bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methylene‐bridged aromatic polyesters. Synthesis, characterization, and radiation‐induced crosslinking
Authors: Havens Stephen J. , Bell Vernon L. 
Published: April 2003

AbstractAromatic polyesters connected by methylene groups were synthesized. Two pairs of aromatic diacid chlorides, 3,3′‐methylenedibenzoyl chloride and 4,4′‐methylenedibenzoyl chloride were each polymerized via interfacial polycondensation with 2,2‐bis(4‐hydroxyphenyl)propane (bisphenol A), 3,3′‐methylenediphenol, and 4,4′‐methylenediphenol. For comparison, 3,3′‐carbonyldibenzoyl chloride and 4,4′‐carbonyldibenzoyl chloride were similarly polymerized with bisphenol A. Substitution of meta,meta' oriented phenylene groups for para,para' oriented phenylene groups had a significant and cumulative effect in reducing the glass transition temperatures of the polymers, thereby enhancing their processability. In air the methylene groups of the polyesters undergo oxidation and crosslinking at elevated temperatures. Electron beam irradiation of thin films of the methylene‐linked polyesters at room temperature resulted in some chain extension and crosslinking, as evidenced by increased solution viscosity and gel formation. Irradiation at a temperature near or above the glass transition temperatures of the polymers greatly enhanced the tendency for the polymers to crosslink.
Amino acid end‐group in commercial heparin. I. Determination of the number of amino and hydroxyl end groups in heparin
Authors: Arai Kozo , Nakamura Yoshio , Edwards H. E. , Phillips G. O. 
Published: April 2003

AbstractThree commercial heparins of different molecular weights and anticoagulant activities were dinitrophenylated (DNP) with 2,4‐dinitrofluorobenzene under aqueous conditions. The absorption spectra observed for DNP heparins in a 1% NaHCO3 solution consisted of the two absorption spectra characteristic of DNP—amino (N—DNP) and DNP—hydroxyl (O—DNP) groups. The number of N—DNP, O—DNP, and (N + O)—DNP groups were determined as well as the number of N—DNP groups per heparin chain; different values (i.e., 0.16, 0.17, and 0.55) for the latter were obtained with the three heparins. Further calculations showed that two of the heparins had approximately two (N + O)—DNP groups per chain (i.e., 2.1 and 1.8) whilst the third sample, considered to be a “cruder” heparin, had a value of 1.4.
ESR studies on radical polymerization of vinyl ethers
Authors: Kamachi Mikiharu , Tanaka Kohji , Kuwae Yoko 
Published: April 2003

AbstractESR studies on the radical polymerization of vinyl ethers were performed from −50°C to room temperature using di‐tert‐butylperoxide as a photoinitiator. Well resolved ESR spectra were assigned to propagating radicals of vinyl ethers. Their hyperfine splitting constants due to α‐proton were about 16 G, being smaller than those of ethyl acrylate and vinyl acetate. The smaller constants is ascribed to a deviation of the propagating radicals from sp2 hybrid structure. The reason why high polymers are not obtained from vinyl ethers by radical polymerization is discussed on the basis of information from the ESR studies.
Preparation and characterization of aromatic copolyesters containing the o,o′‐biphenylene ring system
Authors: Polk Malcolm B. , Kannappan Venu , Harruna Issifu , Phingbodhipakkiya Metha 
Published: April 2003

