Dimension control on self-assembly of a crystalline core-forming polypeptoid block copolymer: 1D nanofibers versus 2D nanosheets

Abstract

Crystallization-driven self-assembly (CDSA) offers an effective strategy for delicate control of the nanostructures of block copolymers. Herein, we report the solubility effect on the self-assembly of a poly(ethylene glycol)-b-poly(N-(2-phenylethyl)glycine) (PEG-b-PNPE) block copolymer with a crystalline core-forming polypeptoid in aqueous solution. The influences of temperature, sonication and the corona-chain length that governs the solubility were systematically investigated. We demonstrate that the balance between the crystallization and solubility of the polymer dominates the nanostructures. When the crystallization of the PNPE block is restricted, 1D nanofibers are exclusively present. Otherwise, a majority of 2D nanosheets induced by CDSA are observed. Additionally, the π–π interaction also plays a crucial role in the assembly process. A phase diagram of PEG-b-PNPE assemblies at various DPs of PEG and PNPE is further shown. The capability to assemble the polymers into nanostructures with different dimensions through a facile assembly process offers a convenient platform to access a wide range of new materials for many applications.