bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure effects and related polymer properties in polybutadiene. I. Preparation and characterization
Authors: Berger M. , Buckley D. J. 
Published: April 2003

AbstractStereoregular polybutadienes, of both high trans and high cis contents, were isomerized to provide polymers of varying cis‐trans content. These isomerizates were used to study structural effects on physical properties. The isomerizations were carried out under photosensitized conditions in benzene solution at 25°C. The reaction was controlled to deliver polymers over the range 0–95% trans content. This range was selected to provide crystalline and semicrystalline polymers whose structures could be examined in terms of sequencing or blocking by established x‐ray techniques. Isomer contents were measured accurately by infrared traces. Isomerizations reached an equilibrium of 77% trans regardless of whether the reaction started with high trans or high cis polybutadienes. Intrinsic viscosity was found to increase regularly with trans content in conformity with the larger size of the trans unit. ηsp/c versus c relations were observed to give a complicated form and this subject was deferred for further study. Crystallinity decreased regularly with reduced trans content as the equilibrium of 77% trans was approached. Continued isomerization at the point of equilibrium produced a completely amorphous polymer. The melting temperatures of the crystalline polymers were studied in detail by x‐ray camera and counting techniques. These polymers exhibited two crystal forms. One form was stable up to 60°C. and invariant with cis‐trans content in the range 80–95% trans. Below 80% trans the melting point of this form decreased with further reduction in trans content. The melting temperature of the other crystal form was dependent on trans content and decreased with decreased trans content until it coincided with the melting temperature of the other form. The distributions of trans and cis units and sequences of them were calculated through construction of matrices of transition probabilities. Copolymer theory was invoked to calculate pseudo reactivity ratios for the trans and cis forms. The melting temperatures of the two crystals were found to follow the predicted curves for random copolymers, although not simultaneously. This behavior is discussed. The crystallinity of the isomerizates of high trans content was found to be similar to block copolymers in spite of the fact that the method of their preparation would require that they be characterized as random. The importance of a crystal transition in this case is stressed along with the general effects due to the amount and type of the noncrystallizable unit.
Etude dela polyméarisation des oléafines catalysee par les oxydes méatalliques. I. Méathodes expéarimentales d'etude cinéatique; réasultats préaliminaires sur la polymégrisation du propylégne par le systégme catalytique phillips
Authors: Guyot Alain , Daniel Jean‐Claude 
Published: April 2003

AbstractThe kinetics of propylene polymerization catalyzed by chromium oxide on an aluminium silicate carrier was studied by a new method involving use of gas chromatographic analysis of samples removed from the monophase fluid medium surrounding solid catalyst and containing monomer and propane, without any other solvents. The apparatus and experimental methods are described in detail. The reaction is first‐order with respect to monomer, and also to catalyst if its concentration is high enough. Between 80 and 120°C, the activation energy is 16 kcal./mole. The polymerization rate depends on pressure only with respect to monomer concentration, but, when the pressure is low and the temperature high enough, a second process occurs which causes formation of volatile oligomers and retardation of normal polymerization process. The influence of catalyst and carrier structure and texture will be the subject of a subsequent study.
On Co60 gamma ray‐initiated emulsion polymerization
Authors: Acres G. J. K. , Dalton F. L. 
Published: April 2003

AbstractA study has been made of the Co60 γ‐ray‐initiated polymerization of methyl methacrylate and styrene; conversion rates have been measured by a dilatometric method. The dependence of polymerization rate on monomer concentration and radiation intensity has been determined for each monomer. It has been shown that the emulsion polymerization of methyl methacrylate can be described by accepted theories of emulsion polymerization; in the case of styrene a dependence of intensity exponent on monomer concentration has been found. Such a dependence does not occur when conventional initiating systems are used, and cannot be explained without some modification of theory.
Some viscoelastic studies on penton
Authors: Sharma M. G. , Haas T. W. 
Published: April 2003

