bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amide‐exchange reactions in mixtures of N‐alkyl amides and in polyamide melt blends
Authors: Miller I. K. 
Published: April 2003

AbstractThe amide‐exchange reactions which cause copolymer formation in polyamide melt blends were studied with mixtures of N‐ethylcaproamide and N‐hexylacetamide containing small concentrations of caproic acid and hexylamine as a model system for melt blends of aliphatic polyamides. Amide exchange was found to involve acidolysis and aminolysis reactions with no detectable contribution of direct reaction between amide groups. Kinetics data are consistent with formation of an anhydride intermediate in amide acidolysis. Rate constants over the range 200–275°C and activation energies for amide acidolysis and aminolysis reactions are given. Equations are given for calculating amide exchange rates in polyamide melt blends and for relating degree of amide exchange to block copolymer composition.
Preparation and properties of polyamides and polymides containing bibenzyl, stilbene, and tolan structures
Authors: Inoue Kazuto , Imai Yoshio 
Published: April 2003

AbstractPolyisophthalamides and polyterephthalamides were prepared by the solution polycondensation of the corresponding diacyl chlorides with 4,4′‐diaminobibenzyl, trans‐4,4′‐diaminostilbene, and 4,4′‐diaminotolan in N,N‐dimethylacetamide (DMAc). Polypyromellitimides were synthesized in two steps by the ring‐opening polyaddition of pyromellitic dianhydride with the aromatic diamines in DMAc, followed by thermal cyclodehydration. The amorphous polyisophthalamides were soluble in some amide solvents containing lithium chloride, while the polyterephthalamides having fair degree of crystallinity were insoluble in these solvents. The thermal stability of these aromatic polymers decreased in the order of the tolan‐containing polymers > the stilbene‐containing polymers > the bibenzyl‐containing polymers, both in air and under nitrogen.
ESR study on photodecomposition mechanism of oxidized poly(vinyl alcohol)
Authors: Yasunaga Toshio , Kubota Hitoshi , Ogiwara Yoshitaka 
Published: April 2003

AbstractPhotolysis behavior of oxidized poly(vinyl alcohol) (PVA) in which carbonyl groups were introduced by oxidation with sodium hypochlorite and periodic acid was investigated by using ESR spectrometry. Increased formation of PVA radicals was observed in the sample with low degree of oxidation, which showed an emphasized formation of triplet component radical. On the other hand, the formation of radicals tended to be depressed in the highly oxidized sample, and a singlet component was dominant in the ESR spectrum. By examining infrared and ultraviolet spectra of the oxidized sample, the sample was found to contain two structures, a saturated ketone group and an α,β‐unsaturated group; the latter structure was intensified with increasing degree of oxidation. Based on ESR studies of the photoirradiated acetone and mesityl oxide, the models of saturated and α,β‐unsaturated ketone structures in the oxidized PVA, respectively a photodecomposition mechanism of oxidized PVA was proposed.
Multiblock copolymers of styrene and isoprene. I. Synthesis and characterization
Authors: Corbin N. , Prud'Homme J. 
Published: April 2003

AbstractAn anionic polymerization procedure for preparing multiblock copolymers of styrene and isoprene is described. The process is based on the initial specific incorporation of isoprene when mixtures of styrene and isoprene are polymerized with butyllithium in hydrocarbon solution. As examples, linear (AB)3 block copolymers have been prepared by interrupting styrene polymerization by step additions of isoprene at times programmed according to the reactivity ratios and the rate constants for styrene and isoprene propagations. The products were characterized by means of osmometry, light scattering, gel‐permeation chromatography, and density‐gradient ultracentrifugation. The analyses showed that the multiblock copolymers are free from polymeric impurities and reasonably homogeneous in molecular weight and composition. The polystyrene segment lengths were analyzed by means of GPC after the oxidative degradation of the polyisoprene moieties in the copolymers. The results suggest that the polyisoprene blocks contain a nonnegligible amount of styrene but that this monomer is incorporated as very short segments. On the other hand the polystyrene blocks produced at the end of the copolymerizations appear to have narrow molecular weight distributions.
Chemical modification of polymers. VII. Condensation of polymeric aldehydes with the anion of an isoquinoline reissert compound
Authors: Gibson Harry W. , Bailey F. C. 
Published: April 2003

