bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copolymers of vinyl fluoride
Authors: Korin Amos , Levy Moshe , Vofsi David 
Published: April 2003

AbstractVinyl fluoride was polymerized by photochemical initiation in a continuous‐flow cylindrical reactor at room temperature and at pressures of up to 30 atm. Copolymers with vinyl acetate were prepared in order to improve the solubility and processability of poly(vinyl fluoride) (PVF). The copolymers were hydrolyzed to the corresponding vinyl alcohol copolymers and yielded hydrophilic films that are strong and flexible only when swollen by water. It was found that on hydrolysis the Tg, Tm, and heat of fusion as well as degree of crystallinity increased. It was suggested that PVF and the copolymers with vinyl alcohol are isomorphous.
Mechanistic studies on ceric‐thiourea‐initiated polymerization of methyl methacrylate in acid‐aqueous media from end group analysis
Authors: Pramanick D. , Chatterjee A. K. 
Published: April 2003

AbstractThe mechanism of the redox polymerization of methyl methacrylate in acid‐aqueous medium was studied for ceric‐thiourea initiator system by analysis of polymer end groups using the dye partition method. Polymerization at room temperature and at pH 2.30 with this initiator system incorporates mostly amino end groups in the polymers to the extent of 1.18‐1.31 and a small amount of hydroxyl end group not exceeding 0.08 per polymer molecule. Under the same pH condition, a higher polymerization temperature increases the amine end group content to 2.17‐2.30 and hydroxyl end group content to 0.14‐0.18 per polymer molecule. A lower polymerization temperature (5°C), or a lower pH (ca. 1) of the reaction medium, produces polymers with exclusively amine end groups, hydroxyl end groups being totally absent. At pHs greater than 3, amine end group incorporation decreases significantly, with simultaneous increase in hydroxyl incorporation. On the basis of end group results the initiating radical has been identified and the mechanism of initiation has been suggested. The possible mode of termination has also been discussed.
Kinetic evidence of a “matrix effect” in the bulk polymerization of acrylonitrile
Authors: Burillo G. , Chapiro A. , Mankowski Z. 
Published: April 2003

AbstractThe kinetics of the γ‐ray‐initiated polymerization of acrylonitrile in bulk are reexamined in broad ranges of temperatures and radiation dose rates. The discussion of the results coupled with an analysis of earlier data indicate that the polymerization of acrylonitrile proceeds by different mechanisms depending on the reaction temperature. Above 60°C the precipitated growing chains recombine readily; therefore, the autoaccelerated conversion curves cannot be accounted for by an “occlusion effect.” It is suggested that autoacceleration is caused by a fast propagation taking place in oriented monomer aggregates which result from dipole‐dipole association of the monomer with the polymer chains formed in the early stages of the reaction (“matrix effect”). Below 10°C the precipitated growing chains are buried in the dead polymer and monomer diffusion toward the occluded chain ends is very limited (“occlusion effect”). Between 10 and 60°C the system gradually changes from one dominated by “occlusion” to one where the “matrix effect” determines the kinetic behavior. The conclusion based on kinetic data is in agreement with results obtained from studies of the postpolymerization in these various systems.
Functional monomers and polymers. LXI. Photochemical reactions on the synthetic polymers containing thymine bases
Authors: Kita Y. , Inaki Y. , Takemoto K. 
Published: April 2003

