bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethylene‐vinyl acetate semi‐batch emulsion copolymerization: Use of factorial experiments for process optimization
Authors: Scott P. J. , Penlidis A. , Rempel G. L. , Lawrence A. D. 
Published: April 2003

AbstractThe application of factorial experiments to optimize the ethylene‐vinyl acetate emulsion polymerization process is described herein. A prior extensive experimental phase identified those variables that are most important for ethylene‐vinyl acetate emulsion copolymer production. The effects of temperature, pressure, added co‐solvent, vinyl acetate feed rate and emulsifier type, and concentration on the rate of polymerization, cumulative copolymer composition, molecular weight averages, and particle size and number are described in this article. The primary objectives of this research were to increase the amount of ethylene that could be incorporated into the copolymer at reduced temperatures and pressures (our target was a copolymer with an ethylene content of 30% by weight at 500 psig and 20°C versus the commonly employed industrial conditions in excess of 1000 psig), to achieve an improved process understanding, and to accumulate reliable data for modelling purposes. A copolymer containing 34% by weight of ethylene has been achieved at a pressure of 500 psig and a temperature of 20°C. The confusion present in the literature surrounding emulsifier effects has also been clarified. A discussion of hydrolysis, experimental reproducibility, and glass transition temperatures is also included. The sequential nature of the experimental process is illustrated throughout these optimizing experiments. © 1994 John Wiley & Sons, Inc.
Ring‐Opening polymerization of ε‐caprolactone by rare earth coordination catalysts. I. Characteristics, kinetics, and mechanism of ε‐caprolactone polymerization with nd(acac)3.3H2O‐ALET3 system
Authors: Shen Zhiquan , Chen Xianhai , Shen Youqing , Zhang Yifeng 
Published: April 2003

AbstractRing‐opening polymerization of ε‐caprolactone has been carried out by using rare earth coordination catalysts for the first time. The rare earth compounds, RE(acac)3.3H2O, Nd(P204)3, Nd(P507)3, Nd(naph)3, Nd(BA)3.2H2O, etc. (where RE = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Lu, Y; acac = acetylacetone; BA = benzoylacetone), combined with trialkyl aluminum, greatly increased the degree of conversion and the molecular weight of poly(ε‐caprolactone) (PCL). The influence of reaction conditions on the polymerization of ε‐caprolactone catalyzed by the Nd (acac)3.3H2O‐AlEt3 system has been examined in detail. The kinetics indicates that the polymerization rate has the first‐order in monomer and a half‐order in catalyst. The overall activation energy of the ring‐opening polymerization amounts to 59.4 kJ/mol. By IR and UV‐Vis spectra, 1H‐ and 13C‐NMR data, it is assumed that the ring‐opening polymerization of ε‐caprolactone catalyzed by the Nd(acac)3.3H2O‐AlEt3 system proceeds via complexation of monomer to catalyst, acyl‐oxygen cleavage insertion propagation mechanism. © 1994 John Wiley & Sons, Inc.
The synthesis and cationic polymerization of multifunctional silicon‐containing epoxy monomers and oligomers
Authors: Crivello J. V. , Bi Daoshen 
Published: April 2003

AbstractSeveral series of multifunctional silicon‐containing epoxide monomers and oligomers have been prepared using rhodium catalyzed hydrosilation reactions. Dialkyl and diarylsilanes can be condensed with vinyl epoxides to give high yields of the desired diepoxides while the hydrosilation of alkyl and aryl silanes yields a mixture of di and tri epoxy substituted products. The condensation of αω,SiH difunctional compounds with vinyl epoxides can be carried out regioselectively to give α‐hydrogen‐ω‐epoxy intermediates, which can be further reacted with di and tri olefins bearing terminal double bonds to give a series of well characterized epoxy functional oligomers. An investigation of the photoinitiated cationic polymerization of the monomers and oligomers, which were prepared during the course of these studies, was carried out. © 1994 John Wiley & Sons, Inc.
Synthesis of ion‐free latex particles composed of polybutadiene and poly (vinyl pyrrolidone) as polymer electrolyte materials
Authors: Rutt J. Steven , Ichino Toshihiro , Matsumoto Morihiko , Nishi Shiro 
Published: April 2003