AbstractThe anion of the isoquinoline Reissert compound, 2‐benzoyl‐1,2‐dihydroisoquinaldonitrile, reacts with polymeric aldehydes in essentially complete conversion, leading to polymeric esters containing isoquinoline moieties. These can be completely hydrolyzed to the corresponding alcohols. The reactivity of the Reissert anion toward polymeric halides and aldehydes is rationalized on the basis of its moderate hardness.
Oxysilane polymers from silanediol–bisdimethylaminosilane polycondensations: Synthesis and properties
Authors: Pittman Charles U. , Patterson William J. , McManus Samuel P. 
Published: April 2003

AbstractThe solution polycondensation of 1,4‐bis(hydroxydimethylsilyl)benzene with six bis(dimethylaminosilanes) was carried out by the aminosilane deficient method to give a series of high polymers. The bis(dimethylaminosilanes) were bis(dimethylamino)dimethylsilane, bis(dimethylamino)methylphenylsilane, bis(dimethylamino)diphenylsilane, 1,4‐bis(dimethylaminodimethylsilyl)benzene, 1,3‐bis(dimethylamino)‐1,1,3,3‐tetramethyldisiloxane, and 1,5‐bis(dimethylamino‐1,1,3,3,5,5‐hexamethyltrisiloxane). The condensation of dihydroxymethylphenylsilane with bis‐(dimethylamino)methylphenylsilane to give polymethylphenylsiloxane was also performed. A detailed description of the monomer syntheses and polymerization reactions is provided, since this paper represents the first detailed and systematic description of this polycondensation as an alternative to disilanol or disilanol‐dichlorosilane condensation routes. The thermal properties (i.e., Tg, TGA, DSC) of poly(p‐phenylenetetramethylsiloxane) are compared to those of poly[1,4‐bis(oxydimethylsilyl)benzenel] (where a Si(Me)2O group has been inserted between the silylphenylene units) as well as others in this series, polydimethylsiloxane, and polymethylphenylsiloxane. Similarly, these properties are compared with those of related polymers which include in‐chain ferrocene units. Introduction of Si(Me)2O units into poly(tetramethyl‐p‐silylphenylenesiloxane) systematically decreases Tg and thermal stability. Replacing SiCH3 with SiC6H5 groups increases Tg and thermal stability. Replacing in‐chain C6H4 with ferrocene increases Tg and slightly decreases thermal stability. The values of K and A in the Mark‐Houwink equation were determined for several polymers.
Theory of stabilizing thermally stable polymers
Authors: Gladyshev G. P. 
Published: April 2003

AbstractIt has been discovered that chemical compounds generated in some polymeric samples or articles and possessing high activity in the reactions with oxygen and free radicals as well as yielding inert products in the above reactions may stabilize the polymeric materials by inhibiting oxidative (and even thermal) degradation. The phenomenon described has both theoretical and experimental evidence.
Polymerization of N‐vinylcarbazole. II. Kinetic studies on polymerizations involving azoisobutyronitrile and benzoyl peroxide
Authors: Bevington J. C. , Dyball C. J. 
Published: April 2003

AbstractThe polymerization of N‐vinylcarbazole at 60°C in benzene has been initiated with azoisobutyronitrile, benzoyl peroxide, and their mixtures. The kinetics indicate that the azonitrile and the peroxide promote polymerizations of fundamentally different types. The resulting polymers have been examined by gel‐permeation chromatography. The polymer produced with benzoyl peroxide contains a small amount of a high molecular weight fraction which, from the point of view of end groups, resembles the polymer made by use of the azonitrile. It is concluded that benzoyl peroxide in this system gives rise to two types of polymerization which occur simultaneously.
Monomer‐isomerization polymerization. XVI. Monomer‐isomerization polymerization of methylpentenes with Ziegler‐Natta catalyst
Authors: Endo Kiyoshi , Otsu Takayuki 
Published: April 2003

AbstractThe polymerizations of 4‐methyl‐1‐pentene(4M1P), 4‐methyl‐2‐pentene (4M2P), 2‐methyl‐2‐pentene (2M2P), and 2‐methyl‐1‐pentene (2M1P) with Ziegler‐Natta catalyst have been investigated. Both 4M1P and 4M2P were found to polymerize with TiCl3–(C2H5)Al catalyst to give high molecular weight poly(4M1P), while 2M2P and 2M1P did not give polymers with 4M1P units. However, when the polymerizations of 2M1P and 2M2P were carried out with ternary catalyst systems, TiCl3–(C2H5)AlCl–(PPh3)2PdCl2 and TiCl3–(C2H5)AlCl–Ni(SCN)2 polymers with 4M1P units were obtained in low yield. It was concluded that these four methylpentenes could polymerize with the monomer‐isomerization polymerization mechanism to poly(4M1P). The results of the observed isomer distribution of methylpentenes recovered, and the rate of polymerization of four methylpentenes suggest that the isomerization from 2M1P to 4M1P with the above ternary catalyst systems might proceed via a direct one‐step isomerization mechanism.
Photochemistry of ketone polymers. XII. Studies of ring‐substituted phenyl isopropenyl ketones and their styrene copolymers
Authors: Sugita K. , Kilp T. , Guillet J. E. 
Published: April 2003

