bluuebunny/crossref_metadata_2025_split huggingface dataset:
NMR study of vinyl chloride–vinylidene chloride copolymer
Authors: McClanahan J. L. , Previtera S. A. 
Published: April 2003

AbstractA study of the proton magnetic resonance spectra of poly(vinyl chloride) (PVC), poly(vinylidene chloride) (PVDC), and vinyl chloride–vinylidene chloride (VC–VDC) copolymer has resulted in a clearer understanding of the copolymer NMR spectra. Comparison of the homopolymer spectra with the copolymer spectra, including information obtained from decoupling experiments, indicated that the chain structure of the eight copolymers studied were of two different types. The simplest type copolymer chain contained head‐to‐tail VDC sequences, head‐to‐head or tail‐to‐tail VDC sequences, and VC‐VDC sequences. The second type copolymer contained all of the sequences of type I copolymers and, in addition, contained VC sequences. The average length of these VC sequences was less than four VC units. The composition of seven of the copolymers was determined by chlorine analysis and by an NMR method of analysis which was based on the above conclusions. The agreement between the results of the two methods of analysis was quite good.
Thermochemistry of polymerization part III. Thermochemical aspects of propagation of polymerization
Authors: Sawada Hideo 
Published: April 2003

AbstractA statistical thermodynamic method of treating propagation of polymerization is developed. The effect of temperature on the sequence distribution of syndiotactic and isotactic units in free‐radical polymerization is discussed. This theory applies to the problem of probabilities of various possible modes of addition, namely head‐to‐head and head‐to‐tail addition, 1–2 and 1–4 addition, and formation of cis and trans configurations.
Contribution à l'étude de l'ionisation des polyelectrolytes à l'interface air–eau
Authors: Jaffe J. , Ruysschaert J.‐M. 
Published: April 2003

AbstractMonolayers of poly‐2‐vinylpyridine (2‐PVP), of poly(methacrylic acid) (PMA), as well as of a polyampholyte containing definite proportions of 2‐vinylpyridine and acrylic acid were investigated at the air–water interface. We studied particularly the ionization of the film. The variation of surface pressure with respect to the nature of the ionic subsolution was analyzed. At constant degree of ionization, two factors determine the surface pressure: the valence and the dimension of the counterion. The polyampholyte may be considered alternatively as a polycation or a polyanion depending on the pH value of the support. The small concentration of dipolar ions permits the presence in the same macromolecule of the properties of the poly‐2‐vinylpyridine and of the poly(methacrylic acid). Qualitatively, the influence of the counterions is reproduced for the three polyelectrolytes. With monovalent ions, a quantitative approach is possible. The surface pressure is analyzed in terms of current theories of the ionic double layer. The application of the Gouy‐Chapman model gives satisfactory results at different polymer and ionic concentrations. The theory has been extended with success to completely and incompletely ionized monolayers. However, there is evidence that the Gouy‐Chapman theory is obeyed only at high areas. For denser films, the discrepancy between the calculated and experimental pressure is often quite large. The inclusion of a “fluctuation potential” contribution to the surface pressure permits a good agreement between the theory and the experiments.
Melting point and heat of fusion of poly(vinyl alcohol)
Authors: Tubbs Robert K. 
Published: April 2003

AbstractDifferential thermal analysis was used to study the effect of a diluent, glycerol, and copolymer units, acetate groups, on the melting point of poly(vinyl alcohol) (PVA). The melting point of PVA was found to be 228°C. and the heat of fusion by the diluent and copolymer methods was 1.64 and 0.56 kcal./mole, respectively, based on vinyl alcohol units. Flory's theory was used as a basis for analysis. The results are compared with literature values for the heat and entropy of fusion of polyethylene, and the differences briefly discussed.
Polydisperse polymers with random trifunctional branching. I. Evaluation of the extent of branching
Authors: Shultz A. R. 
Published: April 2003

AbstractThe relation of intrinsic viscosity of weight‐average molecular weight and branch density is derived for polydisperse polymers having randomly distributed trifunctional branch points. The results are obtained by specializing and approximating a general molecular distribution function derived by Stockmayer and incorporating this function into the polymer solution viscosity treatment of Zimm and Kilb. Numerical values of the molecular size distribution function and of the intrinsic viscosity functions are tabulated for selected branch densities.
Fractionation of cellulose trinitrates by gel permeation chromatography
Authors: Segal Leon 
Published: April 2003

