title: Semicrystalline thermoplastic elastomeric polyolefins: Advances through catalyst development and macromolecular design.
abstract: We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90% elastic recovery at strains of 100% or less. An isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene-block-regioirregular polypropylene-block-isotactic polypropylene pentablock copolymer was synthesized that also shows exceptional elastomeric properties. Notably, microphase separation is not necessary in the semicrystalline isotactic polypropylenes to achieve good mechanical performance, unlike commercial styrenic thermoplastic elastomers.
authors.affiliation: Mitsubishi Chemical Center for Advanced Materials and Department of Materials and Chemical Engineering, University of California, Santa Barbara, CA 93106, USA.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hotta
authors.forename: Eric
authors.initials: E
authors.lastname: Cochran
authors.forename: Janne
authors.initials: J
authors.lastname: Ruokolainen
authors.forename: Vikram
authors.initials: V
authors.lastname: Khanna
authors.forename: Glenn H
authors.initials: GH
authors.lastname: Fredrickson
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Kramer
authors.forename: Yong-Woo
authors.initials: YW
authors.lastname: Shin
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Shimizu
authors.forename: Anna E
authors.initials: AE
authors.lastname: Cherian
authors.forename: Phillip D
authors.initials: PD
authors.lastname: Hustad
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Rose
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Coates