a catalyst in the presence of acetic anhydride as a condensation agent; and different PHBA derivatives were used to examine the reactivity of aromatic hydroxy acid. The copolycondensability, chemical structure, liquid crystallinity, textures and morphology, phase transition behaviors and thermal stability, and solubility were investigated by FTIR, NMR, DSC, TGA, and polarized‐light microscope. It has been found that only the 60–70 mol % PHBA‐containing copolyesters could exhibit a nematic liquid crystallinity. The as‐prepared polymers were brittle due to relatively lower molecular weights. © 1994 John Wiley & Sons, Inc.
Solution polymerization of vinyl monomers in the presence of poly(N‐acetyliminoethylene) macroazoinitiators
Authors: Simionescu Cristofor I. , David Geta , Ioanid Aurelia , Paraschiv Vasile , Riess Gerard , Simionescu Bogdan C. 
Published: April 2003

AbstractNew block copolymers with poly(N‐acetyliminoethylene) and vinyl sequences were obtained by a two‐step synthetic approach. In the first stage macroinitiators of poly(N‐acetyliminoethylene) type, with azo groups inserted in the main chain, were prepared. They were latter used in the radical polymerization of some vinyl monomers [styrene, methacrylic acid, methyl methacrylate, butyl methacrylate, β‐(N‐carbazolyl)ethyl acrylate, β‐(methacryloyfoxy)ethyl 3,5‐dinitrobenzoate]. The resulting block copolymers were characterized by spectral methods, elemental analysis, gel permeation chromatography, and electron microscopy. The kinetic study of the thermal and photochemical decomposition of the synthesized macroazoinitiators, as well as the polymerization data, suggest a dependence of their initiating efficiency on the length of the poly(N‐acetyliminoethylene) segments. © 1994 John Wiley & Sons, Inc.
Chemical treatment of membranes of a polymer blend: Mechanism of the reaction of hypochlorite with poly(vinyl pyrrolidone)
Authors: Wienk I. M. , Meuleman E. E. B. , Borneman Z. , van den Boomgaard Th. , Smolders C. A. 
Published: April 2003

AbstractSodium hypochlorite solutions are used to treat membranes prepared from a polymeric blend containing poly(vinyl pyrrolidone) (PVP) to increase their water permeability. Sodium hypochlorite affects the membrane material in such a way that PVP is selectively removed from the membrane matrix. The mechanism of the reaction between hypochlorite and PVP is investigated by several chemical analysis techniques of the reaction products. Strong indications are found that the reaction involves chain scission of PVP according to a radical mechanism. © 1995 John Wiley & Sons, Inc.
Synthesis and properties of poly(phenylacetylenes) having o‐silylmethyl groups
Authors: Seki Hiroyuki , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractNovel phenylacetylene (PA) monomers, which have o‐silylmethyl groups of different bulkinesses, i.e., o‐Me3SiCH2PA, o‐Et3SiCH2PA, and o‐t‐BuMe2Si‐CH2PA, polymerized with W and Mo catalysts in high yields. The MoCl5‐Ph4Sn catalyst achieved the highest weight‐average molecular weights (Mw 7 × 105 − 12 × 105), and the Mw increased as the ortho‐substitutent became bulkier (e.g., Mw of o‐t‐BuMe2SiCH2PA: 12 × 105). These monomers polymerized in a living fashion by the MoOCl4‐n‐Bu4Sn‐EtOH catalyst. The resulting polymers were soluble in common solvents such as toluene and chloroform. In the UV‐visible spectra, a tendency was observed that absorption maxima shifted to longer wavelengths as the substituents became bulkier. Membranes of the polymers were fairly permeable to gases (e.g., oxygen permeability coefficients 30‐80 barrers). Though o‐(Me3Si)2CHPA also polymerized with W and Mo catalysts, the product polymer was partly insoluble in any solvent. © 1995 John Wiley & Sons, Inc.
Synthesis, structure, and thermal properties of epoxy‐imide resin cured by phosphorylated diamine
Authors: Chin Wei‐Kuo , Shau Min‐Da , Tsai Wei‐Chun 
Published: April 2003

