bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transitions in trans‐1,4‐polyisoprene
Authors: Lovering Edward G. , Wooden David C. 
Published: April 2003

AbstractThe melting transitions of both crystalline forms of trans‐1,4‐polyisoprene, as detected by differential thermal analysis, have been identified by attendant studies with optical microscopy and x‐ray diffraction. The lower‐melting (LM) form melts initially at a temperature which depends upon the crystallization temperature but which, under our experimental conditions, is between 45 and 53°C. If recrystallization is allowed to occur, the apparent final melting point, which depends upon the recrystallization temperature, is about 58°C. The initial melting point of the higher‐melting (HM) form, also crystallization temperature‐dependent, is upwards of 57°C. Under the most easily accessible experimental conditions, it may be obscured by the final melting of the LM‐form. The apparent final melting point of the HM form is approximately 66°C. Conversion of the LM form into the HM form occurs only by fusion and crystallization. No evidence of a solid‐solid transition was found. The rate of conversion is governed principally by the rate of nucleation at the conversion temperature. If fusion of the LM form is incomplete, recrystallization of the LM form takes place instead of conversion to the HM form.
Viscoelastic properties of crosslinked solutions of poly(β‐hydroxyethyl methacrylate) in diethylene glycol. II. Dependence of creep compliance on concentration in the rubbery zone
Authors: Janáček Josef , Ferry John D. 
Published: April 2003

AbstractCreep compliance data, J(t), at 35°C for poly(β‐hydroxyethyl monomethacrylate), crosslinked by ethylene glycol dimethacrylate in a range of concentration C from 0.0855 to 2.053 × 10−4 mole/cm3 and swollen to various degrees in diluents, were examined for time‐concentration superposition. From the dependence of time scale shift factors on v2, the volume fraction of polymer, free volume parameters were calculated for two samples with C = 0.0855 × 10−4 and 0.136 × 10−4 mole/cm3, swollen in the range of v2 from 0.134 to 0.591. Special attention was given to the magnitude of the shift factor on the log J(t) axis and its dependence on concentration, which was found to depend substantially on the crosslinking and the swelling degrees of the samples. This shift was approximately log v2 for lightly crosslinked samples, swollen to a small degree, measured in the neighborhood of the main transition. For higher degrees of crosslinking and/or swelling, the shift was much less and for the most highly crosslinked networks swollen to equilibrium it was even negative. The correction appears to be very sensitive to the strain of the effective chains and to the location on the time scale with respect to the transition and rubberlike zones of viscoelasic behavior. It was found that the parameters of the WLF equation calculated in our previous study from the time‐temperature superposition of the creep curves in the rubber‐glass transition are valid also for the rubberlike region.
Temperature dependence of relative modulus in filled polymer systems
Authors: Nielsen Lawrence E. , Lewis Thomas B. 
Published: April 2003

AbstractThe temperature dependence of relative modulus observed in filled thermoset, thermoplastic, and polyelectrolyte salt matrices is explained on the basis of induced stresses produced by the differences in the thermal expansion coefficients of the constituent materials. The analysis is based on the assumption that the modulus of the matrix in a filled polymer is less than that of the unfilled polymer. The temperature dependence of relative modulus is expressed as a function of the difference in thermal expansion coefficients, the volume fraction, the relative modulus in the unstressed state, and mechanical properties of the phases. Agreement is good between the analysis and experimental results for three systems: epoxy and glass, polyethylene and wollastonite, and a polyelectrolyte salt with mica and asbestos.
Electron spin resonance study on homogeneous catalysts derived from n‐butyl titanate and triethylaluminum
Authors: Hirai Hidefumi , Hiraki Katsuma , Noguchi Isamu , Makishima Shoji 
Published: April 2003

AbstractESR spectra of homogeneous catalyst systems derived from n‐butyl titanate and triethylaluminum at Al/Ti molar ratios of 1.0–10 were observed in toluene solution at several temperatures from −78°C to +25°C. In the whole range of Al/Ti molar ratios, a single signal with a g value of 1.951 was observed at −78°C and was associated with the first reaction intermediate. With increasing temperature, the intensity of the signal decreased gradually, while two series of signals appeared, depending on the Al/Ti molar ratio. At an Al/Ti molar ratio of 1.7, seven kinds of signals with g values of 1.960, 1.946, 1.950, 1.959, 1.980, 1.977, and 1.978, respectively, were observed. On the other hand, four kinds of signals with g values of 1.934, 1.966, 1.952, and 1.979, respectively, were found at Al/Ti molar ratios larger than 3. The structures of the species corresponding to the signals were discussed on the basis of the ESR spectra, the order of their growth and their hyperfine structures being considered. Two series of ESR signal were correlated to two kinds of active species for polymerization of styrene and butadiene, respectively.
Hydrolytic polymerization of caprolactam. I. Hydrolysis—polycondensation kinetics
Authors: Giori C. , Hayes B. T. 
Published: April 2003

