bluuebunny/crossref_metadata_2025 huggingface dataset:
Mode of termination in the copolymerization of vinyl acetate–isobutyl methacrylate and methyl methacrylate–methyl acrylate at 60°C
Authors: Chaudhuri Ajit Kumar , Palit Santi R.
Published: April 2003

The mode of termination in the vinyl acetate–isobutyl methacrylate (VA–IBMA) and methyl methacrylate–methyl acrylate (MMA–MA) copolymerization systems has been investigated at 60°C. by using the dye‐interaction technique for functional endgroup estimation. The results show that pairs of poly(vinyl acetate) radicals interact almost exclusively through a disproportionation mechanism. In the homopolymerization of methyl methacrylate and methyl acrylate, about 1.16 and 1.22 carboxyl‐containing endgroups per polymer molecule have been estimated, which shows the predominance of disproportionation over combination in these termination reactions. In poly(isobutyl methacrylate) about 1.55 tagged initiator fragments per chain indicate that 29% of the total radicals terminate through the disproportionation mechanism. Cross termination in the (VA–IBMA) copolymerization system occurs almost entirely through combination for monomer feeds richer in isobutyl methacrylate content while for the MMA–MA system, combination is more important at intermediate monomer feed ratios. These results have been discussed in the light of different explanations for the reaction mechanism.
Heterogeneity parameters by light scattering for statistical copolymers incorporating long side‐chain comonomers
Authors: Jordan Edmund F.
Published: April 2003

Heterogeneity parameters were obtained by light scattering for a series of statistical copolymers incorporating long side‐chain comonomers, by employing the method of Bushuk and Benoit. These copolymers were selected to exhibit varied compositional drift as required by copolymerization theory. The magnitude of the parameters found agreed qualitatively with the heterogeneity expected from the drift in composition with conversion. This was calculated using the treatment of Skeist, as modified by Kruse. However, values greater than the limit of unity were found in two instances for the heterogeneity index, Q/Qmax, which relates the compositional drift constant Q to the maximum value obtained for mixtures of homopolymers. These anomalies were attributed to the insensitivity of the method for heterogeneous copolymers having small differences in the refractive increaments of their respective homopolymers. The magnitude and sign of P, which reflects molecular weight effects on composition, was questionable because of experimental error. Both effects appear to be general deficiencies of the method, which limit its practical use. For solvents with high values of dn/dc (≈0.1), the observed weight‐average molecular weight approached the true value.
Polymerization of 2‐(chlorinated methyl)‐4‐methylene‐1,3‐dioxolanes
Authors: Dietrich Heinz J.
Published: April 2003

The polymerizations of the novel 2‐(chlorinated methyl)‐4‐methylene‐1,3‐dioxolanes derived from mono‐, di‐, and trichloroacetaldehyde were investigated. Poly‐2‐trichloromethyl‐4‐methylene‐1,3‐dioxolane was of particular interest because of its high hydrolytic stability and nonflammability. The monomers could be polymerized with cationic catalysts via the methylene functions without cleavage of the dioxolane rings. This selectivity was due to the acetal‐stabilizing negative substituents and to the use of Lewis acid complexes of low reactivity as catalysts. In contrast to previously reported poly‐4‐methylene‐1,3‐dioxolanes, the title polymers were high‐melting colorless solids of good to excellent fire resistance.
Polymers from 1,3‐dipole addition reactions: The nitrilimine dipole from acid hydrazide chlorides
Authors: Stille J. K. , Harris F. W.
Published: April 2003

An investigation of the suitability of the 1,3‐dipole addition reaction of bisnitrilimines, generated from the corresponding acid hydrazide chlorides, with diyne and dinitrile dipolarophiles was carried out. The reactions of iso‐ and terephthaloylphenylhydrazide chlorides and 4,4′‐oxydibenzoylphenylhydrazide chloride with the dipolarophiles m‐ and p‐diethynylbenzene, m‐divinylbenzene, and perfluoroglutaronitrile in the presence of triethylamine gave moderate molecular weight polymers containing pyrazole or triazole units along the polymer backbone. The polymers were soluble in such polar solvents as hexamethylphosphoramide and acids but had inherent viscosities only as high as 0.32. The thermogravimetric analyses of the finely powdered polypyrazoles showed breaks near 500°C. in air and in nitrogen atmospheres.
Fluorine magnetic resonance spectra and tacticities of poly(vinyl trifluoroacetate)
Authors: Fujii K. , Brownstein S. , Eastham A. M.
Published: April 2003

Fluorine magnetic resonance spectra of poly(vinyl trifluoroacetate) samples of different tacticities were investigated, along with those of model compounds. These polymers represent the first case where the line order in respect to stereostructure does not agree with that expected from the spectra of model compounds. More than four peaks were observed for signals from the trifluoromethyl groups of the polymers and the relative peak positions differed from those previously reported. The intensity ratios of the peaks were affected by the solvent employed. Therefore the spectra cannot be interpreted in terms of triad stereosequences. Seemingly longer stereosequences or other influences have to be considered to interpret the spectra.
Studies on the charge transfer complex and polymerization. XIV. Spontaneous copolymerization of 1‐methylcyclopropene and sulfur dioxide
Authors: Iwatsuki Shouji , Kokubo Takashi , Yamashita Yuya
Published: April 2003