AbstractSamples of the four polymorphic forms of cellulose (I, II, III, and IV) have been nitrated and examined by means of gel permeation chromatography (GPC). Shifts in the differential and integral distribution curves indicate that the processes for lattice conversion affect the molecular weight distribution of the cellulose molecules in the samples. Weight‐average and number‐average degrees of polymerization for the four samples exhibit trends parallel to those observed in the average degrees of polymerization of the initial celluloses measured viscometrically where the celluloses were dissolved in cupriethylene diamine and in cadmium ethylene diamine hydroxide solutions. The weight‐ and number‐average values, however, are markedly greater than the viscosity values. The order of magnitude of the GPC data, however, was similar to average degrees of polymerization of cellulose reported in the literature which were obtained by other methods.
Co60 γ‐radiation‐induced copolymerization of ethylene and carbon monoxide
Authors: Colombo P. , Kukacka L. E. , Fontana J. , Chapman R. N. , Steinberg M. 
Published: April 2003

AbstractThe γ‐radiation‐induced free‐radical copolymerization of ethylene and CO has been investigated over a wide range of pressure, initial gas composition, radiation intensity, and temperature. At 20°C., concentrations of CO up to 1% retard the polymerization of ethylene. Above this concentration the rate reaches a maximum between 27.5 and 39.2% CO and then decreases. The copolymer composition increases only from 40 to 50% CO when the gas mixture is varied from 5 to 90% CO. A relatively constant reactivity ratio is obtained at 20°C., indicating that CO adds 23.6 times as fast as an ethylene monomer to an ethylene free‐radical chain end. For a 50% CO gas mixture, the above value of 23.6 and the copolymerization rate decrease with increasing temperature to 200°C. The kinetic data indicate a temperature‐dependent depropagation reaction. Infrared examination of copolymers indicates a polyketone structure containing CH2CH2 and CO units. The crystalline melting point increases rapidly from 111 to 242°C., as the CO concentration in the copolymer increases from 27 to 50%. Molecular weight of copolymer formed at 20°C. increased with increasing CO, indicating M̄n values >20,000. Increasing reaction temperature results in decreasing molecular weight. Onset of decomposition for a 50% CO copolymer was measured at ≈250°C.
Radiation‐induced graft polymerization of styrene to poly(vinyl chloride)
Authors: Takamatsu Toshiaki , Shinohara Kenichi 
Published: April 2003

AbstractThe radiation‐induced graft polymerization of styrene to poly(vinyl chloride) (PVC) was investigated. Relations between the rate of grafting and the dose rate when the polymer is irradiated in liquid monomer or in monomer vapor, and between the rate of grafting and monomer concentration absorbed in the polymer have been investigated. The rate of grafting in monomer vapor was found to be far larger than that in liquid monomer. A high rate of grafting in monomer vapor was thought to result from a lower concentration of monomer in PVC during irradiation. An experiment carried out on PVC containing the monomer at various concentrations showed that the rate is largest at a monomer concentration of about 3.5 mole/l. and is smaller for higher and lower concentrations. On the assumption that the theory of homogeneous homopolymerization can be applied to this grafting reaction, the value of kp2/kt has been obtained, where kp and kt are propagation constant and termination constant, respectively. The value of kt greatly increases when the monomer concentration exceeds 3.5 mole/l. This increase of kt can be accounted for if it is assumed that the monomer absorbed in the polymer works as a plasticizer and increases the molecular motion of the polymer. A measurement of the elastic modulus of PVC containing the monomer at various concentrations showed that this is, in fact, the case.
NMR study of model compounds of vinyl polymers
Authors: Fujiwara Yuzuru , Fujiwara Shizuo , Fujii Kiyoshi 
Published: April 2003

AbstractComplicated NMR spectra of vinyl polymers provide conformational and configurational knowledge of the polymers in solution. Explicit expressions for the spectral frequencies and intensities are obtained by the analysis of vinyl polymers and their model compounds as weakly coupled systems. The classified spectra expected for common vinyl polymers are presented by using the results of the analysis. The analysis is applied to model compounds of poly(vinyl alcohol) and poly(vinyl acetate) in solution. The results show that conformations of poly(vinyl alcohol) are determined by the intramolecular hydrogen bonding so that the syndiotactic isomer forms a helical structure, the isotactic one a planar zigzag structure. The poly(vinyl acetate) produces a helical structure for isotactic isomer by the repulsion of side chains and a planar zigzag for the syndiotactic isomer.
Polymerization with organoboron compounds
Authors: Arimoto F. S. 
Published: April 2003

