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Polybutadienes made with six different catalyst systems were examined: (1) butyllithium, (2) “nickel-based”, (3) alfin, (4) “titanium-based”, (5) “cobalt-based”, and (6) free radical emulsion. The microstructure and macrostructure of the polybutadienes have been determined and are compared to the results published in the literature. These polybutadienes may be considered to be random terpolymers of cis, trans, and vinyl addition of butadiene. The glass transition temperature is specified by the vinyl content. The crystalline melting points of the high trans and also the high cis polybutadienes obey to a high measure Flory's equation for melting point depression of a random terpolymer. The molecular weights of the polybutadienes have been determined by light scattering and osmometry and the degree of long chain branching has been determined by the branching index, 〈g′〉. The macro-structural features of the linear polymers are confirmed by fractionation. However, the polydispersities calculated from fractionation data do not agree with those determined from light scattering and osmometry for the branched samples. The discrepancy is attributed to the method of characterization of the fractions. A distinction is made between molecular weight distribution and molecular size distribution.

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SYNOPSISIt was the objective of this paper to assess the applicability of the universal calibration method to aqueous GPC/SEC with nonionic and anionic polymers using the Viscotek differential viscosity detector. Three water-soluble polymers-polyacrylic acid, dextran, and polyethylene oxide-were chromatographed using four UltrahydrogelTM columns with 0.3 M NaCl and 0.1 M KHzP04 as the mobile phase adjusted to pH 7. Three distinct calibration curves were obtained. Upon addition of 10% methanol, a reasonably good universal calibration curve was obtained. However, quantitative analysis of the data exhibited about 5% deviation in average M,,, and M, for sodium polyacrylate as calculated from the single curve as opposed to about 40% when calculated from the composite curve. The applicability of three theoretical models for the universal calibration method was assessed, and a recommendation was made for future work.

SynopsisThe molecular weights and radii of gyration of Streptococcus salivarius levan fractions were obtained from light-scattering measurements iii water. Sedimentation coefficients and partial specific volumes of the fractions were also obtained. Double logarithmic plots of [q] versus and SO versus li?, yielded slopes having values of 0.17 and 0.62, respectively. The data and various calculated parameters show that levan from Streptococcus salivarius is highly branched and behaves hydrodynamically as a compact particle of spherical symmetry.