Amplification of vibrational circular dichroism in chiral block copolymers driven by self-assembly

Herein, various self-assembled phases including double gyroid (DG), double diamond (DD) and helical (H*) phases could be obtained from the self-assembly of chiral block copolymers with equivalent volume fraction of chiral segment, giving building blocks with equal contribution of the optical activities for self-assembly. Interestingly, with comparable chiral segment fraction as evidenced by electronic circular dichroism (ECD), significant enhancement of vibrational circular dichroism (VCD) signals could be found in the chiral H* phase while the VCD signals in the achiral phases of DD and DG remain after microphase separation for ordering, reflecting that the VCD enhancement is attributed to the formation of hierarchical helices with preferential handedness; the observed behaviors are represented as VCD enhancement by self-assembly. This finding provides a new concept to boost optical activities in the applications of chiroptic from self-assembly.