AbstractStress relaxation tests on Penton polymer were conducted at various initial strain rates and initial strains. The data indicates that Penton is a nonlinearly viscoelastic material for the range of values of stresses and strains considered. It is found that the course of the relaxation depends considerably on the initial strains rates employed to attain a particular initial strain in a relaxation test. For the range of initial strain rates considered, the relaxation function can be represented as a function of the time ϕ(t) and by a power function of the strain rate ε0 of the type Ψ(t,ε0) = ϕ(t)(ε0)n. From the relaxation tests conducted at the same initial strain rate and for various initial strains, the relaxation stress σ for Penton can be expressed by the relation: σ = σ0 (1 − k log t), where σ0 is the stress at 1 min., t is the time, and k is a material constant.
The diffusion of chrysophenine G into viscose sheet
Authors: Warwicker J. O. 
Published: April 2003

AbstractAn experimental investigation into the diffusion of a direct dye into the edges of a viscose sheet is described. The results of these experiments are used to test the diffusion‐adsorption theory of Standing, Warwicker, and Willis. It is shown how this theory can be extended to allow for the effect of sodium chloride concentration on the diffusion coefficients.
Evaluation of molecular weight averages resulting from random crosslinking and chain scission processes for wide schulz‐zimm distributions
Authors: Kotliar A. M. 
Published: April 2003

AbstractThe Monte Carlo sampling technique was used to evaluate the resulting molecular weight averages and the intrinsic viscosity for wide Schulz‐Zimm distribution polymers, in the range P̄w/P̄n ≦ 11, undergoing random chain scission and crosslinking processes. The results may also be used to evaluate the initial distribution and are generally more reliable than the use of fractionation data.
General theory of stationary random sequences with applications to the tacticity of polymers
Authors: Coleman Bernard D. , Fox Thomas G 
Published: April 2003

AbstractWhen, in a poly‐α‐olefin, the probability that a given placement be isotactic depends upon the tacticity of only a finite number of immediate predecessors, the resulting diastereosequence distribution obeys the theory of Markoff chains. When this is not the case, one says that the resulting diastereosequence distribution is non‐Markoffian. A special case of a Markoffian distribution is given by a simple Markoff chain in which the tacticity of a given placement is assumed to be affected by only the tacticity of the immediately preceding placement. Another special case is, of course, the Bernoulli trial distribution in which the probability that a given placement be isotactic is independent of the tacticity of all other placements. A high resolution NMR spectrum can sometimes yield a quantitative determination of the concentrations of isotactic and syndiotactic placements and the concentrations of the three types of possible adjacent pairs of such placements (i.e., isotactic, syndiotactic, and heterotactic pairs). When this is the case, the spectrum can be used to determine whether or not a given diastereosequence distribution is Bernoullian. However, because the longest diastereosequences whose concentration can be measured by NMR spectroscopy involve only two placements, an NMR spectrum cannot check whether a given non‐Bernoullian distribution be simple Markoffian or Markoffian in general. In fact, non‐Markoffian distributions are compatible with existing NMR spectra on polymers prepared by anionic polymerizations. In this paper we work within the framework of Kac's theory of stationary statistical processes and point out some general results which are valid for both Markoffian and non‐Markoffian processes. The results are applied to NMR spectroscopy and it is pointed out which calculations used to check the self‐consistency of NMR data and to obtain the mean length of closed diastereosequences are valid for both Markoffian and non‐Markoffian distributions.
Colligative properties of polyelectrolyte solutions in excess of salt
Authors: Alexandrowicz Z. , Katchalsky A. 
Published: April 2003

AbstractThis work treats the equilibrium properties of polyelectrolyte solutions containing an excess of low molecular salt. In this case the simple rule of additivity, dealt with previously, fails to describe the experimental results. A detailed treatment, based on an approximate solution of the Poisson‐Boltzmann equation, was therefore undertaken. The calculation is based on a subdivision of the electrostatic potential into two parts corresponding to two regions: (1) an inner region in the close neighborhood of the polyion, free of coions and described by the Poisson‐Boltzmann equation in the salt‐free case, and (2) an outer region screened off from the central macroion and adequately treated by a Debyean approximation. An analytical solution for the electrostatic potential was obtained and used for the theoretical description of potentiometric behavior, Donnan distribution of salt, and Donnan osmotic pressure. The predicted values compare favorably with the measured results in a wide range of experimental conditions.
Interpretation of the intrinsic viscosity of polymers undergoing simultaneous degradation and crosslinking
Authors: Inokuti Mitio , Dole Malcolm 
Published: April 2003