AbstractThe synthesis of a number of ring‐substituted phenyl isopropenyl ketones and their polymerization with styrene is reported. The ultraviolet absorption spectra of the polymers are analogous to those of ring‐substituted acetophenones and valerophenones. The quantum yields of the Norrish type II photoreaction were estimated in 1,2‐dichloroethane solution at 364 nm by automatic viscometry. These quantum yields are comparable to those of substituted butyrophenones and valerophenones, in that relatively high quantum yields were obtained for the unsubstituted and p‐chloro‐substituted compounds with low yields for p‐amino and p‐hydroxy compounds. The p‐nitro‐substituted compound gives no type II reaction, presumably because the excitation becomes localized on the nitro groups which photolyzes by a mechanism which does not involve chain scission. The implications of these studies on possible applications to photoimaging are discussed.
Effect of pH on the reactivity ratios in aqueous solution copolymerization of acrylic acid and N‐vinylpyrrolidone
Authors: Ponratnam S. , Kapur S. L. 
Published: April 2003

AbstractAcrylic acid (AA) and N‐vinylpyrrolidone (NVP) were copolymerized in aqueous solution at 30°C in the pH range 4–9 and the monomer reactivity ratios (r1 for AA and r2 for NVP) were determined as a function of pH from the high conversion data by using both the differential (YBR) and the integrated copolymerization equations. The value of r1 decreased from 5.2 at pH 4 to a minimum of 1.3 at pH 5 and then increased to 8.1, 6.6, and 7.2 at pH 7, 8, and 9, respectively. Addition of 1M NaCl at pH 6.5 restored the r1 nearly to that at pH 4, the predominantly un‐ionized acid. The r2 values for NVP were nearly zero at all pH values except at pH 5. The variation of the reactivity ratios with pH was examined in terms of the electrostatic interactions between the ionized monomer molecules, the rate of homopolymerization of acrylic acid, and the cation binding to the poly(acrylic acid) molecules. The r2 values for NVP compared favorably with the literature values reported in bulk and organic solvent systems, although r1 values are much higher.
Polymerization of coordinated monomers. XII. Alternating copolymerization of γ‐crotonolactone with styrene with the use of stannic chloride
Authors: Komiyama Makoto , Hirai Hidefumi 
Published: April 2003

Abstractγ‐Crotonolactone and styrene copolymerize alternately in the presence of stannic chloride at ‐10°C under photoirradiation. The intrinsic viscosity of the resulting copolymer is in the range of 0.6–0.8 dl/g at 30°C in chloroform. The equilibrium constants for the complex formation between stannic chloride and γ‐crotonolactone were determined in 1,2‐dichloroethane‐toluene solution at 0 and −20°C by use of absorption band at 350 nm. Continuous variation plots based on the 1H‐chemical shift show a 1:1 interaction between styrene and the γ‐crotonolactone coordinated to stannic chloride. The equilibrium constants for the ternary molecular complex formation between the coordinated γ‐crotonolactone and styrene were determined in 1,2‐dichloroethane in the temperature range from −20 to 0°C. The equilibrium constants, derived independently from the measurements of the nonequivalent protons in γ‐crotonolactone, are equal to each other within the experimental error. The mechanism of the alternating copolymerization of γ‐crotonolactone and styrene in the presence of stannic chloride is discussed in terms of the homopolymerization of the ternary molecular complex.
Oligomeric polyaromatic ether‐ketone‐sulfones with acetylenic end groups. IX.
Authors: Kellman Raymond , Marvel C. S. 
Published: April 2003