AbstractNew phosphorylated epoxy‐imide polymer was obtained using diimide‐diepoxide (DIDE) cured with bis(3‐aminophenyl)methylphosphine oxide (BAMP). In addition, composition of the synthesized diimide‐diepoxide (DIDE) with common curing agents, e.g., 4,4′‐diaminodiphenylether (DDE) and 4,4′‐diaminodiphenylsulfone (DDS), were used for making a comparison of its curing reactivity, heat and flame retardation with that of bis(3‐aminophenyl)methylphosphine oxide. The reactivity of those curing agents toward epoxy‐imide, as measured by differential scanning calorimetry (DSC), was of the order DDE > BAMP > DDS. Through the evaluation of thermal gravimetric analysis (TGA), the new phosphorylated epoxy‐imide polymer demonstrated excellent thermal properties as well as a high char yield. © 1995 John Wiley & Sons, Inc.
Synthesis and crosslinking of cyano‐substituted polyamides and polyimides prepared from 1‐(2,2‐dicyano‐1‐hydroxyviyl)‐3,5‐diaminobenzene, sodium salt
Authors: Mikroyannidis John A. 
Published: April 2003

Abstract3,5‐Dinitrobenzoyl chloide was condensed with malononitrile in the presence of sodium hydroxide under phase‐transfer conditions to afford 1‐(2,2‐dicyano‐1‐hydroxyvinyl)‐3,5‐dinitrobenzene, sodium salt, which was catalytically hydrogenated to the corresponding diamine. The latter was used as starting material for the preparation of unsaturated cyanosubstituted polyamides and polyimides. The polymers were soluble in polar aprotic solvents, dilute sodium hydroxide, and certain strong inorganic and organic acids. Upon curing at 300°C for 65 h, crosslinked polymers were obtained that were stable up to 392–404°C in N2 or air and afforded an anaerobic char yield of 60–71% at 800°C. Their glass transition temperatures as determined by thermal mechanical analysis (TMA) were 221–275°C. © 1995 John Wiley & Sons, Inc.
Cyanate esters based on cardanol modified‐phenol‐formaldehyde resins: Syntheses and thermal characteristics
Authors: Nair C. P. Reghunadhan , Bindu R. L. , Joseph V. C. 
Published: April 2003

AbstractCardanol incorporated‐phenol‐formaldehyde novolac resins were synthesized by acid and base catalyzed reactions. The novolacs were transformed to their cyanate esters. The thermal cure characteristics of the cyanate esters depended upon the composition. The presence of cardanol proportionately facilitated the curing. The thermal characterization of the novolacs and the corresponding cured phenolic‐triazine networks indicated a dedicated a detremental effect of cardanol on the thermal stability and char residue of the resins. © 1995 John Wiley & Sons, Inc.
Study of bulk chain coupling reactions. III. Reaction between bisoxazolines or bisoxazlines and carboxy‐terminated oligomers
Authors: Douhi Abderrahim , Fradet Alain 
Published: April 2003

Abstract2,2′‐Bis(2‐oxazoline) and 2,2′‐bis[5,6‐dihydro‐(4H)‐1,3‐oxazine] have been used as chain coupling reagents (CC) and reacted in the bulk with α,ω‐dicarboxy‐poly(2,2′‐oxydiethylene adipate) (PS) or with α,ω‐dicarboxy‐polyamide 12 (PA). The reactions have been followed by viscosimetry, titration of COOH groups and 1H‐ and 13C‐NMR spectroscopy. Either with the PS/CC or PA/CC systems, or with the model system dodecanoic acid (DA)/CC, the reactions were fast, since in most cases 80% conversion was reached after 15 min reaction. The expected DA dimer or high molar mass PA or PS polymers were obtained. No significant side reaction has been detected. The thermal stability of the resulting polymers is higher than that of starting oligomers. Due to the introduction of CC units in the chains, the crystallinity of PA/CC is slower than that of starting PA. © 1995 John Wiley & Sons, Inc.
Studies on thermotropic liquid crystalline polyurethanes. II. Synthesis and properties of liquid crystalline polyurethane elastomers
Authors: Sun Shih‐Jieh , Hsu Keh‐Ying , Chang Teh‐Chou 
Published: April 2003

AbstractThree series of novel thermotropic liquid crystalline polyurethane elastomers (TLCPUEs) were studied. Hard segments were formed by using hexamethylene diisocyanate (HDI) reacted with a mesogenic unit, benzene‐1,4‐di(4‐iminophenoxy‐n‐hexanol), which also acted as a chain extender. Three diols: 1,10‐decanediol,poly(oxytetramethylene) glycol (PTMEG) Mn = 1000 and PTMEG Mn = 2000 were used as the soft segments. The effects of soft segments of polyurethanes on the liquid crystalline behavior were studied. Higher molecular weight TLCPUEs were obtained by adding 30−50 mol % of mesogenic segments to diisocyanates. In contrast to a conventional chain extender such as 1,2‐ethylene glycol or 1,4‐butyl glycol, the synthesized polyurethane elastomers exhibited a mesophase transition by using a mesogenic unit as the chain extender. Mesophase was found for all synthesized LC polyurethanes except of polymers H2‐A‐12 and H2‐A‐7. The structures and the thermal properties of all synthesized TLCPUEs were studied by using FTIR spectroscopy, wide‐angle x‐ray diffraction (WAXD) and DSC measurements, a polarizing microscope equipped with a heating stage, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). Mechanical properties were also examined by using a tensilemeter. © 1995 John Wiley & Sons, Inc.
Demonstration of methylene‐ether bridge formation in melamine‐formaldehyde resins
Authors: Scheepers M. L. , Adriaensens P. J. , Gelan J. M. , Carleer R. A. , Vanderzande D. J. , De Vries N. K. , Brandts P. M. 
Published: April 2003