AbstractAn attempt is made in this paper to calculate G values for simultaneous crosslinking and degradation during irradiation of polymers with side chains. Equations are given for the change in the weight‐average to number‐average molecular weight ratio as a function of dose for the case of degradation only. It is shown that the change in the logarithm of this ratio with the square root of the dose goes through a broad maximum over a certain dose range. This result coupled with estimates of Katsuura of the effect of branching on the intrinsic viscosity is used to explain the relationship discovered by Keyser, Clegg, and Dole between the logarithm of the intrinsic viscosity and the square root of the dose. It is concluded that the G value for degradation must change with dose; in the case of poly‐1‐hexene, for example, it is believed that G(S) falls from an initial value of about 0.15 to about 0.04 at high doses. Similar conclusions result from an application of the equations to polypropylene, but with higher values of G(S), about 1.1 initially and dropping about tenfold at doses above the gel point.
Kinetics of nucleation and growth of spherulites in homopolymers
Authors: Limbert Frank J. , Baer Eric 
Published: April 2003

AbstractIn order to check secondary nucleation theories previously proposed by various authors, spherulitic growth rates of polypropylene, high density polyethylene, and polyoxymethylene were measured at temperatures relatively close to their respective polymer melting points in an air circulating system with temperature fluctuations of less than ±0.05°C. Only partial agreement between theory and experiment was obtained. Interpretation of the experimental data using the similar theories of Burnett and McDevitt, and Barnes and co‐workers, gave melt‐spherulite interfacial energies which to date have not been checked by independent experiment. The critical surface tension of wetting as defined and measured by Zisman and co‐workers was compared with the melt‐spherulite interfacial energy and found in all cases to be substantially larger. The theory of Hirai, which is partially based on the absolute reaction rate theory of Eyring, was also tested, and heats of fusion which were about twice as large as values reported in the literature were found. A major shortcoming of all three nucleation theories is that the intercepts of the theoretical plots differed by many orders of magnitude for the various polymers tested. These theories do not give an adequate theoretical explanation of this fact. Thermal history of the melt was found to have a marked effect on the nucleation rate in polyoxymethylene. This implies that the overall rate constant in the Avrami theory is also strongly dependent on melt history. The data indicated that the rate constant can be decreased about five hundred times by increasing the melt temperature by 20°C.
Monomers containing phosphorus. Part I. Copolymerization of phosphonates with n‐lauryl methacrylate
Authors: Beynon K. I. 
Published: April 2003

AbstractThe reactivity ratios for the copolymerization of lauryl methacrylate (LMA) with diallyl phenylphosphonate (DAPP), diallyl butylphosphonate (DABP), and diethyl allylphosphonate (DEAP), respectively, have been measured at 80°.

None of the phosphonates are active for copolymerization with LMA but the DAPP and DABP have similar activities which are greater than that of DEAP. The variation with conversion in composition of the LMA‐DAPP copolymer formed at any instant has been calculated using Skiest's equation and the calculations have been extended to show the variation of the overall composition of the copolymer with conversion. Intrinsic viscosities and molecular weights have been measured for some LMA‐DAPP copolymers and these values are found to depend on the phosphorus contents of the copolymers.
Copolymerization of aldehydes
Authors: Mark H. F. , Ogata N. 
Published: April 2003

AbstractCopolymerization of aldehydes has been carried out in the presence of anionic and cationic catalysts. Triisobutylaluminum gave an elastic copolymer of formaldehyde and acetaldehyde which did not melt until above 300°C. and did not dissolve in any organic solvents. The rate of the copolymerization of formaldehyde and acetaldehyde at −78°C. was very rapid, the reaction going to completion within 30 min. The thermal stability of the copolymer of formaldehyde and acetaldehyde was better than that of polyacetaldehyde but was inferior to that of polyformaldehyde; it reaches a minimum in the composition range of 40/60 to 60/40 of formaldehyde and acetaldehyde.
Molecular properties of amorphous high polymers. II. An interpretation of gaseous diffusion through polymers
Authors: DiBenedetto A. T. 
Published: April 2003