AbstractPhotodimerization of N‐2‐isobutyloxyethyl thymine (T‐M), bis[2‐(5‐methyl‐1‐primidinyl)‐ethyl] glutarate (T‐T), poly(N‐2‐methacryloyloxyethyl thymine) (polyMAOT), and poly(N‐2‐acryloyloxyethyl thymine) (poly AOT) was studied in dimethylformamide solution. The rate of intramolecular photodimerization of polyMAOT and polyAOT was 5.7 and 7.2 times faster, respectively, than that of T‐T. In T‐M, however, intermolecular photodimerization did not occur under the reaction condition used. Quenching studies with isoprene suggest that the photodimerization of T‐T occurs predominantly in an excited triplet state, whereas that of polyMAOT and polyAOT occur in singlet and triplet states. It was concluded that the photodimers of T‐T, polyMAOT, and polyAOT are two syn‐fused cyclobutane‐type dimers (cis‐syn and trans‐syn). Quantum efficiencies of thymine base disappearance were determined by ultraviolet (UV) analysis to be 0.0012 for T‐T, 0.0084 for polyMAOT, and 0.010 for polyAOT.
Reaction of cellulose phosphonate with N‐vinyl‐2‐pyrrolidone and flame‐retardant properties of the product
Authors: Inagaki Norihiro , Katsuura Kakuji 
Published: April 2003

AbstractThe reaction of cellulose phosphonate and N‐vinyl‐2‐pyrrolidone in ethanol in the presence of sodium ethoxide was investigated and thermal stabilities and flame‐retardant properties for cellulose phosphonate modified with N‐vinyl‐2‐pyrrolidone were discussed. The results in this study point out the following important aspects of flame retardation of cellulose fabrics: (1) The reaction of cellulose phosphonate and N‐vinyl‐2‐pyrrolidone in the presence of sodium ethoxide results in graft polymerization of N‐vinyl‐2‐pyrrolidone at PH sites in cellulose phosphonate; an average chain length of the graft polymer is about five units of vinylpyrrolidone. (2) The graft polymerization of N‐vinyl‐2‐pyrrolidone can improve both stabilities, especially the flame‐retardant properties of cellulose fabrics. (3) Amides, whether noncyclic or cyclic, are suitable for nitrogen compounds that can effectively operate as synergists.
Stepwise polymerization of 1,1‐diphenylethylene derivatives by acid catalysts
Authors: Nishimura J. , Tanaka N. , Hayashi N. , Yamashita S. 
Published: April 2003

AbstractThe polymers containing units of 1,1,3,3‐tetraphenylbut‐1‐ene [unit (I)] and/or units of 3‐methyl‐1,1,3‐triphenylindan [unit (II)] in the main chain were prepared by acid‐catalyzed dimerization of 1,1‐diphenylethylene applied to its bifunctional derivatives, for example bis[p‐(1‐phenylvinyl)phenyl]methane. The structure of yielded polymers depended on catalyst, solvent, temperature, and the molar ratio between the catalyst and the monomer. The molecular weight of polymer having unit (I) was determined by the equilibrium existing between 1,1‐diphenylethylene moiety and unit (I). It was shown clearly by gel permeation chromatography that the molecular weight of polymer having unit (II) grew further after the equilibrium mentioned above had been accomplished. The mechanism of the polymerization is discussed.
Aminolysis of crosslinked polysiloxanes: Tautomeric catalysis by 2‐pyridone
Authors: Pappas S. Peter , Just Ronald L. 
Published: April 2003

AbstractResults are presented which extend earlier findings on the transformation of insoluble crosslinked polysiloxanes into soluble linear polymers by selective aminolysis at crosslink sites. The present study provides evidence of a substantial steric effect and catalysis by 2‐pyridone. The results with 2‐pyridone are attributed to tautomeric catalysis which, to our knowledge, had not been observed before in substitution reactions at silicon. Evidence is also presented that unhindered, difunctional primary amines effect aminolysis with both amine groups to produce insoluble crosslinked polymer, presumably with silylamine functionality at crosslink sites.
Photochemical synthesis of new polymer structures. II. Photocycloaddition of olefins to polyvinylbenzophenone and poly(styrene‐co‐vinylbenzophenone)
Authors: Holden D. A. , Guillet J. E. 
Published: April 2003

