Control of Nanostructural Dimension by Crystallization in a Double-Crystalline Syndiotactic Poly(4-methyl-1-pentene)-block-poly(l-lactide) Block Copolymer

The control of nanostructural dimension by crystallization-induced chain stretching was investigated in a novel double-crystalline block copolymer, syndiotactic poly(4-methyl-1-pentene)-block-poly(l-lactide) (sPMP–PLLA), featuring a lamellar phase. Because of the similar glass transition temperatures of sPMP and PLLA, their blocks could crystallize under soft confinement (i.e., a crystallization temperature higher than the glass transition temperatures of the constituent blocks) in sPMP–PLLA. With the strong segregation of sPMP–PLLA, the first-crystallized sPMP block was templated by microphase separation to form confined crystalline sPMP lamellae within the microphase-separated lamellar texture. Most interestingly, the first-crystallized sPMP block may also induce significant stretching of the PLLA chains from the lamellar interface, resulting in the increase of microdomain thickness of the PLLA block. With the increase of crystallization temperature, this chain stretching may become more significant, re...