AbstractA cell model is extended in order to interpret gaseous diffusion data through thin films of amorphous polymers. An amorphous polymer is again characterized as a homogeneous one component phase containing N identical n‐center polymer segments. A sorbed gas molecule is visualized as occupying an equilibrium position in a homogeneous lattice and behaving as a three dimensional harmonic oscillator trapped by surrounding bundles of parallel polymer segments. A diffusion “jump” is assumed to occur when four parallel polymer segments separate sufficiently to create a cylindrical void into which the gas molecule can move. Equations are developed which relate the activation energy for gaseous diffusion, the activation energy for self diffusion and the length of an average polymer segment to the molecular properties of the polymer. Gaseous diffusion data from various literature sources are successfully analyzed on this basis.
Thermodynamics of crystalline linear high polymers. III. Thermal breakdown of the crystalline lattice of polyethylene
Authors: Wunderlich Bernhard , Sullivan Peter , Arakawa Tamio , Dicyan A. B. , Flood J. F. 
Published: April 2003

AbstractThe thermal breakdown of the crystalline lattice of polyethylene grown by quenching from solution (dendrites) and by cooling slowly from solution (single crystals) and melt has been investigated as a function of heating rate. The dendrites showed strong reorganization at temperatures only little above the crystallization temperatures. Heating rates as fast as 20°C./min. could not avoid this reorganization. Heating rates between 10 and 20°C./min. were necessary to have a constant melting point for single crystals grown from solution. The measured melting points were proportional to the thickness and perhaps the density of the samples as determined by interference microscopy and by the density gradient column method. Surface free energy values calculated from the lowering of the melting points range from 81–96 ergs./cm.2. Literature values on specific heats and specific volumes of bulk samples allowed a discussion of the premelting behaviour of semicrystalline polyethylene. It is found that the defects frozen‐in below the glass transition temperature “grow” above 250°K. depending upon the overall crystallinity. This destroys the additivity of the specific heat as well as the specific volume. Correlation with NMR and dynamic mechanical loss measurements are attempted. The difference between melting and dissolution temperature in toluene (0.5–8.0 mg. polyethylene/g. toluene) for slowly cooled bulk as well as solution crystals was found to be 26°C., placing the maximum dissolution temperature of polyethylene crystals in toluene at 111°C.
Ionic polymerization of diphenylvinylphosphine oxide
Authors: Allcock H. R. , Kugel R. L. 
Published: April 2003

AbstractGrignard reagents, organolithium compounds, sodium naphthalene and aluminum alkyl—metal halide catalysts were examined as initiators for the polymerization of diphenylvinylphosphine oxide. The most effective catalysts studied were Grignard reagents and sodium naphthalene. With Grignard catalysis, polymers of molecular weight up to ∼10,000 were produced although the yield, molecular weight, and crystallinity of the products were influenced by the organic and halide components of the catalyst and by the reaction solvent. Copolymerization studies indicated that the anionic reactivity of diphenylvinylphosphine oxide is between those of styrene and methyl methacrylate. For Grignard catalysis an anionic‐type polymerization mechanism is proposed which requires the formation of polymer—organomagnesium halide adducts in the transition state.
Oxine–formaldehyde polymers and their metallic chelates
Authors: Horrocks Robert H. , Winslow Eugene C. 
Published: April 2003

AbstractSulfuric acid, sodium hydroxide, formic acid, and oxalic acid were investigated as catalysts for the condensation of oxine with formaldehyde. All were found to promote the condensation in aqueous solution under conditions of reflux, although a variation in the time required was found. The condensation was effected without catalyst between 200–240°C. in a sealed container by intimately mixing oxine with paraformaldehyde. Oxine–formaldehyde condensation polymers are soluble in phenol and acids stronger than acetic acid. Chelation is obtained by dissolving the polymer in acid, adding a solution containing the ion to be chelated, and adjusting the pH of the mixture to a value sufficiently high so as to favor chelation but not so high as to precipitate the metallic hydroxide. Heat stability was determined by thermogravimetry and differential thermal analysis. All samples degraded (began to lose weight) at 270°C. or below. The mode of decomposition of the polymer chelates appears to be independent of the metallic ion, but the free polymer is different. Its initial weight loss (between 270 and 320°C.) is very gradual compared to the chelates. At 320°C. it reverts to a form similar to that of the chelate. A second difference of the free polymer is that the rate of decomposition is a function of temperature, while that of the polymer chelates is not. The chelates may therefore hold interest in use as ablative materials. A third difference is that the free polymer melts beginning at about 190°C. The chelates do not melt.
Thermal degradation ofN‐substituted polycarbamates
Authors: Dyer Elizabeth , Hammond Richard J. 
Published: April 2003