AbstractIn the presence of organoboron compounds, free‐radical polymerization of vinyl monomers can proceed in spite of the presence of excess of typical radical inhibitors. The concept of free radical–organoboron complex formation is introduced to explain the unique role of organoboron compounds in such a polymerization system.
Polymerization of five‐, six‐, and seven‐membered ring lactams by using metallic potassium or metallic aluminum alkylate as catalyst and certain N‐acyl lactams or diphenyl ketene as initiator
Authors: Tani Hisaya , Konomi Tuyoshi 
Published: April 2003

AbstractPolymerization of five‐, six‐, and seven‐membered lactams by metallic potassium or MAlEt4 (where M is Li, Na, or K) as a catalyst and N‐acyl lactam or diphenylketene as an initiator was carried out at temperatures below 80°C. By using MAlEt4 instead of a metallic potassium catalyst in the polymerization of α‐piperidone the propagation was continued until the reduced viscosity of polymer reached a value of 0.9. The polymer obtained has a film‐forming ability. The experimental results obtained in the gasometry suggest that MAlEt4 reacts with lactam to form such a complex of the type
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(where M is Li, Na, or K and X is an ethyl or 2‐oxo‐alkylene‐imine group). The resulting complexes are considered to increase the solubility of catalyst and also to protect the polymer endgroups from side reactions by stabilizing the alkali metal as the complex. In addition, the mode of action of diphenylketene as an initiator was revealed by the facts that the corresponding N‐diphenylacetyl lactam was obtained from the reaction of diphenyl ketene with lactam and N‐diphenylacetyl lactam itself was useful for the polymerization of α‐piperidone.
The role of diffusion in propylene polymerization
Authors: Begley J. W. 
Published: April 2003

AbstractThe role of monomer diffusion in the polymerization of propylene by organometallic catalysis was examined by use of mathematical models which couple the rate of diffusion through the polymer film surrounding the catalyst with the rate of surface reaction. An approximate form of a second‐order, integrated rate equation was used to describe the disappearance of active sites on the surface. For the most conservative model conceivable, it was estimated that the particle size would have to be 10–100 times the size for the catalysts presently in use before diffusion time would be significant. The size of the catalysts was determined by photomicrographs and nitrogen adsorption surface areas. The surface areas for three different catalysts were 7, 20–21 and 35 m.2/g., respectively. The kinetic model without the diffusion term was used satisfactorily to correlate productivity data. The characteristic decline in reaction rate was examined in terms of the decay of active sites on the surface of the catalyst. The rate of decay was determined to be second order with respect to the site concentration. The kinetic model indicates that the total polymerization time for a specified productivity is the sum of the monomer diffusion time and the surface reaction time. The model derived by use of an approximate second‐order decay function is unique because of the additivity of diffusion and reaction times, which is not the case when the second‐order function is used rigorously.
Pyrolysis of vinyl and vinylidene fluoride polymers: Influence of prior γ‐irradiation
Authors: Wall L. A. , Straus S. , Florin R. E. 
Published: April 2003

AbstractQuantitative comparisons were made between the rates of thermal volatilization of several fluoropolymers before and after exposure to γ‐radiation. The effects of γ‐irradiation on poly(vinyl fluoride) and poly(vinylidene fluoride) were also investigated by swelling and sol‐gel ratios. With both polymers as well as with polytrifluoroethylene, crosslinks occur predominantly, though there is an appreciable number of scissions. The rates of volatilization and char formation were enhanced by γ‐radiation, whereas the previously studied polytrifluoroethylene did not produce more char upon irradiation, although radiation did accelerate its volatilization. It is believed that in polytrifluoroethylene the enhanced rates of volatilization occur by a different mechanism than in the case of the vinyl and vinylidene fluoride polymers.
γ‐Radiation‐induced ionic polymerization of pure liquid styrene
Authors: Potter R. C. , Johnson C. L. , Metz D. J. , Bretton R. H. 
Published: April 2003