AbstractThe photocycloaddition of simple olefins to poly(4‐vinylbenzophenone) (PVB) and poly(styreneco‐4‐vinylbenzophenone) (PS‐VB) was studied in benzene solution and in the solid polymer. In solution oxetane yields of 61–82% were obtained with di‐, tri‐, and tetrasubstituted olefins, which are visualized as capable of giving a radical on a 3° carbon atom in the biradical preceding ring closure to form the oxetane. Photocycloaddition of isobutene to PVB and PS‐VB occurs in solid polymer films to more than 90% conversion of the polymer ketone. Quantum yields of oxetane formation are 0.013 ± 0.003 on irradiation at 366 nm, independent of film thickness between 1.9 and 10.6 μm and of temperature between 23 and 65°C. The absence of a pronounced effect of the polymer glass transition on the efficiency of the cycloaddition in PVB suggests that large‐scale molecular motion is not required by this solid‐state photoreaction. Crosslinking by photochemical cycloaddition was demonstrated in mixed films of PVB and squalene, a polyfunctional olefin.
Polycarbonates from 1,1‐dichloro‐2,2‐bis(4‐hydroxyphenyl)ethylene and bisphenol A: A highly flame‐resistant family of engineering thermoplastics
Authors: Factor Arnold , Orlando Charles M. 
Published: April 2003

AbstractAlthough the preparation of polycarbonates based on bisphenol A and 2,2‐bis(4‐hydroxyphenyl)‐1,1‐dichloroethylene was disclosed in 1964 by Porejko et al., little has been reported on their physical and flammability properties. To define the properties of this system these materials were prepared and evaluated. The results indicate that the copolymers and blends of the homopolycarbonates of the two different bisphenols result in transparent thermoplastics that have almost the same attractive physical properties as the homopolycarbonate from bisphenol A. In addition, many of these formulations possess flame‐resistant properties that exceed those of other transparent thermoplastics; for example, highest OI and lowest smoke and lowest ratings in the ASTM E84 tunnel and E162 radiant panel tests. Preliminary bioassay results with rats of the products from 500°C air pyrolysis gave an ALC50 value greater than that of other common thermoplastics.
Comparative study of the photodegradation of polybenzoxazoles and related model compounds. Stabilization of polybenzoxazoles
Authors: Despax B. , Paillous N. , Lattes A. , Paillous A. 
Published: April 2003

AbstractPolybenzoxazoles (PBO) are thermally stable polymers whose possible use under space conditions as a transparent coating aboard spacecraft is restricted by their photodegradability. This photodegradability, which results in a loss of optical properties, is due to the structural features of benzoxazoles as well as to the presence of residual impurities from the synthesis (ketones, esters, amides). Suitable structural changes, which were intrinsic (increase in the conjugation) or extrinsic (addition of nickel salts able to complex the benzoxazole units), allowed the PBO photochemical stability to be increased and subsequently their optical transparency to be maintained. The fluorescence inhibition observed when nickel salts were added suggests that, in this case, stabilization results from a singlet‐singlet energy transfer. The effect of the various structural factors investigated on the stability of polybenzoxazoles was correlated with the photochemical behavior of the corresponding model compounds.
Extended‐chain polyamides: Polyoxamides and polyfumaramides
Authors: Pletcher T. C. , Morgan P. W. 
Published: April 2003

AbstractThe synthesis of polyamides from short‐chain aliphatic diacids, such as oxalic and fumaric acids, is difficult because of the thermal instability and volatility of the intermediates and side reactions with the polymerization media. A variety of synthetic routes to these polymers has been explored. Several aromatic polyoxamides with high molecular weight were obtained in high yield by an acid chloride vapor‐solvent‐water interfacial process. Polyoxamides of intermediate molecular weight also were obtained by preparation of oligomers from diamines and oxalic diesters and condensing these oligomers further in a thermal polymerization step. Aromatic polyfumaramides and terephthalamidefumaramides were prepared by modified solution procedures in amide solvents. Another route to polyfumaramides was the synthesis of N,N′‐bis(4‐aminophenyl) fumaramide and its use as a diamine with diacid chloride. The 1,4‐phenylene and benzidine polyfumaramides and oxamides have extended‐chain structures in solution in sulfuric, chlorosulfonic, and fluorosulfonic acids. Some of the polymers were soluble enough to yield liquid crystalline solutions. High‐tenacity high‐modulus fibers from poly(1,4‐phenylene fumaramide/terephthalamide)s are described.
Studies on polyyne polymers containing transition metals in the main chain. IV. Polymer synthesis by oxidative coupling of transition metal‐bis(acetylide) complexes
Authors: Takahashi S. , Murata E. , Sonogashira K. , Hagihara N. 
Published: April 2003