Copolymerization between 1‐methylcyclopropene (MCP) and sulfur dioxide (SO2) was studied. It took place spontaneously even at a low temperature, and was found to be consistent with polymerization by a “living” radical, as suggested by the increase of reduced viscosity with conversion and by the formation of block polymers in the presence of acrylates. The rate of copolymerization was proportional to [MCP]3 and [SO2]2, and the overall activation energy of copolymerization was about 15.1 kcal/mole. A tentative mechanism to explain the experimental results is discussed.
Synthesis and polymerization studies of several chloro and cyano epoxides
Authors: Wei Peter E. , Butler Peter E.
Published: April 2003

The polar epoxides, glycidonitrile, dimethyl glycidonitrile, tetracyanoethylene oxide, epicyanohydrin, 4,4,4‐trichlorobutylene‐1,2‐epoxide, and 1,1‐dichloro‐3,4‐epoxy‐1‐butene were prepared, characterized by their infrared and nuclear magnetic resonance spectra and their polymerizations studied. Epicyanophydrin was found to be an unpolymerizable dimer, and those epoxides with a cyano group attached directly to the epoxide ring could not be polymerized. The halogenated epoxides, 4,4,4‐trichlorobutylene‐1,2‐epoxide and its dehydrochlorination product, 1,1‐dichloro‐3,4‐epoxy‐1‐butene were polymerized to high polymers with a complex catalyst from aluminum alkyl, acetyl acetone, and water. The polymerization of these monomers gave low conversions and required large amounts of catalyst. Higher conversions were obtained by copolymerization with propylene oxide or terpolymerization with propylene oxide and allyl glycidyl ether. The polymerizability of the substituted epoxide in (where X is CH3, ClCH2, Cl3CCH2, and Cl2CCH) was found to follow the order: CH3 > ClCH2 > Cl3CCH2 > Cl2CCH. The polymers of 4,4,4‐trichlorobutylene‐1,2‐epoxide and its dehydrochlorination products were not vulcanizable through the chlorine functionality or the olefinic unsaturation of the type Cl2CCH. The presence of an active third monomer such as allyl glycidyl ether was necessary to facilitate vulcanization. Properties of such vulcanizates are reported.
Salt effects in the base‐catalyzed polymerization of unsaturated amide compounds. II. Polymerization of p‐vinylbenzamide and acrylamide
Authors: Asahara Tomohiko , Yoda Naoya
Published: April 2003

In the presence of a variety of inorganic salts, p‐vinylbenzamide underwent vinyl‐type polymerization by anionic initiators to form the polystyrene derivative, whereas in dimethyl sulfoxide as solvent the aromatic polyamide was always obtained through a proton‐transfer mechanism regardless of the presence of the salts.
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In the presence of of the salts, acrylamide is generally polymerized to the polyamide through a proton transfer reaction.
X‐ray degradation of penton and its potential use as a dosimeter for the 4–15 keV range
Authors: Mallon Barbara J.
Published: April 2003

Exposure of poly‐3,3‐(bischloromethyl)oxetane (Penton) to x‐rays produces a linear reduction of the molecular weight, heat of fusion, and melting point with increasing absorbed dose. Optical density measurements fit a smooth curve with absorbed dose. Exposures were made with 25, 50, and 100 cal/cm2 integrated incident energy at 50 peak kV with and without zinc and titanium‐aluminum filters. Because the molecular weight of Penton is relatively uniform from lot to lot, and because it is difficult to obtain spectral measurement in the 4–15 keV range to which Penton is particularly sensitive, it is believed that the data contained in this report can be used with an interative computer code to determine the spectrum and intensity of radiation in this region.
Macroreticular resins. III. Formation of macroreticular styrene–divinylbenzene copolymers
Authors: Kun Kenneth A. , Kunin Robert
Published: April 2003

Experimental evidence is presented that describes the mechanism of formation of macroreticular styrene–divinylbenzene copolymers in which phase separation occurs during a suspension polymerization. The mode of formation of the macroreticular structure is described as a three‐stage process in which each droplet of the organic phase behaves as an individual in a bulk polymerization that results in a bead of copolymer. Macroreticular structure formation is described by changes in copolymer swelling ratios, infrared absorption spectra of vinyl groups pendent to the polymeric matrices, surface area, total porosity, and pore‐size distribution. The proposed mechanism of formation is also substantiated by electron micrographs of the copolymers during various stages of the copolymerization.
Wide line and pulsed NMR studies of carboxyl‐terminated polybutadiene polymers and binders
Authors: Tompa A. S. , Barefoot R. D. , Price E.
Published: April 2003

Nuclear magnetic resonance relaxation and line width studies were performed on two carboxyl‐terminated polybutadiene polymers and their corresponding binders at temperatures from −170 to 25°C. It was observed that the line widths of the binders increased as the functionality of the corresponding liquid polymers increased. In addition, glass transition temperatures and activation energies obtained from line width measurements were determined. From pulse measurements the magnitude of the relaxation time T1 and the temperature at which T1 is a minimum were determined for a polymer and its corresponding binder. These empirical quantities for the carboxyl‐terminated polybutadiene polymers were lower than those of the corresponding binders because of less restraints in the internal motions of the polymer chain.
Molecular weight distributions in polymerizing systems with different coexisting active centers
Authors: Bresler S. E. , Brussalimsky B. L. , Kulevskaya I. V.
Published: April 2003