AbstractThe synthesis of polybutadiene (PB) by emulsion polymerization with use of poly (vinyl pyrrolidone) (PVP) stabilizer was investigated. The goal was to prepare flexible latex films that clearly retain particle morphology in the solid state after heat treatment and contain no ionic, hydroxyl, or (primary, secondary) amino groups. The latex particle core composed of PB was nonpolar and rubbery, while the particle shell composed of PVP was polar and glassy. Average particle diameter was measured by the dynamic light scattering technique, and particles were imaged by scanning and transmission electron microscopic analyses. Dialysis of the latices resulted in successful exchange of the dispersion medium without precipitation. © 1994 John Wiley & Sons, Inc.
Reduced titanium dioxide as support for Ziegler–Natta catalysts
Authors: Jericó Soraya , Schuchardt Ulf , Kaminsky Walter , Joekes Inés 
Published: April 2003

AbstractTitanium tetrachloride heterogenized on reduced TiO2has been studied as a catalyst for ethylene polymerization. The catalyst has good storage stability and exhibits good activity for ethylene polymerization. The polymer chains grow linearly during ca. 1 h, giving an average molecular weight of up to 2.5 × 106which indicates that practically no β‐elimination occurs. The activity of the catalyst at 50°C, based on Ti(III), is 7.6 × 106PE/mol Ti h bar and based on the quantity of polyethylene formed it is 1.25 × 106g PE/mol Ti h bar. The molecular weight of the polymer can be controlled with the addition of hydrogen, under 0.5 bar hydrogen, polyethylene with a molecular weight of 411,000 and a relatively low polydispersity index of 2.2 is obtained. The catalyst shows good thermal stability; the Arrhenius activation energy is 31.8 kJ/mol for the polymerization. The catalyst is also active for propylene polymerization, giving 3 × 106g PP/mol Ti h bar with the high isotacticity of 93%. © 1994 John Wiley & Sons, Inc.
Ethylene‐hindered amine copolymer: A self‐stabilized polyolefine
Authors: Bertolini Guglielmo , Lanzini Luigi , Marchese Luca , Roggero Arnaldo , Lezzi Alessandro , Costanzi Silvestro 
Published: April 2003

AbstractMonomers having a norbornene as polymerizable group and a 2,2,6,6‐tetramethyl piperidine as stabilizing moiety were prepared. This monomer was successfully copolymerized with ethylene using VAc3/AlEt2Cl as the catalytic system. Copolymers exhibited better stability under accelerated aging than polyethylene stabilized by classical blending with commercial hindered amines. Any attempt made to obtain copolymers using a high activity TiCl4/MgCl2 catalyst was unsuccessful. © 1994 John Wiley & Sons, Inc.
Prediction of polymer composition in batch emulsion copolymerization
Authors: Noël Lilian F. J. , Van Zon Jan M. A. M. , Maxwell Ian A. , German Anton L. 
Published: April 2003

AbstractMonomer partitioning in emulsion copolymerization plays a key role in determining composition drift and polymerization rates. The combination of recently developed thermodynamically based monomer partitioning relationships with mass balance equations, makes predictions of monomer partitioning in emulsion copolymerizations possible in terms of monomer mole fractions and monomer concentrations in the particle and aqueous phases. Using this approach, the effects of monomer to water ratios and polymer volumes on the monomer mole fraction within the polymer particle phase in a nonpolymerizing system at thermodynamic equilibrium can be determined. Comparison of these monomer partitioning predictions with experiments for the monomer system methyl acrylate—vinyl acetate shows good agreement. Furthermore, composition drift occurring in a polymerizing system as a function of conversion can be predicted if the assumption is made that equilibrium is maintained during reaction. Comparison of predictions with experimental results for emulsion copolymerizations of the monomer systems methyl acrylate—vinyl acetate and methyl acrylate—indene shows good agreement. © 1994 John Wiley & Sons, Inc.
Reactivity characteristics of squid β‐chitin as compared with those of shrimp chitin: High potentials of squid chitin as a starting material for facile chemical modifications
Authors: Kurita Keisuke , Ishii Shigeru , Tomita Koji , Nishimura Shin‐Ichiro , Shimoda Kayo 
Published: April 2003