AbstractPure liquid styrene, carefully purified and exhaustively dried, exhibits kinetic behavior under γ‐irradiation that can best be described in terms of an ionic mechanism. This is based on the observed linear dependence of the rate of polymerization on the dose rate, the independence of molecular weight on the same parameter, and comparison with the thermal and ultraviolet initiated polymerization of monomer prepared under the same stringent conditions. The highest rate of conversion to polymer is 400%/hr. at a dose rate of 106 rads/hr., corresponding to a G(‐monomer) ≈ 40,000.
Kinetics of heterogeneous cellulose reactions. I. Cyanoethylation of cotton cellulose
Authors: Chatterjee Pronoy K. , Conrad Carl M. 
Published: April 2003

AbstractSakurada's equation and fundamental kinetic laws were applied to the heterogeneous cyanoethylation of cellulose, performed by reacting fiber with liquid acrylonitrile, with sodium hydroxide as the catalyst. The data fit Sakurada's equation better at higher temperatures; deviation occurs at the initial stage, and the rate of reaction falls abruptly at a later stage. The degree of substitution at which the abrupt rate change occurred decreased as the temperature increased from 31 to 60°C. and also as the crystallinity of the fiber decreased. Diluting the reagent with different solvents decreased the rate of reaction and changed its transition points, but did not change the essential nature of the reaction, each segment of which fits Sakurada's equation very well. A uniform distribution of the catalyst (sodium hydroxide) throughout the fiber was attempted, and then the reaction was studied at 50°C. Diffractograms of the samples provided further evidence that the position of the rate change is associated with the change of cellulose (I) crystalline structure. Approximate energy of activation has been calculated, from the specific rate constants, between 31 and 40°C. as 10.6 kcal. and between 45 and 50°C. as 16.7 kcal. At other temperatures the determination was handicapped, due to temperature dependence of the order of reaction. An empirical relation between the constants of Sakurada's equation and the reaction temperature has been sought and correlated with the Arrhenius equation. Energies of activation, determined from this relationship, have been found to be very close to the above values. The change of order of reaction with temperature suggests that the reaction is affected by diffusion and the mechanism is interpreted as a diffusion‐controlled reaction where hydrogen bonds play a significant role in diffusion.
Increased rates of initiation of polymerization by 4‐4′‐dicyano‐4‐4′‐azopentanoic acid in the presence of ferric salts
Authors: Cavell E. A. S. , Gilson I. T. 
Published: April 2003

AbstractThe initiation of the polymerization of acrylamide by 4‐4′‐dicyano‐4‐4′‐azopentanoic acid in aqueous solution has been studied kinetically at 25°C. Ferric chloride and ferric sulfate were used to terminate polymerization so that rates of initiation could be calculated from the rates of production of ferrous iron. Velocity coefficients at 25°C. for the initiation reaction were found to be (25.7 ± 2.8) × 10−7 sec.−1 for the ferric chloride terminated reaction and (73.6 ± 0.6) × 10−7 sec.−1 for the ferric sulfate‐terminated polymerization. The value reported for the initiation reaction when acrylamide is polymerized in the absence of metal salts is 1.29 × 10−7 sec.−1. Velocity coefficients for the termination reaction have been calculated from the overall rates of polymerization obtained with ferric salts present. In the case of the ferric chloride‐terminated reaction, it has been shown that the rate of polymerization is reduced by increasing the total concentration of chloride ions. Termination velocity coefficients at 25°C. for the inner sphere complexes FeCl2+·5H2O and FeSO4+·4H2O have been calculated to be 18.9 × 104 and 7.98 × 104 l./mole‐sec., respectively. The dependence on the concentration of ferric chloride of the molecular weights of the polymers produced has also been considered.
Polyquinoxalines. III
Authors: Stille J. K. , Arnold F. E. 
Published: April 2003

AbstractSix thermally stable polyquinoxalines have been prepared by the reactions of combinations of three tetraamines, 3,3′,4,4′‐tetraaminodiphenyl sulfone (II), and 3,3′,4,4′‐tetraaminodiphenyl ether (V), with two bisglyoxals, 4,4′‐diglyoxalyldiphenyl sulfide dihydrate (III) and 4,4′‐diglyoxalyldiphenyl sulfone dihydrate (IV). The polymers were prepared from polymerization in two stages. The first stage, a solution polymerization, produces an initially low or moderate molecular weight material, which is advanced to a high molecular weight (ηinh > 1.0) by heating at 375°C. under reduced pressure. All the polyquinoxalines have excellent thermal stability both in nitrogen and in air and improved solubility.
Inorganic coordination polymers. VII. Zinc(II) dimethyl‐, methylphenyl‐, and diphenylphosphinates
Authors: Rose Selwyn H. , Block B. P. 
Published: April 2003