AbstractPoly[oxy‐2,2′‐diphenyleneoxyisophthaloyl‐b‐oxy(2‐methyl‐1,3‐phenylene)oxyterephthaloyl] I, poly[oxy‐2,2′‐diphenyleneoxyterephthaloyl‐b‐oxy(2‐methyl‐1,3‐phenylene)oxyterephthaloyl] II, poly(oxy‐2,2′‐diphenyleneoxyisophthaloyl‐b‐oxy‐2,2′‐diphenyleneoxyterephthaloyl) III, poly[oxy‐2,2′‐diphenyleneoxyterephthaloyl‐b‐oxy(2‐methyl‐1,4‐phenylene)oxyterephthaloyl] IV, poly[oxy2,2′‐diphenyleneoxyterephthaloyl‐b‐oxy(2‐chloro‐1,4‐phenylene)oxyterephthaloyl] V, poly[oxy‐2,2′‐diphenyleneoxyterephthaloyl‐co‐oxy(2‐chloro‐1,4‐phenylene)oxyterephthaloyl] VI, and poly[oxy‐2,2′‐diphenyleneoxyterephthaloyl‐co‐oxy(2‐methyl‐1,4‐phenylene)oxyterephthaloyl] VII have been synthesized and characterized. Random copolyester VI appears to form a birefringent fluid phase above the melting temperature.
Extended cooperative electronic effects in poly((E,E)‐[6.2]paracyclophane‐1,5‐diene)
Authors: Glatzhofer Daniel T. , Longone Daniel T. 
Published: April 2003

AbstractFluorescence spectroscopy of poly((E,E)‐[6.2]paracyclophane‐1,5‐diene) shows the existence of several emission maxima which appear at wavelengths longer than that of the [3.2]paracyclophane repeat‐unit excimer. These maxima appear to be emission bands due to “extended excimer” fluorescence from multiples of electronically interacting repeat units. Oxidation of the polymer by exposure to iodine vapor results in a material which exhibits a strong, asymmetric electron‐spin‐resonance spectrum with g = ca. 2.00 and a DC conductivity of 5 X 10—4 S‐cm—1. These results are interpreted by a model in which segments of interacting radical cation salts occur pendant to and along the polymer chains but are of random length and orientation in the bulk polymer. Similar results were obtained for a structurally related polymer containing [3.3]paracyclophane rings.
Functional polymers and sequential copolymers by phase transfer catalysis. 18. Synthesis and characterization of α,ω‐bis(2,6‐dimethylphenol)–poly(2,6‐dimethyl‐1,4‐phenylene oxide) and α,ω‐bis(vinylbenzyl)–poly(2,6‐dimethyl‐1,4‐phenylene oxide) oligomers
Authors: Nava Hildeberto , Percec Virgil 
Published: April 2003

AbstractA novel and convenient synthetic method for the preparation of α,ω‐bis(2,6‐dimethylphenol)–poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO‐2OH) is presented. It is based on the oxidative copolymerization of 2,6‐dimethylphenol (DMP) with 2,2′‐di(4‐hydroxy‐3,5‐dimethylphenyl propane) (TMBPA) in a mixture of water–methanol or chlorobenzene–methanol. By using a 4/1 mole ratio of DMP to TMBPA and different solvent mixtures, it was possible to obtain bifunctional PPO‐2OHs with number average molecular weights between 1000 and 5000. A phase‐transfer‐catalyzed etherification of PPO‐2OH chain ends with a mixture of m‐ and p‐chloromethylstyrene was used to synthesize α,ω‐bis(vinylbenzyl)‐poly(2,6‐dimethyl‐1,4‐phenylene oxide)s (PPO‐2VBs). The thermal polymerization of the PPO‐2VBs was studied by differential scanning calorimetry, and has demonstrated a very high thermal reactivity for this new class of reactive oligomers.
Rhodium and platinum complexes as catalysts for the polymerization of phenylacetylene
Authors: Furlani A. , Licoccia S. , Russo M. V. , Camus A. , Marsich N. 
Published: April 2003

AbstractIn polymerization reactions of phenylacetylene three different types of polyphenylacetylene (PPA) were prepared by using Rh and Pt complexes as catalysts in different reaction conditions. Type I PPA is obtained with [Rh (COD) Chel] PF6complexes (COD =cis,cis‐cycloocta 1,5‐diene; chel = 2,2′‐bipyridine, 1,10‐phenanthroline, 2,9‐dimethyl‐1,10‐phenanthroline, 5,6‐dimethyl‐1,10‐phenanthroline, 3,4,7,8‐tetramethyl‐1,10‐phenanthroline) in bulk, benzene methanol, while type II PPA is obtained with the same catalysts inp‐dioxane and type III PPA in the presence of [Pt (CCPh)2(PPh3)2] in bulk. Type I, II, and III PPA exhibit different IR and1H‐NMR spectra, which have been compared with literature data. Correlations proposed by different Authors between spectral properties of PPA and chain structures are also discussed.
Spectroscopic studies on the oligomers of bromotrifluoro ethylene
Authors: Rao M. Rama , Radhakrishnan T. S. , Ravindran P. V. 
Published: April 2003