AbstractChemical reactivity of β‐chitin isolated from squid pens has been examined in various reactions to elucidate the possibility of facile modifications in simple manners leading to the preparation of derivatives with well‐defined structures. β‐Chitin swelled in common solvents such as methanol and pyridine unlike the ordinary α‐chitin and exhibited much higher reactivity than β‐chitin. Free amino groups present in β‐chitin were easily and selectively acetylated with acetic anhydride in methanol to give chitin with a uniform structure, poly(N‐acetyl‐D‐glucosamine). When acetylation reaction was carried out in pyridine, O‐acetylation proceeded smoothly besides N‐acetylation. In the presence of 4‐dimethylaminopyridine as the catalyst, even full acetylation was achieved under mild conditions. Tosylation was also quite efficient in pyridine without side reactions such as N‐deacetylation which is unavoidable in the tosylation of α‐chitin. β‐Chitin also enabled direct tritylation in pyridine in the presence of 4‐dimethylaminopyridine. All these reactions were quite sluggish with β‐chitin, and no reactions or only very low extents of substitution were observed, indicating the high potential of β‐chitin as a versatile starting material for facile modification reactions. © 1994 John Wiley & Sons, Inc.
Preparation of polyalkylviologen–polyanion complexes and their applications to the debromination of diphenyl bromomethane under heterophase condition
Authors: Liu Futian , Yu Xianda , Li Shuben 
Published: April 2003

AbstractSeveral polyelectrolyte complexes were prepared by the reaction of polyalkylviologens [polyethylviologen (PEV2+), polypropylviologen (PPrV2+), and polybutylviologen (PBV2+)] with polyanions [sodium alginic (ALG), sodium polyacrylate (PAA), or sodium polystyrenesulfonate (PSS)]. These complexes were used as electron‐transfer catalysts (ETC) on the debromination of diphenyl bromomethane (Ph2CHBr) under heterophase condition [reductant: Na2S2O4, in H2O (liquid)‐polyelectrolyte complex(S)—Ph2CHBr in CH2Cl2]. The work showed that these complexes could induce the debromination of Ph2CHBr to afford tetraphenyl ethane, and different polyanions in the complexes also affected the mediating abilities. © 1994 John Wiley & Sons, Inc.
Synthesis and characterization of new fluorescent poly(arylene ether)s
Authors: Matsuo Shigeru , Yakoh Naoto , Chino Shinji , Mitani Masahiro , Tagami Sanae 
Published: April 2003

AbstractThe poly(arylene ether)s were prepared by the nucleophillic aromatic substitution polymerization of phenolphthalin and its derivatives with activated aromatic difluorides. The polymers had glass transition temperatures ranging from 210 to 240°C. Though the monomers have no fluorescence, the resulting polymers fluoresced a light green color in solid and solution states. The maximum excitation and emission wavelengths are 420 nm and 470 nm, respectively. In the polymer solutions, the fluorescence intensity decreased gradually, but the intensity was recovered by heating the polymer at 220°C for a few minutes. The fluorescent polymer had a stable radical. A model compound having the same repeating unit of the polymer was also prepared. The fluorescence properties of this model were almost the same as those of the polymers. © 1994 John Wiley & Sons, Inc.
Synthesis and thermal behavior of side‐chain liquid crystalline polymethacrylates containing tolane‐based mesogenic side groups
Authors: Hsieh Chang‐Jyh , Wu Shih‐Hsiung , Hsiue Ging‐Ho , Hsu Chain‐Shu 
Published: April 2003

