INTRINSIC VISCOSITIES AND HUGGINS CONSTANT FOR ETHYLENE-PROPYLENE COPOLYMERS .1. EFFECT OF THE CORRELATIONS OF ORIENTATIONS IN THE PURE COMPONENTS OR IN THE SOLUTIONS ON THE SOLVENT QUALITY - VISCOSITIES IN LINEAR ALKANES AND 3 HIGHLY BRANCHED ALKANES

Intrinsic viscosities of three ethylene-propylene copolymers (33, 63, 75%, mole percent of ethylene) have been measured at 25°C in the series of linear alkanes and three branched alkanes 2, 2, 4-trimethylpentane, 2, 2, 4, 6, 6-pentamethylheptane, and 2, 2, 4, 4, 6, 8, 8-heptamethylnonane. Intrinsic viscosities are lower in branched alkanes than in linear alkanes for the 63 and 75% samples. The 33% sample is, on the contrary, more expanded in branched alkanes. Intrinsic viscosities depend very little on chain length for the branched alkanes for the three samples while they do in linear alkanes particularly for the 33% sample. Results are interpreted in terms of correlations of orientations between the alkanes and the ethylene sequences of the polymer. Correlations of orientations are possible without regard to the solvent chain length in the 75% sample which has a distribution of ethylene sequences of different lengths. On the other hand, the short ethylene sequences of the 33% sample correlate more easily with the short alkanes. The presence of a low free-volume component in the solution makes correlations of orientations possible even with short-chain molecules. The Huggins’ constant k’ seems to be higher for ethylene-rich copolymers in linear alkanes than in the other systems. Correlations of orientations between solvent and polymer increase the solvent quality. © 1979, American Chemical Society. All rights reserved.