AbstractThe photo‐initiated oligomerization of bromotrifluoroethylene in chlorotrifluoromethane medium was found to yield a complex mixture of products. 19F‐nmr, infrared and GC‐MS spectra revealed the presence of ‐CF2Br and —CF = CF2 and the absence of —CF Br2 and —CF3 end groups in the products. Oligomers up to pentamers were identified and their structures elucidated by GC‐MS. A plausible mechanism for their formation is suggested.
Photocrosslinkable polyesters with conjugated double bonds: Reciprocity effect in laser recording
Authors: Iwata Kaoru , Hagiwara Tsuneo , Matsuzawa Hiroshi 
Published: April 2003

AbstractThe reciprocity effect under intense illumination was studied with photocrosslinkable polyesters of p‐phenylenebis(α‐cyanobutadiene carboxylic acid) (I), m‐phenylenebis(α‐cyanobutadiene carboxylic acid) (II), and p‐phenylenebis(acrylic acid) (III), with an argon ion laser as a light source. The reciprocal sensitivities of I, II, and III were 5.0, 1800, and > 105 mJ/cm2, respectively. II and III required sensitization to enhance their sensitivities to a level at which reciprocity effects could be measured. I obeyed the reciprocity law over a wide range of exposure times from seconds to microseconds. Both II′, a copolyester of II, and III showed a dramatic decrease of sensitivity in high‐intensity/short‐time exposure when sensitized by 9,10‐phenanthraquinone and pyrylium salts.
Dual‐functional catalysis for ethylene polymerization to branched polyethylene. II. Kinetics of ethylene polymerization with a mixed homogeneous–heterogeneous Ziegler–Natta catalyst system
Authors: Kissin Yury V. , Beach David L. 
Published: April 2003

AbstractThe previous paper in this series described several catalytic systems which can be used for simultaneous ethylene dimerization to 1‐butene and copolymerization of the in situ‐formed olefin with ethylene to form branched polyethylene. Such catalytic systems allow the synthesis of linear low‐density polyethylene from a single monomer source. This article presents a more detailed description of one of the dual‐functional catalyst systems studied, a mixed homogeneous–heterogeneous Ziegler–Natta catalyst, Al(C2H2)3–Ti(Oi‐C3H7)4–TiCl4/MgCl2/polyethylene, at 90°C. Discussed are kinetics of ethylene dimerization with the soluble component, Al(C2H5)3–Ti(Oi–C3H7)4, and the effects of aluminum alkoxides on the system. Addition of the ethylene dimerization catalyst to the solid component, Al(C2H5)3–TiCl4/MgCl2/polyethylene, results in a partial decrease in polymerization activity. Some of the decrease can be attributed to the presence of 1‐butene in the reaction medium. Measurement of the reactivity ratio kEE/kEB for two catalytic systems, the solid component and the title dual‐functional catalyst, demonstrated that the presence of the dimerization component results in a twofold increase in the reactivity ratio, from 20 to ca. 40.
Kinetics of thermal depolymerization of trimethylsiloxy end‐blocked polydimethylsiloxane and polydimethylsiloxane‐N‐phenylsilazane copolymer
Authors: Kang D. W. , Rajendran G. P. , Zeldin M. 
Published: April 2003