AbstractThe synthesis and characterization of nine polymethacrylates containing 4‐alkoxy‐4′‐trifluoromethyltolane, 4‐alkoxy‐4′‐cyanotolane, and 4‐alkoxy‐4′‐nitrotolane side groups were described in this study. The phase behavior of the prepared monomers and polymers was characterized by differential scanning calorimetry, optical polarizing microscopy, and x‐ray diffraction. All of the obtained monomers exhibit no mesophase, while most of the synthesized polymers reveal enantiotropic mesomorphism. The polymethacrylate containing 4‐propanyloxy‐4′‐nitrotolane side groups was the only one which shows no mesomorphic behavior. Both the spacer length and the nature of terminal groups have profound influence on the phase transition temperatures and thermal stability of the mesophase. The polymers with longer spacers tend to form a more ordered mesophase with a wider temperature range. Among three polymers with the same spacer length, the polymer with a trifluoromethyl terminal end group is inclined to form a more ordered mesophase than the other two polymers. No side chain crystallization occurred for all obtained polymers. © 1994 John Wiley & Sons, Inc.
1H‐NMR and UV studies of Rh complexes as a stereoregular polymerization catalysts for phenylacetylenes: Effects of ligands and solvents on its catalyst activity
Authors: Tabata Masayoshi , Yang Wu , Yokota Kazuaki 
Published: April 2003

AbstractPhenylacetylene and its homologues bearing methoxy or chloro groups in the para position of the phenyl ring were stereoregularly polymerized by Rh complex catalysts, e.g., [Rh (norbornadiene) Cl]2, in the presence of various solvents. The 1H‐NMR and UV study of the Rh complex showed that the activity of the Rh catalysts greatly depends upon not only the ligand in the Rh catalyst but also on the solvent used, e.g., polyphenylacetylene with a highly cis‐transoidal content was quantitatively obtained when norbornadiene was coordinated as the ligand, and triethylamine (TEA) was used as solvent, whereas tetrahydrofuran (THF) and benzene reduced the cis content. It was also found that the Rh catalyst as a dimer complex dissociates into the monomeric species not only when TEA was used but also when alcohol, benzene, and THF were used. The resulting monomeric species was considered as the important propagation species in this polymerization. The sharp line width observed in the 1H‐NMR spectrum of polyphenylacetylene and its homologues which were prepared in ethanol or TEA was interpreted by the narrow chemical shift distribution arising from the high cis content. © 1994 John Wiley & Sons, Inc.
Optically active polymers containing side‐chain photochromic moieties: Synthesis and chiroptical properties of copolymers of trans‐4‐(phenylazo)‐1‐naphthyl acrylate and trans‐4‐(1‐naphthylazo)‐phenyl acrylate with ()‐menthyl acrylate
Authors: Angiolini Luigi , Caretti Daniele , Carlini Carlo 
Published: April 2003

AbstractThe synthesis of photochromic optically active copolymers from trans‐4‐(phenylazo)‐1‐naphthyl acrylate (PANA), or trans‐4‐(1‐naphthylazo)‐phenyl acrylate (NAPA), and (−)‐menthyl acrylate (MtA) is described. The copolymers prepared, having different contents of trans‐phenylazonaphthalene moieties, have been characterized by IR, 1H‐NMR, UV, and GPC techniques. The chiroptical properties have been investigated by circular dichroism (CD) and the induced optical activity on the side‐chain trans‐phenylazonaphthalene chromophores discussed in terms of different conformational situations of the macromolecules in both the copolymer series. © 1994 John Wiley & Sons, Inc.
A reexamination of the degradation of polyvinylchloride by thermal analysis
Authors: Chatterjee Nandini , Basu Sudhapada , Palit S. K. , Maiti Mrinal M. 
Published: April 2003