AbstractIn a study aimed at process optimization of caprolactam polymerization, particular reference has been paid to the competing role of water in caprolactam hydrolysis and endgroup polycondensation. The dependence of the apparent equilibrium constant for polycondensation on water concentration indicated that there is a strong effect of the medium on the activities of the reacting species which can not be neglected in a kinetic study of the polycondensation reaction. The effect of a variation of the medium was taken into account by using a polycondensation rate constant which included a function of the water present at any given time. With the aid of analog computer curve‐fitting techniques, good agreement with second‐order kinetics was found. The validity of a second‐order mechanism was confirmed in a kinetic study of the chain amide linkage hydrolysis. The hydrolysis of caprolactam follows substantially different kinetics, where the generation of carboxyl groups reduces the activation energy of the reaction, which follows predominantly a third‐order mechanism.
Poly(ester‐acetals) from geometric isomers of methyl azelaaldehydate glycerol acetal
Authors: Lenz Robert W. , Awl R. A. , Miller W. R. , Pryde E. H. 
Published: April 2003

AbstractThe glycerol acetal of methyl azelaaldehydate is an ω‐hydroxy ester that exists as a mixture of dioxolanyl and dioxanyl isomers, each having two geometric isomers. Each of the four isomers was isolated by chromatographic (gas–liquid and column) and fractionating (crystallization and distillation) methods. Structural assignments were made on the basis of nuclear magnetic resonance and infrared spectral data. Linear poly(ester‐acetals) were prepared from each of the cis and trans forms of the dioxanyl isomers and from a mixture of the dioxolanyl geometric isomers. Physical properties of these polymers were correlated with their structures. When prepared with basic condensation catalysts, the polymers retained the geometric configuration and structural identity of the monomer. When prepared with lead acetate, structural rearrangement as well as polycondensation occurred, resulting in an enrichment of the dioxolanyl isomer and simultaneous increase in polymer crystallinity. The enrichment took place at elevated temperatures and also, unexpectedly, at room temperature upon long standing of the polymer. Isomer redistribution at room temperature appears to be antithermodynamic in the reaction sense, yielding a polymer of unusually high dioxolanyl unit content. The driving force for this isomerization may be crystallization of these units by a phenomenon termed a “crystallization‐induced reaction.”
Phosphorus‐containing polyurethans
Authors: Dyer Elizabeth , Dunbar Richard A. 
Published: April 2003

AbstractPhosphorus‐containing polyurethans of the formula
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were prepared by interfacial polymerization of 1,4‐butanebischloroformate and p‐xylylene‐α, α‐bischloroformate with bis(m‐aminophenyl)alkylphosphine oxides. The polymers had number average molecular weights up to 8600. A test of the stability to alkali of one of the polymers (RCH3, X1,4‐C6H4) showed it to be as resistant as nonphosphorus analogs, and a film of this polymer exhibited self‐extinguishing properties. Thermal degradation of the phosphorus polymers, which began at approximately 230°C, occurred by an initial first‐order process, releasing chiefly carbon dioxide. The energies of activation for the maximum rates of weight loss were 31–37 kcal/mole.
A proposal on the steric course of propagation in the homogeneous cationic polymerization of vinyl and related monomers
Authors: Kunitake Toyoki , Aso Chuji 
Published: April 2003

