title: Block copolymers with a twist.
abstract: Chiral block copolymers (BCPs*) comprising chiral entities were designed to fabricate helical architectures (i.e., twisted morphologies) from self-assembly. A new helical phase (H*) with P622 symmetry was discovered in the self-assembly of poly(styrene)-b-poly(l-lactide) (PS-PLLA) BCPs*. Hexagonally packed, interdigitated PLLA helical microdomains in a PS matrix were directly visualized by electron tomography. The phase diagram of the PS-PLLA BCPs* was also established. Phase transitions from the H* phase to the stable cylinder and gyroid phases were found after long-time annealing, suggesting that the H* is a long-lived metastable phase. In contrast to racemic poly(styrene)-b-poly(d,l-lactide) BCPs, chiral interaction significantly enhances the incompatibility between achiral PS and chiral PLLA blocks in the PS-PLLA BCPs* and can be estimated through the determination of the interaction parameter.
authors.affiliation: Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan. rmho@mx.nthu.edu.tw
authors.forename: Rong-Ming
authors.initials: RM
authors.lastname: Ho
authors.forename: Yeo-Wan
authors.initials: YW
authors.lastname: Chiang
authors.forename: Chun-Ku
authors.initials: CK
authors.lastname: Chen
authors.forename: Hsin-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Akasaka
authors.forename: Edwin L
authors.initials: EL
authors.lastname: Thomas
authors.forename: Christian
authors.initials: C
authors.lastname: Burger
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Hsiao