AbstractTwo oligomeric polyaryl ether‐ketone‐sulfones with acetylenic end groups have been prepared. These materials which are low melting and readily soluble in organic solvents on heating undergo reactions which are presumably trimerizations of the terminal acetylenic groups to give cured polymers which do not soften until about 200°C and which are stable in circulating air at 300°C with less than 10% weight loss in 10 days.
Solid‐state polymerization of N‐carboxy‐L‐leucine anhydride crystals in n‐hexane
Authors: Oya Masanao , Takahashi Tomoko , Katakai Ryoichi 
Published: April 2003

Abstract4‐Isobutyloxazolidinedione, L‐leucine N‐carboxy anhydride, was polymerized to produce high molecular weight polymer with triethylamine in n‐hexane which is not a solvent for the N‐carboxy anhydride and poly‐L‐leucine. It was found that as the crystal size became smaller, the total surface area was increased, the initial rate of polymerization was increased, and inherent viscosity of the formed polymer was decreased.
1:1 alternating copolymer of acrylonitrile and vinyl acetate
Authors: Chen Catherine S. Hsia 
Published: April 2003

AbstractCopolymerization of the acrylonitrile‐zinc chloride complex with excess vinyl acetate has been investigated. Alternating 1:1 copolymers of acrylonitrile and vinyl acetate of high molecular weights have been successfully prepared. The alternating structure has been ascertained by means of high‐resolution nuclear magnetic resonance spectroscopy. The copolymer is amorphous (Tg = 85°C) and has shown thermal and oxidative stability better than those of polyacrylonitrile. The copolymer is soluble in acetone as well as in more powerful solvents such as dimethylformamide, dimethyl sulfoxide, nitromethane, and N‐methylpyrrolidone. The copolymer has been processed into films and fibers from its acetone solutions. Films show tensile properties similar to those of cellulose acetate under ambient conditions; they suffer drastic loss in tensile properties at above 50°C and retain their good tensile properties at subzero temperatures (determined as low as −40°C). Fibers show tensile properties comparable to those of modacrylic fibers under ambient conditions but suffer marked loss in stiffness at 40°C in water and 60°C in air. The fibers also retain their good properties at subzero temperatures (measured down to −60°C).
Molecular weight determination of vinylidene chloride copolymers by gel‐permeation chromatography and viscometry
Authors: Revillon A. , Dumont B. , Guyot A. 
Published: April 2003

AbstractThis is the first report on the characterization of several pairs of random copolymers of vinylidene chloride by gel‐permeation chromatography in conjunction with viscometry. Such copolymers have not previously Received much attention, so we first determined the individual viscosity–molecular weight relationship. The K–a values were compared with known values for the parent homopolymers. We then derived calibration curves (different for each composition) and the calculation of the average molecular weight. These results are compared to those obtained by direct methods, without fractionation, and to kinetic observations. This method avoids misinterpretation of viscosity data and elution volume. Chromatograms may indicate heterogeneity of the compounds as related to polymerization conditions.
Polyimide structure–property relationships. II. Polymers from isomeric diamines
Authors: Bell Vernon L. , Stump Billy L. , Gager Helen 
Published: April 2003

AbstractAn extensive study of the effects of stereoisomeric variations in aromatic polyimide structures on polyimide properties was conducted. The structural variations were incorporated into the polyimides through the use of two complete series of isomeric aromatic diamine monomers, the diaminodiphenylmethanes and the diaminobenzophenones, as well as several pairs of diamine isomers. The ability of the diamines to polymerize was related to the basicities, and thus reactivities, of the amino groups. Diamines with an amino group located ortho to the group connecting the two aromatic rings were successfully polymerized with dianhydrides for the first time to high molecular weight poly(amic acids). The stereoisomeric polyimides were characterized by determining the glass transition temperatures Tg, mechanical properties, and thermooxidative stabilities of thin films of the polymers. The polymers prepared from p‐diamines were shown to have the highest softening points and thus, the most rigid molecular structures. Those synthesized from m‐diamines had the lowest Tg values, inferring the most flexible molecular backbone. With limited exceptions, the use of diamines with ortho‐oriented amine groups failed to improve the flexibility of the polyimides since their Tg values were usually as high as those of polymers made from p‐diamines. Only slight differences in mechanical properties of the isomeric polyimide films were attributable to the variations in isomeric structure, except for those properties dependent upon Tg changes, such as elevated temperature mechanical properties. A study of the thermooxidative stability of the polyimides showed little difference between the polymers prepared from the diaminobenzophenones, but marked differences were observed between the individual members of the diaminodiphenylmethane‐derived polyimides.
Characterization of novolac resins based on p‐tert‐butylphenol by PMR spectroscopy
Authors: Nowlin T. E. , Boyd W. H. 
Published: April 2003