Polymerization of acrylonitrile initiated by organomagnesium compounds Bu2Mg or BuMgCl leads to almost monodisperse polymers. The molecular weight distribution (MWD) of these polymers is so narrow that it cannot be measured by means of the ultracentrifuge. It remains narrow till high conversions. On the other hand, initiation by complex Bu3Mg2I leads to polymers with a broad MWD. From kinetic measurements we know that this reaction is free of chain termination and chain transfer. Also the initiation of chains is practically immediate. The reason for broad MWD in this particular case is the coexistence of different growing centers of polymerization. The propagation constants for these centers are obviously different. If these different active centers can periodically undergo transition from one type into the other the MWD of resulting polymer chains will broaden. A very simple semiquantitative theory for this phenomenon was developed. It shows that the fewer exchanges between the coexisting centers that occur during the reaction time, the broader will be the MWD of the polymer chains. Hence it was concluded that the broadest MWD of products must be found at low conversions. With an increase of reaction time and conversion the MWD becomes more narrow. This peculiar prediction was corroborated by experiment.
Molecular structure of synthetic rubber. I. Light‐scattering properties of styrene–butadiene copolymers
Authors: Bahary William S. , Bsharah Lewis
Published: April 2003

The discrepancy between the values reported for the weight‐average molecular weight and molecular weight distribution of cold‐type styrene‐butadiene rubber is examined. The results obtained indicate that aggregation of the rubber due to hydrogen bonding or cluster formation is not a contributing factor to the high weight‐average molecular weights obtained. The very broad molecular weight distributions, the M̄w/M̄n of the order of 10–20, are attributable to the presence of a few per cent of very high molecular weight fraction microgel in samples polymerized to moderate conversions. This microgel has been removed to various degrees by several methods: (1) mastication, (2) treatment with CaSO4, (3) ultracentrifugation, and (4) ultrafiltration. The nature of this microgel is examined in terms of its light‐scattering property, intrinsic viscosity, and concentrated solution viscosity. The weight‐average molecular weight obtained by light scattering on these samples after removal of microgel are lower by as much as an order of magnitude. The operational definition of the weight‐average molecular weight, M̄′w, is therefore introduced, corresponding to the one obtained after removal of the microgel. It is suggested that the actual and the operational weight‐average molecular weights be used in conjunction in the characterization of these copolymers.
Novel bridged anthracene derivatives and polyesters and copolyesters therefrom
Authors: Klanderman B. H. , Faber J. W. H.
Published: April 2003

9,10‐Bis(hydroxymethyl)triptycene, 9,10‐dihydro‐9,10‐bis(hydroxymethyl)‐9,10‐ethanoanthracene, 9,10‐dihydro‐9,10‐bis(hydroxymethyl)‐9,10‐(2,3‐bicyclo[2.2.1] heptano)‐anthracene, 9,10‐dihydro‐9,10‐bis(hydroxymethyl)‐N‐phenyl‐9,10‐ethanoanthracene‐11,12‐dicarboximide, and 9,10‐bis(carbethoxy)triptycene have been prepared and employed as modifying agents to improve the physical properties of polyesters such as poly(ethylene terephthalate). Especially noteworthy are the high glass transition temperatures (Tg) which can be obtained.
Studies on the polymerization of bifunctional monomers. XVI. Cyclopolymerization of o‐divinylbenzene with triphenylmethyl fluoroborate and presumption of the presence of the free growing cation in this system
Authors: Aso Chuji , Kunitake Toyoki , Matsuguma Yoshihiko , Imaizumi Yoji
Published: April 2003

Cyclopolymerization of o‐divinylbenzene was studied by using triphenylmethyl fluoroborate as initiator. The cyclization constant rc (ratio of the rate constant for intramolecular cyclization to that for intermolecular propagation) decreased with increase in polarity of the solvent. This solvent effect as well as the effect of catalysts reported previously could be accounted for by a revised model of the propagating species, where both the counter anion and the o‐vinyl group were coordinated to the carbonium ion. The difference in activation energy between intramolecular cyclization and intermolecular propagation was 6.2 kcal/mole. This value was close to that obtained previously with BF3·OEt2 catalyst but greater than those for anionic and radical polymerizations. When tetraalkylammonium flouroborates were added to the polymerization system in methylene chloride, rc and the molecular weight of the polymer decreased. These results were ascribed to the decrease in the amount of the free propagating cation by the common ion effect.
Electron‐transfer polymers. XXXIV. Redox polyurethanes from p‐benzoquinone‐2,5‐diols and diisocyanates
Authors: Wegner Gerhard , Nakabayashi Nobuo , Cassidy Harold G.
Published: April 2003

It is possible to prepare polyurethanes from p‐benzoquinone‐diols and diisocyanates by using dibutyltin diacetate catalyst at room temperature or below, since the benzoquinone group does not react with isocyanate under these conditions. This permits preparation of new redox polymers. In preparing the polyurethanes excess isocyanate groups must be destroyed at the end of the reaction time in order to prevent crosslinking during work‐up. These polymers are readily reduced by aqueous hydrosulfite. Good viscosity numbers are obtained; and, in general, upon reduction the viscosity increases over that of the oxidized form. There is no evidence of crosslinking. When oxidized and reduced forms of these polymers are mixed there is no evidence of charge transfer.
Polymerization of vinylcyclopropanes. III. Cationic polymerization of stereoisomers of 1‐halo‐2‐vinylcyclopropanes
Authors: Takahashi Takako
Published: April 2003