AbstractThe metal‐polyyne polymers consisting of transition metals and conjugated tetrayne systems
magnified image
where M represents Pt(PBu3)2 or Pd(PBu3)2 moiety were prepared by the oxidative coupling method and characterized by spectral analysis, associated with novel depolymerization giving binuclear transition metal complexes, and
Polycondensation of diethyl mucate with hexamethylenediamine in the presence of poly(vinyl pyridine)
Authors: Ogata Naoya , Sanui Kohei , Nakamura Hiroyuki , Kishi Hiroyuki 
Published: April 2003

AbstractThe polycondensation reaction of diethyl mucate (DEM) with hexamethylenediamine (HMD) was carried out in dimethyl sulfoxide (DMSO) at 60°C in the presence of poly(vinyl pyridine) (P‐VPy) as a matrix polymer, which was expected to interact with DEM or the resulting polyamide which had pendant hydroxyl groups due to a hydrogen bonding. It was found that the polycondensation of DEM with HMD in the presence of poly(4‐vinyl pyridine) (P‐4VPy) produced a polyamide with a higher molecular weight than those in the presence of poly(2‐vinyl pyridine) (P‐2VPy) or in the absence of P‐4VPy. The rate of the polycondensation, however, was rarely enhanced by polymer matrixes such as P‐4VPy and P‐2VPy. During polycondensation in the presence of P‐4VPy a gelation of the reaction mixture was observed when the solution was kept at 30°C for several days. This might be ascribed to the formation of the polymer complex between resulting polyamide and P‐4VPy during the polycondensation.
Polycondensation reaction of dimethyl tartrate with hexamethylenediamine in the presence of various matrices
Authors: Ogata Naoya , Sanui Kohei , Nakamura Hiroyuki , Kuwahara Masato 
Published: April 2003

AbstractThe polycondensation reaction of dimethyl tartrate (DMT) with hexamethylenediamine (HMD) was carried out in dimethyl sulfoxide (DMSO) at 60°C in the presence of various polymer matrices, which were expected to interact with DMT or the resulting polyamide which had pendant hydroxyl groups due to hydrogen bonding. It was found that the rate of polycondensation was enhanced by polymer matrices such as poly(vinyl pyrrolidone) (PVP), Pullulan (polysaccharide) (PF), and poly(vinyl alcohol) (PVA). The rate enhancement became more pronounced with increasing molecular weight of the polymer matrix. When polycondensation in the presence of PVA was carried out in DMSO, a polymer complex was produced. The formation of the polymer complex between the resulting polyamide and PVA during polycondensation was dependent on the concentration of monomers and also on PVA; a gelation of the solution was observed at a concentration of PVA.
Organosilane polymers. II. Poly(ethylmethyl‐co‐dimethylsilylene) and poly(methylpropyl‐co‐dimethylsilylene)
Authors: Wesson J. P. , Williams T. C. 
Published: April 2003

AbstractPolydimethylsilylene is a largely crystalline, high‐melting polymer that is soluble only above 200°C and does not thermoform below its decomposition temperature. Introduction of ethyl and propyl substituents into the linear silylene system by random copolymerization of dimethylsilylene with ethylmethyl‐ and methylpropylsilylenes leads to tractable polymers that are soluble in common solvents at normal ambient temperatures.
Photoinitiated cationic polymerization by dialkyl‐4‐hydroxyphenylsulfonium salts
Authors: Crivello J. V. , Lam J. H. W. 
Published: April 2003