AbstractZinc dimethyl‐, methylphenyl‐, and diphenylphosphinate have been prepared by the reaction of Zn(C2H3O2)2·2H2O with the appropriate acid or salt and found to exist in amorphous and crystalline forms. Zinc methylphenylphosphinate, the most tractable, exhibits many of the physical attributes of polymeric materials, both in solution and bulk form, supporting our earlier suggestion that these compounds are double‐bridged coordination polymers. Thermogravimetric analysis indicates initial decomposition temperatures of 440, 425, and 490°C., respectively, for the three polymers, but long‐term studies show initiation of decomposition at somewhat lower temperatures.
Promotion of base‐catalyzed siloxane rearrangements by dimethyl sulfoxide
Authors: Cooper Glenn D. , Elliott John R. 
Published: April 2003

AbstractThe effect of small amounts (0.01%–1%) of dimethyl sulfoxide on base‐catalyzed polymerization and equilibration of methylsiloxanes has been examined. The addition of 0.5% of the sulfoxide increases the rate of potassium hydroxide‐catalyzed polymerization of octamethylcyclotetrasiloxane by factors of 100–1000 and amounts as low as 0.01% have a large effect when low (12 ppm) catalyst concentrations are used. The rate of basecatalyzed equilibration of hexamethyl disiloxane with octamethylcyclotetrasiloxane is similarly enhanced by dimethyl sulfoxide. The equilibration occurs rapidly at 80°C. with 0.01% of potassium hydroxide and 1% of dimethyl sulfoxide, but does not proceed at a measurable rate with potassium hydroxide alone. The combination of 0.01% potassium hydroxide and 1% dimethyl sulfoxide is more effective than 0.1% of tetramethylammonium hydroxide. The large accelerating effect of the sulfoxide is believed to be due to solvation of the cation, which promotes ionization of the metal silanolate, increasing the concentration of silanolate anions.
γ‐Irradiation of poly(ethylene terephthalate). I. Yields of gas and carboxyl groups
Authors: Burow S. D. , Turner D. T. , Pezdirtz George F. , Sands George D. 
Published: April 2003

AbstractPoly(ethylene terephthalate) was exposed in vacuo γ‐radiation from a Co60 source at a dose rate of 0.02 Mrad/min., and an ambient temperature of 47°C. Gaseous products were analyzed in a mass spectrometer and carboxyl groups estimated by titration with NaOH and by infrared analysis. Initial G values were COOH = 0.77, CO2 = 0.17, CO = 0.11, H2 = 0.015, and CH4 = 0.003. All these values decreased markedly with increasing dose except G(CO)2, which, roughly, was maintained up to 5000 Mrad. It was considered whether the dependence on dose of the yields of the major reaction products could be accounted for by the following set of first‐order reactions:
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It was found that the rate of formation of COOH groups at low doses was much too high to fit this simple reaction scheme. However, a better fit was obtained over a range of higher doses (ca. 100–5000 Mrad). A final conclusion could not be reached concerning the validity of the above reaction scheme.
Structure–property relationships of poly(vinyl alcohol). II. The influence of molecular regularity on the crystallization–dissolution temperature relationships of poly(vinyl alcohol)
Authors: Harris H. E. , Kenney J. F. , Willcockson G. W. , Chiang R. , Friedlander H. N. 
Published: April 2003

AbstractDissolution temperatures Ts have been determined for poly(vinyl alcohol) (PVA) samples of varying tacticity as a function of crystallization temperatures Tc. From the values of Ts and Tc, one can obtain values of (Tm)∞, the dissolution temperature of crystals of infinite stepheight. (Tm)∞ is a characteristic property of a given sample. This method of characterization is very sensitive and reliable for detecting differences in molecular regularity among PVA samples. The variation of (Tm)∞ with stereoregularity is attributed in part to differences in hydrogen‐bonding characteristics. Determinations of the crystallinities of solution‐crystallized PVA have shown that stereoregularity in PVA does not result in higher crystallizability.