Multiblock Copolymers Based on Highly Crystalline Polyethylene and Soft Poly(ethylene‐co‐butadiene) Segments: Towards Polyolefin Thermoplastic Elastomers

Abstract Block copolymers based on polyethylene (PE) and ethylene butadiene rubber (EBR) were obtained by successive controlled coordinative chain transfer polymerization (CCTP) of a mixture of ethylene and butadiene (80/20) and pure ethylene. EBR‐ b ‐PE diblock copolymers were synthesized using the {Me 2 Si(C 13 H 8 ) 2 Nd(BH 4 ) 2 Li(THF)} 2 complex in combination with n‐butyl,n‐octyl magnesium (BOMAG) used as both the alkylating and chain transfer agent (CTA). Triblock and multiblock copolymers featuring highly semi‐crystalline PE hard segments and soft EBR segments were further obtained by the development of a bimetallic CTA, the pentanediyl‐1,5‐di(magnesium bromide) (PDMB). These new block copolymers undergo crystallization‐driven organization into lamellar structures and exhibit a variety of mechanical properties, including excellent extensibility and elastic recovery in the case of triblock and multiblock copolymers.