Vinylcyclopropane derivatives, 1‐chloro‐ and 1‐bromo‐2‐vinylcyclopropane, have respectively two stereoisomers, and radical polymerizations of both isomers gave 1,5‐type polymers. On the other hand, only the cis isomers gave a polymer which had mainly 1,2‐type structural units in cationic polymerizations with Lewis acids. The difference between the cationic polymerizabilities of the cis and trans isomers is interpreted in terms of steric conformation of monomers.
Statistical thermodynamics of polymer solutions. VI. Comblike branched molecules with branches placed randomly along the backbone
Authors: Casassa Edward F. , Tagami Yukiko
Published: April 2003

Thermodynamic interactions between arbitrarily branched flexible “comb” molecules (with branches of uniform length affixed to backbones of uniform length but with the number of branches on a molecule and their placement arbitrary) are treated by Zimm's perturbation method to obtain results valid to the double contact approximation. Thus, bimolecular cluster configurations with one and two intermolecular contacts, but not more, are correctly accounted for. This general result is applied to “random” combs (with the number of branches per comb uniform, but the placement random) and to “heterogeneous” combs (with both the number of branches on a molecule and their placement random). Results for the random combs are very similar to those reported earlier for “symmetrical” combs (with f uniform branches disposed at points along the backbone chain so as to subdivide it into f + 1 equal sections), but the second virial coefficient for the random model is slightly the larger when the number of branches per chain is small and the fraction of the molecule in the backbone is at least a few per cent. Since random combs are uniform in mass, the osmotic pressure and light‐scattering second virial coefficients are alike; but for a system of heterogeneous combs the virial coefficients differ from one another, and from the random comb result, when the mean number of branches f̄ per chain is small and they are of appreciable length in comparison to the backbone. This behavior reflects the heterogeneity in both molecular mass and dimensions existing under these circumstances. As f̄ increases and/or the mean fraction of segments in the chain backbone becomes large, coincidence with the random comb result is approached. The double‐contact second virial coefficients for both random and heterogeneous combs are obtained in closed analytical expression that are much more easily reduced to numerical results than the expression for symmetrical combs given earlier. These two models also correspond better than the symmetrical combs to materials actually obtainable.
Molecular weights and molecular weight distribution of polymers by equilibrium ultracentrifugation. Part II. Molecular weight distribution
Authors: Scholte Th. G.
Published: April 2003

A method has been developed for determining the molecular weight distribution of a polymer sample from the sedimentation–diffusion equilibrium data for a solution under pseudo‐ideal conditions. From some theoretical examples it appears that the method works well and that the molecular weight distribution can be determined with a reasonable degree of resolution. From three polymer samples (polyethylene, polystyrene, and polycaprolactam) the molecular weight distribution was determined in this way. The average molecular weights, M̄n, M̄w, M̄z, and Mz+1, calculated from these distribution functions agree well with those calculated directly from the equilibrium data.
Flow birefringence and polydispersity
Authors: Daum U.
Published: April 2003

Flow birefringence data for dilute solutions of various linear and branched polymers of different degrees of polydispersity are discussed. The polymers considered are polystyrene, polypropylene, and polyethylene. By making use of a well‐known stress‐optical relation, reduced elastic normal stresses, which can also be interpreted as coil expansions, are plotted against reduced shear stresses. As elastic normal stresses are rather sensitive to the shape of the molecular weight distribution at high molecular weight, a characteristic, p, related to the skewness of the distribution, is obtained. Experimental values of p are compared with theoretical ones based on special types of distribution functions. Attention is paid to the method of extrapolating experimental results to zero shear stress and concentration.
Crystallization kinetics of stretched natural rubber
Authors: Kim Hyo‐Gun , Mandelkern L.
Published: April 2003

Studies of the crystallization kinetics of natural rubber networks held in simple extension are reported. In these experiments the length of the specimen was held constant, and the crystallization process was followed by the decay in stress that occurred. A wide range of extension ratios and crystallization temperatures was encompassed by these experiments. From an analysis of the shapes of the crystallization isotherms, it can be concluded that major changes take place in the nucleation and growth processes as the extension ratio is increased. This conclusion is in accord with reports in the literature of changes in the crystallite morphology with extension ratio. Analysis of the temperature coefficient of crystallization, by means of nucleation theory, indicates a substantial increase in apparent interfacial free energies with increased deformation. This latter observation is interpreted to indicate a departure from a correlated crystallization process to one where isolated crystallites are formed.
Influence of microstructure on the hydrodynamic behavior of poly‐α‐methylstyrene
Authors: Cowie J. M. G. , Bywater S.
Published: April 2003

The theta temperature of poly‐α‐methylstyrene in cyclohexane has been found to vary with the stereostructure of the polymer. The observed values range from 305.5°K. for highly syndiotactic material (0.95 syndiotactic diads) to 310.0°K. for anio ically polymerized samples (0.67 syndiotactic diads). Results indicate that the unperturbed dimensions of the polymer increase with increasing isotacticity of the chain, whereas the entropy parameter ψ1, measured in cyclohexane, decreased as the structure became more isotactic. Measurements of the second virial coefficient in toluene showed an increasing interaction with the solvent as the polymer became more syndiotactic.
Identification of a stereoblock poly(methyl methacrylate) sample with a stereocomplex
Authors: Liquori Alfonso M. , Anzuino Giuseppe , D'Alagni Maria , Vitagliano Vincenzo , Costantino Lucia
Published: April 2003