AbstractThe direct silylation of tert‐butylphenol formaldehyde resins with N,O‐bis(trimethylsily)acetamide (BSA) has allowed a more complete analysis of these resins to be made with proton magnetic resonance (PMR) spectrometry. A quantitative determination of mixtures of the monomer, dimer, trimer, and tetramer may be carried out at 100 MHz.
EPR study of the photoinitiated polymerization of butadiene and of an isobutylene–butadiene mixture in the presence of VCl4
Authors: Pilař J. , Toman L. , Marek M. 
Published: April 2003

AbstractThe EPR spectra of butadiene and of a mixture of butadiene and isobutylene in the presence of VCl4 in the dark and with irradiation have been studied. The effect of light on butadiene leads to the formation of the radical‐cation of butadiene, similarly to isobutylene. In the mixture of both monomers, radical cations of isobutylene and butadiene are formed under the effect of light. Even if isobutylene is present in excess in the mixture compared to butadiene, the formation of the radical‐cation of butadiene still prevails. In presence of oxygen, with both butadiene and the isobutylene–butadiene mixture, peroxy radicals were detected. Cyclic polybutadiene was the main product of the photochemically initiated polymerization of butadiene.
Higher aliphatic polyaldehydes. II. Polymer structure and polymer stability of poly(n‐heptaldehyde)
Authors: Negulescu I. , Vogl O. 
Published: April 2003

AbstractPoly(n‐heptaldehyde) has been prepared by anionic and cationic polymerization at −60°C in methyl cyclohexane. The anionic polymer is more crystalline and of a higher degree of isotactic structure than the somewhat rubbery but still crystalline cationic polymer. The polymers have been acetate‐endcapped to improve their thermal stability. Cationic polymer, when endcapped and purified, begins to degrade above room temperature; even crystalline anionic polymer degrades at a reasonable rate at 100°C. The crystallinity of poly(n‐heptaldehyde) is caused by crystallization of the acetalic main chain as well as the side chain. Two regions of melting have been recognized by DSC analysis and by microscopic observations. The low melting region between 80 and 100°C has been identified as the melting of the paraffinic side chains of poly(n‐heptaldehyde). It consists of three clearly definable endotherms at 78, 87, and 101°C.
Voltammetric behavior of poly(vinylferrocene)
Authors: Smith Thomas W. , Kuder James E. , Wychick Darlene 
Published: April 2003

AbstractA voltammetric analysis of the electron‐transfer process in poly(vinylferrocene) (PVF) has been carried out; the results indicate that the electrochemical behavior of ferrocene and PVF are quite similar. The field effects in the macromolecular environment do, however, appear to influence the microscopic potential for oxidation of adjacent ferrocene residues in PVF. Analysis of the slopes of plots of limiting current versus the square root of the rotation speed indicate that only “isolated” ferrocene residues in the polymers are oxidized under the conditions of the rotating‐disk electrode experiment.Diffusion coefficients were determined experimentally for ferrocene and its macromolecular analogs were quite close to those simply calculated from the Stokes‐Einstein relationship. Further, it was demonstrated that the molecular weight, which is inversely proportional to the diffusion coefficient, could be determined by voltammetric techniques.
Determination of branching in polyethylene and poly(vinyl chloride) using pyrolysis gas chromatography
Authors: Ahlstrom David H. , Liebman Shirley A. , Abbås Kent B. 
Published: April 2003

AbstractA series of polyethylenes (PE), reduced poly(vinyl chlorides), and precursor poly(vinyl chloride) (PVC) systems were studied by pyrolysis–gas chromatography (PGC) and by pyrolysis–hydrogenation–gas chromatography (PHGC). The branch content of these polymers has been interpreted on the basis of previously established literature information. Low‐density PE (LDPE) was found to contain a significant number of ethyl branches. The pyrolysis results on an LAH‐reduced PVC series gave significant insight on PVC microstructure. It was determined that the short‐chain branches in PVC are mainly one carbon long. Some ethyl side chains and virtually no butyl branches were found in this experimental PVC series. The effect of chain branching on the pyrolysis of PVC is to increase fragmentation. The benzene/toluene ratio, along with relative amounts of benzene and naphthalene formed, may be used to indicate the relative degree of branching in this system. The application of PGC and PHGC have thus been shown to successfully extend analytical work on PE and PVC and to provide microstructural information.