Abstract1H and 13C NMR have been used for the quantitative determination of methylene‐ether bridges in melamine‐formaldehyde (MF) resins. The amount of methylene‐ether bridges was determined by 13C NMR from the number of monomethylolated amino groups consumed in the condensation reactions and is in agreement with that calculated from the condensation water contents. This latter method, which involves a combination of 1H and 13C NMR, is based on the amount of condensation water released during the formation of both methylene and methylene‐ether bridges. © 1995 John Wiley & Sons, Inc.
Thermosets obtained by chemical modification of epichlorohydrin‐ethylene oxide copolymer and their crosslinking through double bonds
Authors: Reina J. A. , Serra A. , Mantecón A. , Cádiz V. 
Published: April 2003

AbstractThe epichlorohydrin‐ethyleneoxide copolymer is modified with 10‐undecenoate and 4‐pentenoate moieties in order to obtain thermosets by cross‐linking through their double bonds. These polymers are then characterized using NMR, IR, chlorine elemental analyses, X‐ray powder diffraction, DSC, TGA, and viscosimetric measurements. Because the thermal crosslinking reaction overlaps in all cases with degradation processes, a free radical source (dicumyl peroxide) is necessary. The Arrhenius kinetic parameters are determined by DSC, using Ozawa and Kissinger expressions. Finally, the quality of cured materials is tested by TGA. © 1995 John Wiley & Sons, Inc.
Ferrocene as an effective initiator for copolymerization of styrene with maleic anhydride
Authors: Kuramoto Noriyuki , Ogino Hiroko , Kido Junji , Nagai Katsutoshi 
Published: April 2003

AbstractFerrocene (Fc) was found to be an effective initiator for copolymerization of styrene (ST) with maleic anhydride (MAH). Copolymerization could be initiated by charge transfer complex formed between MAH as an electron acceptor and Fc as an electron donor. A good relationship between the formation of charge transfer complex and initiation activity was observed in the copolymerization of ST with MAH in various solvents. Overall energy of activation determined from an Arrhenius plot in dioxane was found to be 21.8 kJ/mol. © 1995 John Wiley & Sons, Inc.
Olefin terpolymerizations. I. 1,4‐hexadiene
Authors: Yu Zhengtian , Marques Maria , Rausch Marvin D. , Chien James C. W. 
Published: April 2003

AbstractEthylene (E), propylene (P), and 1,4‐hexadiene (HD) were terpolymerized with rac‐1,2‐ethylenebis (1‐η5‐indenyl) zirconium(IV) dichloride and methylaluminoxane (Et[Ind]2ZrCl2/MAO), and compared with the copolymerizations of E/P, E/HD, P/HD, and terpolymerization using ethylidene norbornene (ENB) as the termonomer. HD lowers the polymerization activity, the effect is more pronounced for P/HD and E/P/HD using large amount of P, than for E/HD and E/P/HD using feed low in P. The polymer molecular weight is most strongly affected by the temperature of polymerization (Tp), whereas the E/P ratio in the feed has virtually no effect. The reactivity ratios rE and rP are 3.0 and 0.3, respectively, at 20°C but rP becomes larger than rE at TP = 70°C. 1H‐NMR spectra showed occurrence of cycloaddition in the homopolymerization of HD; on the other hand, HD is incorporated in the terpolymer only by linear 1,2‐addition. © 1995 John Wiley & Sons, Inc.
ansa‐Zirconocenium catalysis of syndiospecific polymerization of propylene: Theory and experiment
Authors: Yu Zhengtian , Chien James C. W. 
Published: April 2003

