Thermoplastic elastomers of alloocimene and isobutylene triblock copolymers

Abstract

A novel triblock copolymer, having a center block of high molecular weight polyisobutylene (PIB) and alloocimene (allo) end-blocks, was synthesized and the mechanical properties characterized. The phase-separated morphology consists of tethered PIB, with the glassy allo domains functioning as reinforcing filler. Thus, at ambient temperature the dynamic modulus is larger than that of PIB homopolymer by about 40%, and there is pronounced reinforcement from the glassy domains. The triblock polymer exhibits thermoplastic elastomer behavior, consistent with the structure. For temperatures above the allo glass transition (71 °C), the material undergoes an order–disorder transition, which causes substantial softening; however, this lability of the mechanical response is largely reversible. Since the repeat units of polyisobutylene cannot be crosslinked, this new material offers a route to processible, PIB based networks.