ABA-type triblock copolymers and AB-type star diblock copolymers with poly(2-adamantyl vinyl ether) [poly(2-AdVE)] hard outer segments and poly(n-butyl vinyl ether) [poly(NBVE)] soft inner segments were synthesized by sequential living cationic copolymerization. Although both the two polymer segments were composed solely of poly(vinyl ether) backbones and hydrocarbon side chains, they were segregated into microphase-separated structure, so that the block copolymers formed thermoplastic elastomers. Both the ABA-type triblock copolymers and the AB-type star diblock copolymers exhibited rubber elasticity over wide temperature range. For example, the ABA-type triblock copolymers showed rubber elasticity from about À53 C to about 165 C and the AB-type star diblock copolymer did from about À47 C to 183 C with a similar composition of poly(2-AdVE) and poly(NBVE) segments in the dynamic mechanical analysis. The AB-type star diblock copolymers exhibited higher tensile strength and elongation at break than the ABA-type triblock copolymers. The thermal decomposition temperatures of both the block copolymers were as high as 321-331 C, indicating their high thermal stability.

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The ABA-type triblock copolymers consisting of poly(2-adamantyl vinyl ether) [poly(2-AdVE)] as outer hard segments and poly(6-acetoxyhexyl vinyl ether) [poly(AcHVE)], poly(6-hydroxyhexyl vinyl ether) [poly(HHVE)], or poly(2-(2-methoxyethoxy)ethyl vinyl ether) [poly(MOEOVE)] as inner soft segments were synthesized by sequential living cationic polymerization. Despite the presence of polar functional groups such as ester, hydroxyl, and oxyethylene units in their soft segments, the block copolymers formed elastomeric films. The thermal and mechanical properties and morphology of the block copolymers showed that the two polymer segments of these triblock copolymers were segregated into microphaseseparated structure. Effect of the functional groups in the soft segments on gas permeability was investigated as one of the characteristics of the new functional thermoplastic elastomers composed solely of poly(vinyl ether) backbones. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 00, 000-000