AbstractOn irradiation with ultraviolet light, dialkyl‐4‐hydroxyphenylsulfonium salts undergo reversible photodissociation and in the process generate ylids and Brønsted acids. When the anions are nonnucleophilic in character, as, for example, BF4−, AsF6−, PF6−, and SbF6−, the strong acid which is produced is capable of initiating cationic polymerization. The polymerization of several monomers was carried out to demonstrate the general applicability of these new photoinitiators.
The synthesis and thermal polymerization of 4,4′‐diethynylphenyl ether
Authors: Ratto J. J. , Dynes P. J. , Hamermesh C. L. 
Published: April 2003

AbstractDiethynylphenyl ether (DEPE) was synthesized and its thermal polymerization studied by NMR, IR, and DSC techniques. DEPE is a crystalline solid that melts at 72–73°C and undergoes polymerization beginning at about 150°C. The heat of polymerization measured by DSC was 53 ± 2 kcal/mole. Thermomechanical analysis (TMA) of the fully cured resin showed softening behavior at temperatures in excess of 400°C. Weight loss up to 720°C was only 21%. A mechanism of polymerization based on the analysis of IR and NMR data for party polymerized material below 300°C is proposed.
N‐methyl‐substituted aromatic polyamides
Authors: Greenwood Thomas D. , Kahley Richard A. , Wolfe James F. , Clair Anne St. , Johnston Norman J. 
Published: April 2003

AbstractA series of N‐methyl‐substituted aromatic polyamides derived from the secondary aromatic diamines 4,4′‐bis(methylamino)diphenylmethane, 3,3′‐bis(methylamino)diphenylmethane, 4,4′‐bis(methylamino)benzophenone or 3,3′‐bis(methylamino)benzophenone and isophthaloyl dichloride, and terephthaloyl dichloride or 3,3′‐diphenylmethane dicarboxylic acid dichloride was prepared by high‐temperature solution polymerization in s‐tetrachloroethane. Compared with analogous unsubstituted and partly N‐methylated aromatic polyamides, the full N‐methylated polyamides exhibited significantly lower glass transition temperatures (Tg), reduced crystallinity, improved thermal stability, and good solubility in chlorinated solvents.
Evolution of aromatic compounds in the thermal decomposition of vinyl polymers
Authors: Ballistreri A. , Foti S. , Montaudo G. , Scamporrino E. 
Published: April 2003

AbstractThe thermal decomposition products that evolve from poly(vinyl chloride) (PVC), poly(vinylbromide) (PVB), poly(vinyl alcohol) (PVA), and poly(vinylacetate) (PVAc) were analyzed by direct pyrolysis in the ion source of a mass spectrometer (MS). Our results indicate that in both stages of the decomposition process which occurred in the four vinyl polymers investigated several aromatic hydrocarbons were produced and that the relative amounts of benzene, napthalene, and anthracene were different in the two stages. This previously unreported information determines in a single scheme the thermal behavior of the title compounds.
Graft copolymerization onto jute fiber: Ceric ion‐initiated graft copolymerization of methyl methacrylate
Authors: Huque M. M. , Habibuddowla Md. , Mahmood A. J. , Mian A. Jabbar 
Published: April 2003

AbstractGraft copolymerization of methyl methacrylate (MMA) was carried out on both defatted and bleached jute fibers using ceric ammonium sulfate (CAS) as the initiator. In order to obtain the optimum condition for grafting, the effects of initiator concentrations, temperature, time of reaction, lignin content of jute, and the monomer concentration were studied. The maximum percent grafting and grafting efficiency were found to be 132% and 0.71, respectively. Kinetic studies showed that at 0.03M CAS, the reaction appeared to obey the second‐order process. The activation energies were found to be 7.74 and 5.12 kcal/mole for defatted (lignin content, 15.7%) and chlorite‐bleached jute (lignin content 10%), respectively. The activation energies of graft copolymerization of MMA onto jute fiber are compared with the energies of activation of graft copolymerization of acrylonitrile (AN).
Stereochemistry in cationic polymerization of alkenyl ethers. V. Stereochemistry of acetal additions as model reactions for the polymerization of alkenyl ethers
Authors: Higashimura Toshinobu , Hirokawa Yoshitsugu , Matsuzaki Kei , Uryu Toshiyuki 
Published: April 2003