AbstractThe syndiospecific propylene polymerizations catalyzed by isopropylidene(cyclopentadienyl)(fluorenyl)‐ and (2,2‐dimethylpropylidene)(cyclopentadienyl)(fluorenyl)‐zirconocenium (1+ and 2+) have been investigated theoretically and compared with experimental observations. With the ab initio calculated structures for the transition state (TS) of 1+(M)P and 2+(M)P (M = propylene, P = 2‐methylpentyl), their steric energies (E°) have been computed using MM2 force‐field. The difference between steric energies E°(m) and E°(r) for the meso and racemic enchainment of propylene, respectively, is defined as the stereocontrol energy [δE°(m − r)] for syndiotactic propagation. The δE°(m − r) for the TS of 1+ (M)P is about 2.1 kcal/mol, the value is 1 kcal/mol greater for 2+(M)P. The observed steric pentad distributions of the syndiotactic poly(propylene) obtained by these catalysts are consistent with smaller effective stereocontrol energy, which is about two‐third as large as δE°(m − r) values calculated for the MM2 optimized structure. Syndiotactic enchainment is favored over isotactic enchainment for all combinations of site configurations in the catalyst. α‐Agostic interaction seems to enhance syndioselectivity, whereas γ‐agostic interaction changes the stereoselectivity to meso enchainment. The mirror plane symmetry of the syndiotactic propagating species renders the stereoselectivity of the polymerization insensitive to reaction conditions. These catalysts are also highly regiospecific. © 1995 John Wiley & Sons, Inc.
Modified horner–emmons reaction of polymeric phosphonates: Versatile synthesis of pendant stilbene‐containing polymers
Authors: Belfield Kevin D. , Wang Juexian 
Published: April 2003

AbstractPoly[styrene‐co‐(diethyl vinylbenzylphosphonate)] and poly[methylmethacrylate‐co‐(diethyl vinylbenzylphosphonate)] were prepared and used in modified Horner‐Emmons reactions to synthesize polymers with covalently attached stilbene groups. This versatile new method allowed for the preparation of polymers with either electron‐donor (OCH3, CH3) or electron acceptor (Br, NO2) substituents on the stilbene aromatic ring. The resulting polymers were characterized by 1H NMR, FT‐IR, UV‐visible, DSC, and size exclusion chromatography. Efficient transformation of polymeric phosphonates to the polymeric stilbene derivatives was realized. Size exclusion chromatographic analyses demonstrated that the reaction conditions have no deleterious effect on the molecular weight distribution of the various polymers that were prepared. Photochromic behavior was demonstrated for one of the derivatives. © 1995 John Wiley & Sons, Inc.
An amphiphilic graft copolymer as a surface‐modifying additive for poly(methyl methacrylate)
Authors: Zhu Liming , Gunnarsson Omar , Wesslén Bengt 
Published: April 2003

AbstractAn amphiphilic graft copolymer was prepared by transesterification of poly(2‐ethylhexyl acrylate‐co‐methyl methacrylate) with poly(ethylene glycol) monomethyl ether (MPEG2000). The grafting reaction was performed in melt at 155°C. The purified graft copolymer was blended into poly(methyl methacrylate) in concentrations of 1.5‐30 wt %, either by mixing in chloroform solution or by melt mixing by means of a twin‐screw extruder or a Brabender blender. Films of the blends were prepared by solution casting onto glass plates or by hot pressing between polished Al plates. At concentrations up to 20% of the graft copolymer homogeneous blends were obtained. At higher concentrations the blends were heterogeneous, and side‐chain crystallinity was detectable by DSC analysis. The surface properties of the films were studied by measurements of water contact angles. The surface accumulation of the graft copolymer was demonstrated as a large increase in the wetting angle hysteresis, and found to depend on the procedure for film preparation as well as the casting substrate. © 1995 John Wiley & Sons, Inc.
Poly‐3‐Hydroxyalkanoates containing unsaturated repeating units produced by pseudomonas oleovorans
Authors: Kim Y. B. , Lenz R. W. , Fuller R. C. 
Published: April 2003

AbstractPoly‐3‐hydroxyalkanoates (PHAs) containing repeating units with terminal alkene substituents at the 3‐position were produced by Pseudomonas oleovorans grown with either 7‐octeneoic acid [OA()] alone, or 10‐undeceneoic acid [UND()] alone, or mixtures of UND() and either nonanoic acid (NA) or octanoic acid (OA). For the latter, the biomass and PHA yields decreased as the fraction of UND() increased in the mixed carbon substrates. Essentially all of the repeating units in the PHA obtained from cells grown with UND() alone contained terminal alkene groups, including 3‐hydroxy‐10‐undeceneoate, 3‐hydroxy‐8‐noneneoate, and 3‐hydroxy‐6‐hepteneoate units, but less than half of the units in the PHA from OA() had alkene substituents. The PHAs obtained from cells grown with various mixtures of UND() and either OA or NA were random copolymers, and the fraction of units with alkene substituents in these polymers increased in proportion to the fraction of UND() in the mixed carbon substrates. © 1995 John Wiley & Sons, Inc.