Regulating the Chirality of the Superhelices Self-Assembled from Block Copolymer/Homopolymer Binary Systems by the Mixing Ratio of the Polymers

Abstract

Chirality control is one of the fundamental aspects of the research of chiral nanostructures. Currently, there are a few reports regarding the chirality variation of polymer nanostructures induced by ambient preparation conditions without changing the chiral sense of the polymer backbones. Herein, we report findings that the chirality of the superhelices self-assembled by a binary polymer system containing rodlike core-forming poly(γ-benzyl-L-glutamate) (PBLG) homopolymers and helical screw-forming poly(γ-benzyl-L-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) block copolymers can be varied by the mixture ratio of the polymers. It was found that the chirality of the PBLG-b-PEG/PBLG superhelices can change from right-handed to left-handed by decreasing the fraction of the block copolymers. In such a process, the PBLG backbone of polymers retains their right-handed helical conformation, while the arrangement of the pendant phenyl groups varies from a contracted left-handed form to an extended righthanded form, which leads to the chirality evolution behaviors of the superhelices. This work presents a novel route regulating the chirality of chiral nanostructures formed by chiral polymers and enriches our knowledge for chirality evolution behaviors from polymers to nanostructures.