Structure analysis of ethylene/1-octene copolymers synthesized from living coordination polymerization

A series of ethylene/1-octene random and block copolymer samples were synthesized via a living coordination polymerization catalyzed by bis[N-(3-methylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride/dMAO. The chain microstructures of the copolymers were elucidated by analytic TREF and DSC thermal fractionation techniques in this work. It was found that the living random copolymers possessed narrower intrachain composition distributions than those prepared from conventional metallocene catalysts. With the same short chain branching content, the melting temperature of living random copolymer was about 16°C lower than metallocene-catalyzed random copolymer. The living block copolymers were also studied in comparison with the olefin multiblock copolymer (OBC) produced from chain shuttling polymerization. The interchain composition distribution of OBC was found broader than living block copolymers. However, the crystal thickness distribution of OBC was narrower. The diblock copolymer had a bimodal distribution in the crystal thickness and the step triblock copolymer showed a trimodal distribution, in contrast to OBC’s single modal distribution.