AbstractA stereochemical scheme of propagation was proposed for polymerizations of vinyl and related monomers by Friedel‐Crafts catalysts. For the cationic propagation proceeding via the simple carbonium ion pair, the following two factors were considered to be of primary importance in determining the steric course of propagation: (1) the conformation of the last two units of the propagating polymer segment and the direction of approach of the incoming monomer; (2) the tightness of the growing ion pair. Thus, the front‐side (less hindered site) attack to the carbonium ion gives rise to a syndiotactic placement and the back‐side attack an isotactic placement. The present model can satisfactorily explain the effects of substituents, catalysts, polymerization media, and polymerization temperature on the steric structure of polymers in cationic polymerization of vinyl ethers. Extension of the scheme to polymerization of the β‐substituted vinyl ethers in nonpolar solvents predicts formation of the diisotactic structures consistent with the experimental result. The influences of the polymerization condition on the steric structure of polymer were studied for cationic polymerizations of α‐methylstyrene at low temperatures. Highly syndiotactic polymers were obtained for homogeneous reactions in toluene‐rich media. The isotactic unit increased by increasing the content of methylcyclohexane in the solvent mixture. The effect of catalysts, though insignificant in toluene‐rich media, was clearly noted in methylcyclohexane‐rich media, less active catalysts (e.g., SnCl4) yielding higher amounts of the isotactic unit than more active catalysts (e.g., AlCl3). These results can be readily accommodated in the present model.
Copolymerization with depropagation. III. Composition and sequence distribution from probability considerations
Authors: Howell John A. , Izu Masatsugu , O'Driscoll Kenneth F. 
Published: April 2003

AbstractElementary probability considerations have been used to derive completely general equations which describe both the sequence distributions and compositions to be expected for copolymerizations which follow kinetic models having complete reversibility for all propagation steps. It is shown that previously derived composition equations for both reversible and irreversible systems are special cases of the general equations derived herein.
Polymerization of vinylcyclopropanes. V. Radical copolymerization of 1, 1‐dichloro‐2‐vinylcyclopropane with monosubstituted ethylenes
Authors: Takahashi Takako 
Published: April 2003

AbstractA peculiar copolymer composition equation applicable to the radical copolymerization of 1,1‐dichloro‐2‐vinylcyclopropane with monosubstituted ethylenes was developed. The theory was applied to such ethylenes as methyl acrylate, methyl methacrylate, and styrene. The reactivity ratio parameters which give the best fit to the experimental data were determined.
Endgroup analysis of isolated poly(methyl methacrylate) from graft copolymers of wool
Authors: Arai Kozo , Komine Shigeo , Negishi Michiharu 
Published: April 2003

AbstractIn order to elucidate the termination mechanism in the graft copolymerization of methyl methacrylate to unreduced and reduced wool fibers, graft copolymers were prepared by means of the LiBr–K2S2O8 redox sytem without homopolymer or with K2S2O8 only with homopolymer at 30°C. The graft polymers (PMMA) were isolated almost completely from the wool trunk by an HCI‐digestion method, leaving a few amino acid residues on the end of the graft polymers. Dinitrophenylation of the isolated polymer was carried out by various methods. The spectral features were almost the same as for dinitrophenylated amino acids of the usual type such as valine, leucine, and methionine, with a maximum in ultraviolet light at 340–345 mμ. From colorimetric analysis of the number of dinitrophenylated amino acid endgroups and the measurement of the average molecular weight of the isolated polymers, the number of amino acid endgroups linked to the graft polymers was calculated to be about one and two per polymer chain in reduced and unreduced wool, respectively, independent of the reaction system, graft‐on, and molecular weight of graft polymers. From these facts, it was suggested that the most of isolated polymers are the truly grafted polymers. Also, the termination reactions have been explained as follows. In the unreduced wool, the restriction of mobility of the radical end might be expected, for the confinement of growing chains in wool fibers. This would be favorable to termination by recombination rather than by the disproportionation, since the former has a lower activation energy than the latter. Thus, the formation of intra‐ or intermolecular crosslinks might be considered between polypeptide chains. On the other hand, in the reduced wool, the mobility of graft polymers might be considered to be greater than that of unreduced wool because of its open structure. Therefore, termination would be principally by disproportionation between graft polymer radicals.
Production of organometallic polymers by the interfacial technique. V. Partial mechanistic study of the production of poly[alkyl(aryl)oxysilances]
Authors: Carraher Charles E. , Klimiuk George H. 
Published: April 2003

AbstractA modified interfacial polymerization system capable of producing poly[alkyl(aryl)oxysilanes] consisting of a dichlorosilane in an organic solvent as octane and a diol in 2,5‐hexanedione is presented. It is believed that polymerization occurs near the interface in the dione phase. The products are low to intermediate in molecular weight. As the nature of silane is varied, the rate of polymer formation varies, the silane with the most electron‐deficient silicon giving the greatest rate. Molecular weight is constant as diol is changed but varies when the silane is changed so that the silane with the most bulky substitutes will give polymer with the lowest molecular weight. The results are consistant with a SN2 type reaction mechanism.
Structure of branching in PVC
Authors: Caraculacu A. A. , Bezdadea E. C. , Istrate Gabriela 
Published: April 2003

