Ethylene Sequence Length of Ethylene-Propylene Random Copolymer and Crystalline Junction Size in Thermoreversible Gel

Abstract

Ethylene-propylene random copolymers (EP) in ethylcyclohexane or ethylbenzene convert to ther moreversible gels. Melting temperatures of the gels were measured as a function of polymer concentra tion and the crystalline junction size ζ, which is the number of consecutive ethylene units such as _??_CH₂CH₂_??_ζ, was estimated using the Takahashi theory. Moreover, weight-average length in number of consecutive ethylene units _??_(E)w was estimated from ¹³C-NMR measurements assuming the 1st-order Markov statistics and the value of _??_(E)w was compared with the junction size ζ formed in an EP gel. The unction size ζ decreased with increasing propylene content of an EP sample, and agreed approximately with the value of _??_(E)w, i.e., ζ_??__??_(E)w.