AbstractN‐substituted polycarbamates of relatively low molecular weight have been prepared from the condensation of 1,6‐hexanebischloroformate withN‐substituted diamines, both aliphatic and aromatic. The initial rates of thermal degradation of these polymers and of unsubstituted analogs have been determined at 230–285°C. by following the evolution of carbon dioxide. The results showed that the more thermally stable polymers were those derived from the substituted aliphatic diamines, having the formula [N(R)XN(R)COO(CH2)6OCO]nwhere X is (CH2)5or (CH2)6. When R was CH3and C6H5, the overallEAwas 31 and 46 kcal./mole, respectively. The polymers derived from aromatic diamines, where X was 4,′ 4‐C6H4CH2C6H4, showed low values forEA, approximately 15 kcal./mole, regardless of whether R was H or alkyl. This low thermal stability was shown to be caused by amine endgroups. Some evidence as to modes of thermal degradation was obtained from a study of volatile products.
Preparation and properties of poly(tetramethyl‐p‐silphenylene‐siloxane)
Authors: Merker Robert L. , Scott Mary Jane 
Published: April 2003

AbstractImproved methods for the synthesis of p‐bis(dimethylhydroxysilyl)benzene are described. This useful monomer was prepared from p‐bis(dimethylhydrogensilyl)‐benzene which was obtained in 60–70% yields from p‐dibromobenzene and dimethyl chlorosilane by use of an in situ Grignard technique. The great reluctance due to steric factors of the p‐silphenylene‐siloxane configuration to form cyclic structures has been amply demonstrated. The condensation polymerization of p‐bis(dimethylhydroxysilyl)benzene in benzene solution has yielded high molecular weight, crystalline poly‐(tetramethyl‐p‐silphenylene‐siloxanes). The heat of fusion ΔHu of the tetramethyl‐p‐silphenylene‐siloxane was found to be 4350 cal./unit. The modified Staudinger equation relating intrinsic viscosity and weight‐average molecular weight was applicable over a range of 70,000–400,000. These results are summarized in the relationship, [η] = 1.12 × 10−4Mw0.75. Tetramethyl‐p‐silphenylene‐siloxanes were found to be more stable than dimethylsiloxanes both to atmospheric oxidation and degradation through volatile formation in the temperature range 200–305°C.
Preparation and polymerization of 1,5‐diamino‐2,4‐alkylenetrisilazanes
Authors: Breed L. W. , Elliott R. L. , Ferris A. F. 
Published: April 2003

Abstract1,5‐Diamino‐2,4‐ethylenehexamethyltrisilazane and related compounds were prepared by treating the corresponding chlorosilane intermediates with ammonia or an amine. When these monomers were heated in xylene solution at 140°C. in the presence of ammonium sulfate, linear silicon‐nitrogen polymers were obtained with molecular weights in the range of 7,500–15,000. Elemental analyses, infrared spectra, and the physical properties of the polymers support the proposed structure and polymerization route.
Kinetics of the photopolymerization of tetraethylene glycol dimethacrylate in the bulk with the use of desyl aryl sulfides as photoinitiators
Authors: Petropoulos Constantine C. 
Published: April 2003

AbstractFive desyl aryl sulfides were prepared for use as photoinitiators in the determination of the bulk polymerization rates of tetraethylene glycol dimethacrylate at 25°C. As a first approximation, the initial rates were first‐order with respect to monomer and one half‐order with respect to initiator. From this, approximate initial overall rate constants were determined. The data indicate that resonance stabilization of the dissociated radical seem to affect the polymerization rate. Complications arising from the auto catalytic gel effect were discussed.