Accelerated Phase Transition of Polybutene-1 in Polybutene-1/Polypropylene Blends Induced by Poly((butene-1)-<i>block</i>-propylene) Copolymers

Accelerating the form II to I phase transition of isotactic polybutene-1 (PB) and developing high-performance polyolefins are highly attractive for both academia and industry. Incorporating isotactic polypropylene (PP) into PB provides an effective approach to address these challenges. However, the incompatibility between PB and PP leads to phase separation within the blends. In this study, an asymmetric crystalline poly((butene-1)-block-propylene) diblock copolymer (PB-b-PP) with longer PP blocks was obtained from PB/PP alloy by using the temperature rising elution fractionation (TREF) technique. Various concentrations of PB-b-PP were introduced into an asymmetric PB/PP (80/20) blend with higher molecular weight PP. The PB-b-PP acted as an effective compatibilizer, significantly promoting the nucleation of PB form II and form I while accelerating the form II to I phase transition, with an optimal concentration of 2.5 wt %. The interfacial stress generated by the crystallization of two blocks in PB-b-PP, which spanned the interface between PP and PB phases, was transmitted via intercrystalline links and relieved by driving the nucleation of PB form I, thus accelerating the form II to I phase transition. This study aims to elucidate the form II to I phase transition mechanism, provide strategies to accelerate this phase transition, and support the development of high-performance PB-based materials.