AbstractThe thermal degradation of Me3SiO end‐blocked polydimethylsiloxane (eb‐PDMS) and polydimethylsiloxane‐N‐phenylsilazane (eb‐PDMS–NPhSz) copolymer was studied. For both polymers relative degree of polymerization (DP/DP0) as a function of conversion (1 – W/W0) data were obtained. For eb‐PDMS the results were consistent with a mechanism involving a rate determining random siloxane bond cleavage initiation step followed by a rapid and complete depropagation of the active fragments evolving volatile cyclic oligomers. Rate constants (k) for initiation were obtained at four temperatures from plots of DP−1 vs. time. An Arrhenius activation energy of approximately 80 kcal/mol was determined and is consistent with a SiOSi scission transition state. The degradation of eb‐PDMS–NPhSz appears to follow the same depolymerization process evolving cyclic oligomers. Although DP/DP0 vs. C data suggest a random cleavage–complete depolymerization mechanism, an Arrhenius plot suggests a more complex degradation mechanism. The role of impurities as degradation catalysts is discussed.
Degradation of dehydrochlorinated poly(epichlorohydrin) using photo‐generated cationic catalysts
Authors: Nishikubo Tadatomi , Iizawa Takashi , Sugawara Yoshihiko , Shimokawa Tsutomu 
Published: April 2003

AbstractThe photochemical reaction of polymer containing vinyloxy group (P‐1), which was prepared from treating poly(epichlorohydrin) with base using a phase transfer catalyst, was investigated in the presence of a photo‐generated cationic catalyst (PGCC). When the polymer with PGCC was irradiated, the vinyloxy group in the polymer disappeared rapidly. The rate of disappearance of the vinyloxy group in P‐1 was strongly influenced by its content in the polymer and the kind of PGCC. P‐1, containing about 65 mol% of vinyloxy group, had the highest photochemical reactivity, and PGCC with PF6− and SbF6− as counterions showed higher catalytic activity than those with BF4− The photochemical reaction of P‐1 involved a number of reactions such as degradation, rearrangement, and crosslinking reaction competitively; however, P‐1 with less vinyloxy group than 60 mol% degraded preferentially. These results suggested that P‐1 is an excellent photodegradating polymer using PGCC. The thermal degradation of P‐1 was also investigated.
Wholly aromatic polyamide‐hydrazides. IV. Structure–property relationships for polymers containing p‐phenylene and m‐phenylene units
Authors: Dvornic Petar R. 
Published: April 2003

AbstractA series of wholly aromatic polyamide‐hydrazides was investigated in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as chain flexibility, membrane permselectivity, and thermal as well as thermo‐oxidative stability. For that reason, the content of para and meta phenylene units was varied within this series so that the changes in the latter were 12.5 mol % from polymer to polymer, starting from an overall content of 0–50 mol %. The polymers were prepared by a low‐temperature solution polycondensation reactin of p‐aminobenzhydrazide (ABH) and terephthaloyl chloride (TCI), isophthaloyl chloride (ICI), and their appropriate combinations in N,N‐dimethylacetamide (DMA) as solvent and all of these preparations were monitored viscometrically in order to prepare the products with as similar as possible average molecular weights. Polymer structures were characterized by elemental analysis, infrared spectrometry, and 13C NMR spectroscopy, while their molecular weights were determined by light scattering and dilute‐solution viscometry. Polymer properties were evaluated by solution viscometry, reverse osmosis tests, and thermal gravimetric analysis. The results obtained during the preparation of these materials, their subsequent structural characterization, and their property evaluations are discussed. They clearly indicate that substitution of m‐phenylene units for p‐phenylene ones within this polymer series led to an increase in polymer chain flexibility (from what is usually referred to as semiflexible or semirigid to typically flexible macromolecules), disrupted selectivity of the asymmetric thin membranes under reverse osmosis conditions and decreased stability at elevated temperatures in inert as well as in oxidative atmospheres.
Effects of chemical structure on low‐temperature modulus for UV‐curable polybutadiene acrylates as an optical fiber coating material
Authors: Kimura T. , Yamakawa S. 
Published: April 2003