AbstractDegradation of polyvinylchloride has been reexamined in the light of its DT‐DSC‐TG analytical behavior up to a temperature of 1000°C in an inert atmosphere. Four distinct stages of degradation have been identified. The first stage is almost eventless with no change in weight for untreated PVC samples. The second stage is almost exclusively dehydrochlorination. The third stage appears to be a structural reorganization involving such processes as cis‐trans isomerization, aromatization, and crosslinking. The fourth stage appears to be a structural degradation and is associated with the evolution of hydrocarbons. The role of liberated hydrogen chloride has been better appreciated in catalyzing the above secondary reactions on the polyene residue obtained on partial or total dehydrochlorination. The effect of the particle dimension and chemical and physical pretreatments of the samples, such as low temperature dehydrochlorination by an alkali and vacuum heat treatment, respectively, on the degradation pattern has been studied. © 1994 John Wiley & Sons, Inc.
Syntheses of homopolymer and water‐soluble polymers containing tetraphenylporphinatomanganese(III) complex, and ligand substitution reaction for anionic ligand
Authors: Sumi Katsuhiro , Kimura Mutsumi , Nakamura Isei 
Published: April 2003

AbstractA vinyl monomer containing the pendant tetraphenylporphyrin (TPP) group, 4‐vinyltetraphenylporphyrin (VTPP), was synthesized. A homopolymer (PVTPP) which is insoluble in water, and three water‐soluble polymers were obtained by radical polymerization. The water‐soluble polymers are two anionic polymers (PVPTSPP and PVTPP‐StSO3) and a cationic polymer (PVTPP‐VPyM). PVPTSPP has sulfonic acid groups in a TPP group and very high charge density. PVTPP‐StSO3 was obtained by copolymerization of VTPP and sodium 4‐styrenesulfonate. PVTPP‐VPyM was obtained by quarternarization of a copolymer of VTPP and 4‐vinylpyridine. Polymeric manganese(III) complexes (PMn‐VTPP, PMnVPTSPP, PMnVTPP‐StSO3, and PMnVTPP‐VPyM) were prepared from the polymers and manganese acetate. The acetate ligand in PMnVTPP can be easily substituted by another ligand such as Cl−, AcO−, OH−, and SCN−. The substitution reaction occurs in the interface between water and chloroform. The sulfonated homopolymer, PMnVPTSPP, cannot incorporate with anionic ligands because of the strong electrostatic repulsion. In the anionic copolymer, PMnVTPP‐StSO3, the ligand substitution reaction with SCN ligand needs activation energy of 53 kJ/mol. In the cationic polymer complex, PMnVTPP‐VPyM, the OH ligand can be easily substituted with the SCN ligand and the equilibrium constant of the reaction was estimated at 1.38 × 10−3. © 1994 John Wiley & Sons, Inc.
Studies on the formation of PEN. I. Kinetic aspects of catalyzed reaction in transesterification of dimethylnaphthalate with ethylene glycol
Authors: Wang Chun‐Shan , Sun Yih‐Min 
Published: April 2003

AbstractThe transesterification of dimethyl naphthalate (DMN) with ethylene glycol (EG) was kinetically investigated in the presence of various catalysts at 185°C. The transesterification was assumed to obey first‐order kinetics with respect to DMN and EG, and a rate equation was derived. The rate constant of transesterification which was calculated from the quantity of methanol which distilled from the reaction vessel was used to evaluate the activity of each metal compound. The first‐order dependence on the catalyst concentration is valid below a critical concentration which was found to be dependent on the catalyst type. The order of decreasing catalytic activity of various metal ions was found to be: Pb ≥ Zn > Co > Mg > Ni ≥ Sb, but in the case of highly basic metal salts, the rate constants were found to be extremely large at the initial stage of the reaction, and then rapidly decreased with the progress of the reaction. Effects of reaction temperature were also discussed. The activation energies for zinc acetate and lead acetate were 97.84 and 108.8 kJ/mol, respectively, which were calculated from the Arrhenius equation. © 1994 John Wiley & Sons, Inc.
Macrothiuram disulfide for the free radical synthesis of PDMS‐vinyl triblock copolymers. II. Studies of chain transfer
Authors: Clouet G. , Kayser D. 
Published: April 2003