AbstractA new macromolecular model for branched PVC was synthesized by copolymerization of vinyl chloride with 2,4‐dichloropentene‐1. The composition and the properties of this new copolymer were studied and the phenolysis reaction to determine the content of chlorine atom bound to the tertiary carbon atom (ClT) was carried out. The presence of a longer branch, of PVC type, does not impede the reaction. It is concluded that there are no chlorine atoms at the branching sites in PVC.
Copolymers of vinyl chloride with the vinyl esters and acrylates of low molecular weight polyesters of hydroxyacids
Authors: Chow Roberta C. L. , Marvel C. S. , Magne Frank C. 
Published: April 2003

AbstractVinyl esters and acrylates of polyesters derived from C10−C18 hydroxyacids have been synthesized and copolymerized with vinyl chloride with the hope of achieving an internally plasticized poly(vinyl chloride). Copolymers containing 10–30% polyester are film‐forming materials, and the films cast from THF solutions are generally flexible. A number of these vinyl chloride copolymers with polyesters at approximately 15 and 25% level have been tested for various properties. The internal plasticization is not extensive.
Metal coordination polymers. III. Molecular weights of beryllium phosphinate polymers in chloroform
Authors: Fetter N. R. , Grieve C. M. 
Published: April 2003

AbstractVapor‐phase osmometric molecular weight measurements on beryllium di‐n‐butyl‐phosphinate are in general agreement with the results obtained in chloroform by Ripamonti and co‐workers. The degree of polymer association in anhydrous chloroform is approximately twice that obtained in reagent‐grade chloroform, and the values obtained in both types of chloroform are higher than those obtained by Ripamonti. Membrane osmometric molecular weight measurements on beryllium 4‐biphenyl (phenyl)‐phosphinate in chloroform indicate a reversible degradation exists between a number‐average molecular weight of 170 000 and 30 000, with the value dependent upon the polymer concentration. Treatment of chloroform solutions of this polymer with ammonia prevents reassembly of the polymer from 30 000 to higher values. To explain this and other solution properties of this polymer, a structure is proposed which involves endgroup hydrogen bonding of phosphinate‐bonded aggregates containing approximately 50 monomer units (Mn = 30 000). Under certain conditions, the hydrogen‐bonded aggregates may contain up to 300 monomer units, but in polar solvents such as water or chloroform they are rapidly degraded.
Poly(4,4′‐dipiperidyl)amides
Authors: Preston J. , Smith R. W. 
Published: April 2003

AbstractPolyamides from 4,4′‐dipiperidyl, 1,2‐ethylene‐, and 1,3‐propylene‐ bridged dipiperidyls were prepared via solution and interfacial polycondensation techniques. In sharp contrast to the polyamides from N,N′‐alkyl‐substituted alkylene diamines and aromatic diacids, the polyamides from 4,4′‐dipiperidyls are high‐melting (up to 455°C) and alcohol‐insoluble. Tough films were cast from formic acid solutions of the polymers; fiber of good physical properties was prepared from a formic acid solution of the polyterephthalamide of 1,2‐di(4‐piperidyl)ethane.
Photocycloaddition polymerization. I. Preparation and characterization of poly‐N,N′‐polymethylenebisdichloromaleimides
Authors: De Schryver F. C. , Feast W. J. , Smets G. 
Published: April 2003

AbstractThe benzophenone‐sensitized solution‐phase photocycloaddition polymerization of N,N′‐polymethylenebisdichloromaleimides has been investigated. It is shown that a polymer can be obtained by repeated 2π + 2π photocycloaddition process. The intrinsic viscosity of the products varies from 0.1 to 0.6 when the link between the two maleimide moieties contains more than six and simultaneously an uneven number of methylene units. The polymeric materials form transparent, flexible, noninflammable films and decompose at 310°C.
Synthesis and preliminary evaluation of ordered aliphatic poly(benzoxazole amides),
Authors: De Winter Walter , Stein Ralph , Uwents Henri , Masquelier Camille 
Published: April 2003