Acid hydrolysis of a stereoblock poly(methyl methacrylate) sample leads to a mixture of isotactic and syndiotactic poly(methacrylic acid) which can be separated by electrophoresis. The experiment confirms the stereochemical identity between the so‐called “stereoblock” poly(methyl methacrylate) and the stereocomplex which syndiotactic and isotactic poly(methyl methacrylate) form in the ratio 2:1. A possible mechanism of replica polymerization is suggested to account for this effect.
Conformation and normal frequency distribution of polymer chains
Authors: Jannink G.
Published: April 2003

It is argued on the basis of a simple model for a polymer chain that characteristics of conformation can be determined from the analysis of the frequency distribution of backbone vibrations. In a chain with one degree of freedom per repeat unit, a fold tends to uncouple the motions on each side of the fold. This transfers highest and lowest modes towards the mean value. Conversely, a local unfolding of a random chain enhances the coupling and produces out‐of‐band modes. From the ordering of these modes, statistical aftereffects can be detected. The Green's function method allows a calculation of the single localized mode as a function of angular parameters. The dynamical matrix elements of the Kirkwood‐Pitzer model are calculated for a folded polyethylene backbone chain. The eigenvalue distribution is determined with the Givens‐Sturm procedure. It indicates a one‐to‐one correspondence between modes in the vicinity of 670 cm.−1 in the stretch‐bend gap and chain folds, for low concentration of folds. We conclude that conformations should have two characteristic parameters distinctively reflected in the frequency distribution, namely the range of allowed dihedral angles and the ordering of configurations along the chain. The frequency distribution for a given conformation depends however on the force constant ratios when the degree of freedom is greater than one. Interpretation of the frequency spectrum is then made by adjustment of dynamical and geometrical parameters. These are seen to be dependent variables with respect to the spectrum.
Load drop at the upper yield point of a polymer
Authors: Brown N. , Ward I. M.
Published: April 2003

The stress‐system curves have been measured for isotropic and oriented specimens of poly(ethylene terephthalate) in extension, shear, and compression. It was found that for all these types of deformations there was an intrinsic yield drop, i.e., a fall in true stress. It is concluded therefore that the stress for initiation is greater than the stress for propagation of yielding.
Distribution of tensile data of vulcanized rubbers. I. Tensile data of SBR vulcanizates loaded with light calcium carbonate
Authors: Yabuta Shiro , Kase Shigeo
Published: April 2003

When the first asymptotic probability function of smallest values was applied to analyze the distribution of tensile strength data for rubbers, good agreement between observed values and theory did not always result. In order to improve the agreement, use of another distribution function, the third asymptotic probability function, was proposed. Experiments verified that this function yielded good agreement with theory for the distribution of tensile strengths of rubbers, especially for SBR vulcanizates loaded with light calcium carbonate. The third asymptotic probability function contains three parameters: the characteristic value V, the lower limit ε, and the shape parameter k which is dimensionless. Analysis is made by use of a logarithmic extremal probability paper on which the probability function plots as a straight line if ε = 0. There appears to be a lower limit for the distribution of tensile strengths but not for the distribution of elongations. This suggests that the tensile properties follow the third asymptotic distribution function, with the breaking elongations following the simplified form of the Weibull distribution.
Studies of solution properties of copolymers. II. Copolymer of maleic anhydride and styrene
Authors: Endō Ryūichi , Hinokuma Teruo , Takeda Masatami
Published: April 2003

Styrene and maleic anhydride were copolymerized in benzene. The whole polymer thus obtained was fractionated with acetone and petroleum ether as the solvent and precipitant, respectively. The viscosities and osmotic pressures of the fractions were determined in tetrahydrofuran. The relation between the intrinsic viscosity and the molecular weight, [η] = 5.07 × 10−5 M̄n0.81, was obtained in tetrahydrofuran. The unperturbed mean square end‐to‐end distance was estimated by the Stockmayer‐Fixman equation. A theoretical equation for the mean square end‐to‐end distance for a chain of repeating units of different bond lengths a and b with a fixed valence angle θ and without restriction of internal rotation was presented and applied to this copolymer. In addition, the equation of the mean‐square end‐to‐end distance derived by Wall for trans‐polyisoprene without rotational restriction was modified for application to this copolymer. The result evaluated with our equation was about 26% smaller than that from the modified Wall equation. A steric parameter for the present copolymer is defined and discussed in comparison with those of polystyrenesulfone and polystyrene.
Solution properties of poly(methyl acrylate) and (1:1) poly(styrene‐co‐methyl acrylate)
Authors: Karunakaran K. , Santappa M.
Published: April 2003