AbstractChain transfer constants (Ctr) for thiuram disulfide (TD) groups, included in the backbone of polydimethylsiloxane (PDMS) of different chain lengths, in methyl methacrylate (MMA) and styrene (St) were determined from measurements of the degree of polymerization. Two methods were used. The first consisted of using the initiation and transfer properties of the thiuram disulfides groups, and the second, of using a more efficient free radical initiator than TD groups, in which case the former behaves only as a transfer agent. In both the methods, the Ctr of TD was evaluated in bulk polymerization of MMA at 60, 70, 80, and 90°C. Using the first method, the Ctr of TD was measured also in solution polymerization of MMA in toluene at 100°C and, with the second one, in bulk polymerization of styrene at 60, 80, and 90°C. PDMS‐based macrothiuram disulfide (macroiniferter) behaves as an “azeotropic” transfer agent for MMA and styrene at 125°C and 110°C, respectively. © 1994 John Wiley & Sons, Inc.
Two‐Dimensional polymerization of supramolecular assemblies: Synthesis and bilayer polymerization of lipids containing α‐methylene‐substituted acyl chains
Authors: Lee Youn‐Sik , O'Brien David F. 
Published: April 2003

AbstractPolymerization of lipid assemblies may be usefully employed to alter the properties of the assemblies. The possible locations of the reactive group in the lipids include (1) the chain terminus, (2) the head group, and (3) near the lipid backbone. The third strategy yields polymerized assemblies which retain their head group functionality and lipid chain motion. We have designed and synthesized new members of this later category by the use of 2‐methylene‐substituted acyl chains. The main transition temperature (Tm) from gel to liquid crystalline phase of hydrated bilayers of 1‐palmitoyl‐2‐(2‐methylene)palmitoyl‐sn‐glycero‐3‐phosphocholine (1) and the disubstituted 1,2‐bis(2‐methylenepalmitoyl)‐sn‐glycero‐3‐phosphocholine (2) were 33.6 and 25.3°C, respectively. The Tm of the mono‐substituted 1‐oleoyl‐2‐(2‐methylene)palmitoyl‐sn‐glycero‐3‐phosphocholine (3) bilayers was detected in a range from −15 to −10°C by x‐ray diffraction. Hydrated bilayers of each individual lipid were successfully polymerized with a water‐soluble initiator, azobis(2‐amidinopropane) dihydrochloride (AAPD). These results indicate the lipid 2‐methylene groups are accessible to the water interface. Thermal polymerization of the mono‐substituted lipids in aqueous suspensions with AAPD, yielded oligomers. However the bis‐2‐methylene PC (2) was successfully polymerized to yield stabilized crosslinked bilayers. © 1994 John Wiley & Sons, Inc.
Self‐Crosslinkable poly(arylene ether)s containing pendent phenylenetriazene groups
Authors: Lau Aldrich N. K. , Vo Lanchi P. , Fone Matilda M. , Duff David W. , Merlino Gloria 
Published: April 2003

AbstractSelf‐crosslinkable poly(arylene ether)s 6, and 8, containing pendent triazene groups were prepared by nucleophilic substitution reaction of poly(arylene ether)s 5, and 7, respectively, with 1‐[4‐(4‐hydroxyphenoxy)phenylene]triazenes, 4, in the presence of potassium carbonate in N,N‐dimethylacetamide. A series of triazenes 4 containing various substituents have been synthesized. Self‐crosslinkable polymer 6e containing phenyl‐substituted triazene pendants can be crosslinked at 215°C, which is about 40°C lower than the glass transition temperature of the virgin base polymer 5. The degree of crosslinking can be tailored by varying the concentration of the pendent phenylenetriazene groups in the polymer. After curing, the flexible polymer films (ca. 10 μm thick) exhibit high gel contents, increased glass transition temperatures, improved resistance to organic solvents, and little change in dielectric constant and thermal stability. These self‐crosslinkable poly(arylene ether)s are potential candidates for electronic applications. © 1994 John Wiley & Sons, Inc.