AbstractThe relationship between chemical structure and low‐temperature modulus of ultraviolet(UV)‐radiation‐cured optical‐fiber coating materials has been investigated. The coating materials are low‐viscosity liquid compounds consisting of a 1,4‐polybutadiene diacrylate oli‐gomer, a monomer, and a photoinitiator. Dynamic mechanical test results show that low‐temperature modulus and glass transition temperature (Tg) are affected by the monomer structure and monomer concentration in the coating material in cases where the same oligomer is used. With increasing alkyl group chain length of the alkylacrylate monomer, the Tg value is shifted to lower temperatures. Low‐temperature modulus increases with increasing monomer concentration in the coating material. Low‐temperature excess optical losses of coated fibers have been found to be closely related to low‐temperature modulus of the coating.
A pyrolysis/GC/MS study of plasma‐polymerized toluene—evidence for carbon atom scrambling in the plasma
Authors: Kaplan S. , Dilks A. , Crandall R. 
Published: April 2003

AbstractMass spectral analysis of the gas‐chromatography‐separated pyrolysis products of the solid polymer formed in a toluene plasma has shown the presence of a number of phenyl‐containing structures. Of particular interest is the biphenyl product, whose isotopic distribution patterns are very different for the polymers prepared from natural 13C abundance and 13CH3‐labeled toluene. This result is interpreted in terms of carbon atom scrambling via seven‐membered‐ring intermediates in the gas phase during plasma polymerization. A comparison of measured isotopic patterns with calculated patterns reveals that 34 ± 10% of the toluene molecules scramble prior to polymer formation. This value is similar to an upper bound on scrambling determined here but based on earlier NMR results1 and reinforces a model for the structure of plasma‐polymerized toluene established in that work.
Diacetylenic liquid‐crystalline polymers and copolymers. I. Derivatives of diphenyldiacetylene
Authors: Ozcayir Y. , Blumstein A. 
Published: April 2003

AbstractThe diphenyldiacetylene moiety is highly mesogenic and liquid‐crystalline mesophases were observed in polymers incorporating such moieties in the main chain of polyesters with regularly alternating mesogenic groups and flexible spacers. Extensive crystallinity, polymorphism and high values of transition temperatures characterize these polymers. The reactivity of the conjugated triple bond at the temperature of mesophase formation impedes the stability of LC mesophases. Methyl substitution in the benzene ring lowers the transition temperatures significantly.
Photochemically active modification of polymers I. Preparation and reaction of photocrosslinkable poly(vinyloxycarbonylchalcone)
Authors: Watanabe Shoji , Harashima Susumu , Tsukada Noriaki 
Published: April 2003

AbstractPhotocrosslinkable polymers containing pendant chalcone groups were prepared by the reaction of 4′‐substituted‐4‐carboxychalcone (4‐R‐CC) with poly(vinyl alcohol) (PVA) in homogeneous dimethylacetamide (DMA) solutions using 2,4,6‐trinitrochlorobenzene (TNCB) as condensing agents. The mechanism of ester formation is mainly discussed for 4‐carboxychalcones on the basis of the isolated intermediates and mass spectrometry. The modified polymers showed excellent properties as photocrosslinkable polymers and the photosensitivity was confirmed in the range of about 1 to 5 mJ/cm2.
Polydimethylsiloxane–vinyl block polymers. II. The synthesis and characterization of block polymers by the thermolysis of polydimethylsiloxane macroinitiators containing bis(silyl pinacolate) groups
Authors: Crivello J. V. , Lee J. L. , Conlon D. A. 
Published: April 2003

AbstractThe thermolysis of polydimethylsiloxanes containing thermally labile bis(silyl pinacolate) groups in the backbone in the presence of various vinyl monomers leads to the direct synthesis of block polymers. Depending on the monomer chosen, simple triblock or multisequence block polymers can be readily prepared. Analysis of the products of the block polymerizations using various styrenic‐type monomers shows that only block polymers are obtained, i.e., no homo‐polymers are formed. These block polymers display evidence of phase separation such as intense iridescence and solvent‐dependent mechanical properties. The mechanical properties of these block polymers have been measured and found to be highly composition dependent. Depending on the block length and the relative portions of the hard (vinyl) and soft (polydimethylsiloxane) blocks, one can produce either thermoplastic elastomers or rubber‐modified thermoplastics.
Polymerization of vinyl chloride at reduced monomer accessibility. III. Polymerization kinetics and molecular structure using PVC latex as seed
Authors: Hjertberg Thomas , Sörvik Erling M. 
Published: April 2003