Poly(methyl acrylate) (PMA) and 1:1 poly(styrene‐co‐methyl acrylate) (PSMA) were prepared by solution and bulk polymerization, respectively. The copolymer was analyzed with NMR to ascertain its composition and microstructure. The solution properties of unfractionated PMA and fractionated PSMA in ethyl acetate were investigated by light‐scattering and viscosity techniques at 35°C. Narrow composition heterogeneity as revealed from the light‐scattering measurements in different solvents justified the use of a single solvent for the copolymer characterization. The equations relating the limiting viscosity number to molecular weight, the molecular dimension to molecular weight, etc., were found for homopolymer and copolymers in ethyl acetate at 35°C. In the evaluation of the Flory constant K for the unperturbed state by methods based on Flory‐Fox‐Schaefgen, Kurata‐Stockmayer, and Stockmayer‐Fixman expressions, only the first method gave a value for PMA in ethyl acetate, consistent with that obtained in other solvents, whereas similar values of K were obtained by the three methods for PSMA in ethyl acetate. The studies indicate reduced thermodynamic interaction for PSMA–ethyl acetate compared to PMA–ethyl acetate, but increased steric effect in the copolymer compared with the homopolymer.
Unperturbed chain dimensions of isotactic polypropylene in theta solvents
Authors: Nakajima Akio , Saijyo Akira
Published: April 2003

The unperturbed mean‐square end‐to‐end distance 〈R02〉 and its temperature variation d In 〈R02〉/dT for isotactic polypropylene have been estimated from intrinsic viscosity data in three theta solvents, i.e., diphenyl, diphenyl ether, and dibenzyl ether, measured at their θ temperatures as determined by precipitation temperature measurements. The characteristic ratios, 〈R02〉/nl2, where n is the number of bonds of length l in the main chain, evaluated by assuming Φ = 2.87 × 1021, are 5.80 in diphenyl (at θ = 125.1°C.), 5.41 in diphenyl ether (at θ = 142.8°C.), and 4.56 in dibenzyl ether (at θ = 183.2°C.). These values lead to the temperature coefficient d In 〈R02〉/dT = −4.09 × 10−3 deg.−1 Results are compared with the data previously reported on polyethylene.
Nucleation of crystallization in molten isotactic polybutene‐1
Authors: Burns Joanne R. , Turnbull D.
Published: April 2003

Droplet experiments have been performed on polybutene‐1. It was found that this polymer can be cooled to room temperature without homogeneous nucleation of crystallization. It was also found that when the polymer was heterogeneously nucleated, form I (as well as form II) could be crystallized directly from the melt. The melting point of droplets crystallized in form I near room temperature decreased with increasing crystallization temperature, while the melting point of the droplets crystallized in form I at the highest temperatures increased with increasing crystallization temperature. There was a broad minimum at about 60°C. in the melting point versus crystallization temperature curve.
Crosslinked oligoethylene glycols: Correlation between their structure and some rheological properties
Authors: Katz Dov , Salee Gideon
Published: April 2003

Six oligoethylene glycols were crosslinked with triphenylmethane triisocyanate, and polymers with systematically changing network chain lengths were obtained and investigated. The 10‐sec. torsion moduli versus temperature, glass transition temperatures, and cohesive energy densities of the polymers were determined and studied. The 10‐sec. torsion modulus versus temperature plots show that all six polymers have a glassy transition and rubbery region of rheological behavior. The front factor calculated from the equation for the torsion modulus in the rubbery region when measured values of the modulus were used was compared with the front factor computed from equations that take into consideration molecular structures of the rubbery networks. With the exception of the case of crosslinked diethylene glycol the agreement in all the other cases between the values obtained for the front factor in both ways was good. In the investigated range of temperatures the polymers have below the glass transition temperature another transition point. The solubility parameters of the polymers, calculated from swelling experiments, were with the exception of the first member in the series almost identical.
Effect of x‐rays on extended chain crystals of polyoxymethylene
Authors: Jaffe M. , Wunderlich B.
Published: April 2003

Extended chain crystals of polyoxymethylene were irradiated with x‐rays of about 105 r./min. An immediate decrease in superheating on melting was noted. After 90 min. of irradiation the melting point level, refractive indices, and density also decreased. After 480 min. the DTA melting peak at a heating rate of 20°C./min. had decreased 25°C., the melting point decreased about 18°C., and the density calculated from refractive indices decreased 0.031 g./cm.−3. These effects are interpreted as indication of chain scission and formation of amorphous defects.
Heat capacities for atactic polystyrene of narrow molecular weight distribution to 360°K.
Authors: Chang S. S. , Bestul A. B.
Published: April 2003

Precise heat capacity values are reported over the temperature range from 10 to 360°K. for a sample of atactic polystyrene having a narrow molecular weight distribution. This sample was taken from the stock from which National Bureau of Standards Standard Sample 705, Narrow Molecular Weight Distribution Polystyrene, was established. Data are reported for the sample as received, and after an annealing procedure. At temperatures below about 60°K. a systematic difference comparable with the limits of experimental precision appears between the values obtained for the present sample as received and after the annealing, although at higher temperatures the values for the two conditions showed no systematic difference beyond the limits of precision of the measurements. At temperatures above 100°K., previously published values for atactic polystyrene samples of various molecular weight distributions and for isotactic polystyrene agree within about 0.5% of the values from this investigation. At temperatures below 100°K. significant heat capacity differences appear, especially between values for the atactic and the isotactic isomers, and even between atactic samples of different molecular weight distribution.
Crystallization kinetics of polymer–diluent mixtures. Influence of benzophenone on the spherulitic growth rate of isotactic polystyrene
Authors: Boon J. , Azcue J. M.
Published: April 2003

