Superhelices Self-Assembled from Polypeptide-Based Polymer Mixtures: Multistranded Features.

Abstract

Poly(γ-benzyl-l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) rod-coil block copolymers and poly(γ-benzyl-l-glutamate) (PBLG) homopolymers can cooperatively self-assemble into superhelical structures in aqueous solution. Herein, we discovered that the helices can have multiple strands with tunable characteristics. The strand number was dependent on the initial polymer concentration of the self-assembly, the self-assembly temperature, and the weight fraction of the block copolymers in the mixture. Higher initial polymer concentrations or lower weight fractions of the block copolymers induced the formation of helices with larger diameters and higher strand numbers, and helices prepared at higher temperatures had higher strand numbers. Based on an analysis of the correlation between the geometric parameters of the helices and the strand number, a possible mechanism for the formation of multistranded superhelices is suggested.