AbstractAcetal additions to β‐substituted vinyl ethers having a variety of substituents (alkenyl ethers) were stereochemically investigated as model reactions for their cationic polymerization. The reactions catalyzed by BF3O(C2H5)2 in CH2Cl2 at O°C gave 1:1 adducts, the steric structure of which was determined by means of 13C‐NMR spectroscopy. trans‐Alkenyl ethers always gave adducts with a single structure stereospecifically, indicating that the intermediate carbocation attacks a trans‐alkenyl ether from a definite direction independent of the bulkiness of substituents. On the other hand, cis‐alkenyl ethers formed adducts with two steric structures, and the direction of cation addition was found to depend on the bulkiness of the alkoxy group involved. The above trends were in agreement with the results for poly(alkenyl ether)s and allowed detailed discussion of the stereochemistry of the propagation processes in alkenyl ether polymerizations.
Monte Carlo‐studium der ireversiblen terpolymerisation: Das modell und anwendungen
Authors: Moţoc I. , Muşcutariu I. , Holban St. , Dragomir O. 
Published: April 2003

AbstractThe Monte Carlo model of the ternary irreversible copolymerization is presented. The computer program MEMøRY‐4, which implements the described model, is used to study the methyl methacrylate/methyl acrylate/maleic anhydride, butadiene/styrene/2‐methyl‐5‐vinylpyridine, and styrene/methacrylonitrile/α‐methyl styrene terpolymers. One discusses the problem of transferability of reactivity ratios determined for binary copolymerizations to the ternary ones. It can be concluded that the transferability is not assured, but using only composition data it is difficult to achieve a safe conclusion (Fisher statistics).
Peroxo salts as initiators of vinyl polymerization. IV. Polymerization of methacrylamide initiated by peroxodisulfate ion and metal ion catalysis
Authors: Manickam S. P. , Subbaratnam N. R. , Venkatarao K. 
Published: April 2003

AbstractThe polymerization kinetics of methacrylamide (M) initiated by S2O ion in the presence and absence of the metal ions Ag+ and Cu2+ has been studied. The rate laws have been established and are compared with those of acrylamide. The results indicate that steric hindrance from the α‐methyl group affects the initiation reaction. Cu2+ ions are found to reduce the rate of polymerization.
Head‐to‐head polymers. XV. A facile synthesis of 2,3‐disubstituted succinates and butanediols‐1,4
Authors: Yamada A. , Grossman S. , Vogl O. 
Published: April 2003

AbstractA synthetic approach that makes symmetrically 2,3‐dialkyl‐substituted succinates and compounds prepared from 2,3‐dialkyl‐substituted succinates easily available has been developed. Coupling of α‐bromoalkanoic esters with a zinc/copper couple produced in about 40% yield 2,3‐disubstituted succinates which were reduced with LiAlH4 to 2,3‐disubstituted butanediols‐1,4 in nearly quantitative yields. Some 2,3‐disubstituted butanediols‐1,4 were cyclodehydrated under reduced pressure with KHSO4 to 3,4‐disubstituted tetrahydrofurans or acetylated and the diacetyl compounds pyrolyzed at 525°C to 2,3 disubstituted butadienes‐1,3. The length of the alkyl chains of the 2,3‐dialkylsuccinates and consequently the 2,3‐dialkylbutanediols‐1,4 ranged from C2 to C16. 2,3‐Disubstituted butanediols‐1,4, 2,3‐disubstituted butadienes‐1,3, and 3,4‐disubstituted tetrahydrofurans are interesting monomers for polymerization experiments.