AbstractSlightly modified conventional techniques were successfully applied to prepare aliphatic benzoxazolediamines and the corresponding high molecular weight polyamides, which could be spun into excellent fibers. Compared to regular aliphatic polyamides, these products showed higher transition temperatures, improved thermal and light stability, and increased affinity for acid dyes. In addition—quite unexpectedly—these fibers were highly crystalline and oriented after drawing at elevated temperatures.
N,N′‐(disubstitutedmethylene)bisacrylamides: Preparation and polymerization
Authors: Murfin Donald L. , Hayashi Katsumi , Miller Leonard E. 
Published: April 2003

AbstractPreparative methods for the previously unreported N,N′‐(disubstitutedmethylene)‐bisacrylamides are presented. The solubility and thermal stability of these new bisamides are compared to the well known N,N′‐methylenebisacrylamide. N,N′‐Isopropyl‐idenebisacrylamide, one of these new compounds, readily copolymerizes with a variety of vinyl monomers. It forms high molecular weight copolymers by the conjugate polyaddition of alkanedithiols or piperazine.
Equimolecular binary polydines. V. Equibinary poly(cis‐1,4–trans‐1,4)butadiene from bis(π‐allyl nickel trifluoroacetate)
Authors: Marechal J. C. , Dawans F. , Teyssie Ph. 
Published: April 2003

AbstractThe preparation of equibinary poly(cis‐1,4–trans‐1,4)butadiene was investigated in the presence of bis(π‐allyl nickel trifluoroacetate) modified with suitable additional ligands. The behavior of the catalytic species in the polymerization reaction as well as the specific basic properties of the equibinary polybutadiene produced support obviously a regular distribution of the cis and trans isomers in the polymer chains.
N‐vinylthiopyrrolidinone
Authors: Coleman L. E. , Bork J. F. 
Published: April 2003

AbstractThe polymerization reactivity of N‐vinylthipyrrolidinone is described. This monomer readily homopolymerizes and forms copolymers with a wide variety of vinyl monomers. Reactivity ratios in the copolymerization of N‐vinylthiopyrrolidinone with styrene and methyl methacrylate are reported and the Alfrey‐Price Q and e values calculated. These results indicate the high copolymerization reactivity of this monomer in comparison with the oxo‐analog, N‐vinylpyrrolidinone. Some of the results are in conflict with previously reported data.
Irradiation of terephthalophenone in isopropyl alcohol
Authors: Pearson D. E. , Thiemann P. D. 
Published: April 2003

AbstractIrradiation of terephthalophenone in isopropyl alcohol gave a bright yellow‐colored intermediate which decayed rather rapidly. The products were complex and depended upon the mode of irradiation. They ranged from a mixed polymer I to a dimer II. I consisted of about 5 terephthalophenone units capped with hydrogen or isopropyl alcohol radicals or terminated by cyclization. II, the dimer, was capped by hydrogen atoms.
Reversible crosslinking in cellulose. III. Factors controlling the oxidation behavior of mercapto groups in cotton derivatives
Authors: Sakamoto Munenori , Takeda Junichi , Yamada Yoshio , Tonami Hiroaki 
Published: April 2003

AbstractThe oxidation behavior of mercaptocellulose prepared from tosylated cotton and of cellulose β‐mercaptoethylaminocarboxylate (RDTC), which was prepared by reduction of a cotton derivative made by the reaction with bis‐β‐isocyanatoethyl disulfide, was studied, and the factors controlling the oxidation behaviors of solid polymeric mercaptans were discussed. RDTC was converted quantitatively to the corresponding disulfide by oxidation under mild conditions. Repeated oxidation–reduction cycles were applied to RDTC to demonstrate complete reversibility of disulfide crosslinking. On the other hand, only a portion of the mercaptan in mercaptocellulose could form disulfide by oxidation. It is considered that the mobility of the mercapto groups necessary for the oxidation coupling is restricted because they are attached directly to rigid cellulose chains. The oxidation of RDTC with air in alkaline medium was studied kinetically. It was found that the oxidation of the mercaptan in paired placement in the cellulose matrix proceeded more than ten times faster than that of the randomly placed mercaptan.
Polymerization of complexed monomers. I. Alternating copolymers from cyclopentene and complexed polar monomers
Authors: Hecht Jeffrey K. 
Published: April 2003

AbstractAlternating equimolar copolymers of cyclopentene with acrylonitrile and methyl acrylate were prepared in the presence of ethylaluminum sesquichloride. Varying conditions of monomer ratio, temperature, light, and reaction time were studied. The structures of the polymers and mechanistic implications are discussed.