AbstractVinyl chloride was polymerized at 53–97% of the saturation pressure in a water‐suspended system at 55°C with an emulsion PVC latex as seed. A water‐soluble initiator was used in various concentrations. The monomer was continuously charged as vapor from a storage vessel kept at lower temperature. Characterization included determination of molecular weight distribution and degree of long‐chain branching by gel chromatography and viscometry and by thermal dehydrochlorination. To avoid diffusion control intense agitation was necessary. At a certain conversion, aggregation of primary particles resulted in restricted polymerization rate. Before aggregation, formation of new particles did not occur as the number of particles was high enough to ensure capture of all oligoradicals. The kinetic equation accepted for ordinary emulsion polymerization of vinyl chloride was qualitatively found to be valid after the pressure drop as well. Decreased termination rate may result in increased polymerization rate at reduced monomer concentration, i.e., a gel effect, especially at low particle numbers and high polymer contents. The molecular weight decreased with decreasing monomer concentration. This is in accordance with the new mechanism suggested for chain transfer to monomer starting with occasional head‐to‐head additions.
Poly(alkyl α‐bromoacrylate)s. III. Tacticity analysis from 19 mHz 13C‐NMR spectroscopy
Authors: Saunders K. G. , Macknight W. J. , Lenz R. W. 
Published: April 2003

AbstractPolymer tacticity was determined by 19 mHz 13C‐NMR spectroscopy for isotactic, atactic, and syndiotactic samples of six poly(alkyl α‐bromoacrylate)s. Included in this series were the methyl, ethyl, n‐propyl, i‐propyl, n‐butyl, and n‐pentyl esters. Complete assignments for the 10 pentad peaks of the carbonyl carbon resonance were achieved for all but the i‐propyl ester while a complete analysis of tetrad tacticity from the backbone methylene carbon resonance was possible for all but the methyl ester. The tetrad values calculated from the experimentally determined pentad contents were found to agree with the experimental tetrad values. As a result of insufficient peak separation of the quaternary carbon resonance, complete pentad assignments were possible in only a few instances. The polymerization reaction mechanisms were discussed in terms of the propagation statistics calculated from the experimentally determined tetrads and pentads. Both the atactic and syndiotactic polymers that were synthesized by free radical techniques displayed Bernoullian or random statistics while the stereochemical statistics of the isotactic polymers synthesized by a modified Grignard complex were more consistent with nonrandom or first‐order Markovian statistics.
Preparation of plasma‐films containing carboxylate anions by hydrolysis with octylbromide
Authors: Inagaki N. , Oh‐Ishi K. 
Published: April 2003

AbstractTo obtain thin films containing carboxylate anions, hydrolysis of amido groups in films plasma‐polymerized from trimethylsilyldimethylamine (TMSDMA) and bis(dimethylamino)methylvinylsilane (BDMAMVS) has been investigated by infrared spectroscopy and ESCA. The thin films from TMSDMA and BDMAMVS were hydrolyzed at 80–100°C for 3–16 h to transform amido groups to carboxyl groups. The products hydrolyzed from the TMSDMA–plasma‐polymers were mixtures of carboxylate ester and carboxylic acid, and that from the BDMAMVS–plasma‐polymers was carboxylic acid. The hydrolysis reaction was restricted at regions near polymer surfaces.
Synthesis of bifunctional monodisperse poly(N‐isovaleryl ethyleneimine)
Authors: Swamikannu A. Xavier , Hsiue Ging‐Ho , Litt Morton H. , Balasubramanian M. 
Published: April 2003

AbstractA bifunctional initiator, ethanediyl 1,2‐bis(2‐isobutyl oxazolinium trifluoromethane sulfonate) was prepared and used for the ring opening polymerization of 2‐isobutyl oxazoline. Polymerizations were run in CH3CN at 80 and 60°C and in sulfolane at 80°C. The molecular weight distributions of the poly(N‐isovaleryl ethyleneimine)s produced, M/I ≤ 45, approached Poisson distribution.