As an extension of earlier work on the crystallization kinetics of isotactic polystyrene, the spherulite growth rate in mixtures of isotactic polystyrene and benzophenone has been measured over a concentration range extending from pure polymer to a mixture containing about 30% benzophenone. The glass transition temperature has been measured over the entire range from pure polymer to pure benzophenone. For the mixtures the dependence of the growth rate on temperature is similar to that of the undiluted polymer. The addition of benzophenone causes a shift of the crystallization range to lower temperatures. For mixtures containing up to about 20% benzophenone, the maximum in the growth rate increases with increasing content of benzophenone. On addition of more benzophenone, the maximum rate is depressed. Taking into account the glass transition temperature of the mixtures, the influence of benzophenone on the melting point of isotactic polystyrene, and the volume fraction of polymer, we can describe the influence of benzophenone on the growth rate in a semiquantitative way.
Hydrogen bonding in butadiene copolymers. II. Network relaxation
Authors: Otocka E. P. , Eirich F. R.
Published: April 2003

The mechanical lability of intermolecular hydrogen bonds in stoichiometric mixtures of acidic and basic butadiene copolymers has been studied by both infrared and mechanical methods. Comparison is made between the weight‐averaged E(t) and H(τ) spectra of the parent copolymers and those of the mixed copolymers. The results indicate that the maximum contributions of bond‐interchange relaxation migrate to shorter times as the concentration of bonding groups increases.
Ionic bonding in butadiene copolymers. II. Stress relaxation
Authors: Otocka E. P. , Eirich F. R.
Published: April 2003

The mechanical lability of quadrupolar links in cationic and anionic polyelectrolytes and of ion‐pair links in mixed polyelectrolytes is investigated in terms of deviations from the WLF viscoelastic theory. The behavior of E(t), log AT, and Evisc indicate that the quadrupolar links do not interchange below the second transition Tt* found in these materials. The blended polyelectrolytes exhibit low yields of the desired ion pair linking and have transitions characteristic of quadrupolar migration of the unreacted polyelectrolytes.
Anisotropy of viscoelastic transitions in oriented polyethylenes
Authors: Stachurski Z. H. , Ward I. M.
Published: April 2003

Measurements have been made of the anisotropy of viscoelastic behavior in cold‐drawn low‐density and high‐density polyethylene sheets. In the low‐density polymer the β transition was shown to be highly anisotropic, maximum losses corresponding to shear on planes containing the axis of drawing and on planes perpendicular to this axis. In high‐density polyethylene the α transition shows anisotropy.
Interactions between Co(III) and Ni(II) complex ions and polyelectrolytes
Authors: Crescenzi V. , Pispisa B.
Published: April 2003

An investigation has been carried out of the interaction of optically active tris(ethylenediamine)–Co(III) and of tris(o‐phenanthroline)–Ni(II) complex ions with different polyelectrolytes in dilute aqueous solution. Optical rotatory dispersion measurements reveal that binding of the Co(III) complex ions occurs with a noticeable degree of specificity which in addition to depending on the nature of the fixed charges is also affected by the chemical constitution of the polyelectrolytes chain backbones. The dependence of tris(ethylenediamine)–Co(III) optical activity on polyelectrolyte concentration also exhibits interesting features. Polarimetric measurements of the rate of racemization of tris(o‐phenanthroline)–Ni(II) ions in the presence of different polyelectrolytes lead to similar conclusions. Sodium dextran sulfate is shown to interact selectively with one of the antipodes of tris(phenanthroline)–Ni(II) complex.
Relation of the decay of free radicals in irradiated polyethylene to the molecular motion of the polymer and the configurations of the free radicals
Authors: Nara S. , Shimada S. , Kashiwabara H. , Sohma J.
Published: April 2003

Decay reactions of the free radicals produced in irradiated polyethylene (high‐density and low‐density materials) were examined in connection with the molecular motion of the matrix polymer. Three temperature regions, in which the free radicals decay very rapidly, at around 120, 200, and 250°K, were designated TA, TL, and TB, respectively. The decay of the free radicals at these temperatures had activation energies in high‐density polyethylene of 0.4 kcal/mole for TA, 9.4 kcal/mole for TL, and 18.4 kcal/mole for TB. In low‐density polyethylene these quantities were 0.7 kcal/mole for TA, 23.1 kcal/mole for TL, and 24.8 kcal/mole for TB. Comparison of time constants for the decay reactions and for molecular motion of the matrix polymer indicate that the decay in TA and TB is closely related to molecular motion in the amorphous regions of the polymer. The decay of the free radicals at TL in high‐density polyethylene is due to molecular motion associated with local mode relaxation at lamellar surfaces, while that of low‐density polyethylene is due to local mode relaxation in the completely amorphous region. Steric configurations of the free radicals which decay in the respective temperature regions were also investigated.
Infrared spectra of polymer solutions. I. Conformational stability of isotactic polymer chains in solution
Authors: Kobayashi Masamichi , Tsumura Katsusuke , Tadokoro Hiroyuki
Published: April 2003

The infrared spectra of isotactic polystyrene, polypropylene, and poly‐p‐chlorostyrene were measured in dilute solutions or gels at various temperatures ranging from room temperature to −100°C. For isotactic polystyrene and polypropylene, all the absorption bands characteristic of the helical conformation of the molecules increase in intensity with decreasing temperature, and show intensities at low temperature as strong as in the highly crystallized samples. This suggests that the molecules can assume very regular conformations even in solution. Similar temperature dependence of the spectra was observed for a homogeneous gel of isotactic poly‐p‐chlorostyrene, which is believed to be noncrystalline. These experimental facts lead to the conclusion that the stability of the TG type helical conformation of these isotactic polymers may be ascribed to the intramolecular forces within a molecule. The fact that these spectral changes are reversible has permitted a thermodynamic treatment of the conformational regularity in solution on the basis of the infrared data. The temperature dependence of the absorption intensities has been interpreted quantitatively by a simple statistical mechanical model, and the enthaply and the entropy differences between the helical and the random states of the monomeric residue in the molecular chain have been estimated.
Huggins constant k′ for flexible chain polymers
Authors: Sakai Tsukasa
Published: April 2003

The Huggins constant k′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k′[η]2c2 + …), is calculated. For polymers in the theta condition, k′ is estimated to be 0.5 < kθ′ ≤ 0.7. For good solvent systems, the Peterson‐Fixman theory of k′ has been modified; the equilibrium radial distribution function in the original theory is replaced with a parametric distribution for interpenetrating macromolecules in the shear force field. Comparison of the modified theory with experimental k′ for polystyrenes and poly(methyl methacrylates) of different molecular weights in various solvents shows good agreement. An empirical equation which correlates the Huggins constant k′ and the viscosity expansion factor αη for polymers has been found to coincide well with the modified theory.
Structure of gum arabic and its configuration in solution
Authors: Swenson Harold A. , Kaustinen Hilkka M. , Kaustinen Ola A. , Thompson Norman S.
Published: April 2003

Gum arabic was found to have an osmotic molecular weight of 250,000, in agreement with earlier determinations. A molecular weight of 365,000 was found by light scattering, somewhat higher than obtained earlier by sedimentation equilibrium analysis but lower than light‐scattering values reported by other investigators. The M̄w/Mn ratio, 1.46, is quite low in gum arabic. The angular dependence of light scattering exhibited the upward curvature to be expected of a spherical molecule and a radius of gyration of about 100 A. or less, as estimated from a Zimm plot. Fractionation of the original gum arabic was done by precipitation of a 0.5% solution in aqueous 0.5% NaCl with acetone. Comparison of the curves of viscosity versus molecular weight and the estimated radius of gyration shows that the hydrodynamic volume is less than that of branched dextran of similar molecular weight. The electroviscous effects for gum arabic in aqueous solution were shown by reduced viscosity curves at various acidities and in salt. The degree of dissociation was calculated for each pH level. The minimum intrinsic viscosity was found in 0.04N HCl where the degree of dissociation at pH 1.5 was found to be 0.049. When the acidity was increased, further reduction in viscosity was found to be negligible. Routine determination of the viscosity and molecular weight of the fractions was done in 0.35M NaCl at pH 10 to which 0.25% of the sodium salt of ethylenediaminetetraacetic acid was added as a sequestrant. The intrinsic viscosity in this solvent was nearly as low as in 0.04N HCl. Light‐scattering dissymmetries in water and in 0.35M NaCl plus EDTA at pH 10 were similar, 1.13 and 1.09, respectively, which showed that actual expansion of the macroion is not the cause of the large increase in viscosity of gum arabic when the ionic strength of the solvent is reduced. Periodate oxidation of the polymer confirmed the existence of a 1–3‐linked backbone of galactose. Subsequent treatment of the oxidized polymer with alkali reduced the osmotic molecular weight to 45,000 but failed to remove oxidized side branches. The oxidized polymer was fractionated by gel permeation chromatography and the intrinsie viscosity–molecular weight relation compared with relations for fractions of the unoxidized polymer and for other branched and crosslinked polymers.
Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. I. Single crystals
Authors: Williams T. , Blundell D. J. , Keller A. , Ward I. M.
Published: April 2003

This paper describes the application of gel permeation chromatography to the morphology of polymer single crystals. Various types of single crystals of polyethylene were etched with fuming nitric acid, and the molecular weight distributions of the degraded fragments determined. The crystal preparations studied were monolayer crystals grown from xylene solution at 85°C and multilayer crystals grown at 84°C and 70°C. In all cases peaks in the molecular weight distribution were observed corresponding to single and double transverses of the molecular chains through the lamellae. By using the chromatograph calibration described in a previous paper, the position of these peaks were compared and correlated with previous estimates of lamellar thickness from low‐angle x‐ray measurements. The relative positions of the peaks provide information regarding the nature of the fold surface. The results are found to be consistent with a model in which the majority of the molecules are tightly folded.
Gel permeation chromatographic studies of the degradation of polyethylene with fuming nitric acid. II. Bulk polyethylene
Authors: Williams T. , Keller A. , Ward I. M.
Published: April 2003

Preliminary results are reported on the use of gel permeation chromatography in morphological studies of bulk polymers and fibres. Several samples of bulk isotropic and drawn polyethylene were analyzed by gel permeation chromatography following nitric acid oxidation. In all cases suitable samples showed two peaks in the molecular weight distribution, suggesting a qualitative similarity with results for single crystals. It is concluded that the present data are consistent with chain folding in bulk polymers, both in the isotropic and oriented states, with a less degree of regularity than exists in single crystals.