Amphiphilic random and random block terpolymers with PEG, octadecyl, and oleyl pendants for controlled crystallization and microphase separation

Abstract

Controlled crystallization and microphase separation of multi-component copolymers are one possibility to construct precise nanostructures in functional polymer materials. In this paper, we report the crystallization and sub-10 nm microphase separation of amphiphilic random and random block terpolymers in the solid state. By using living radical copolymerization, we designed A/B/C random terpolymers and A/C–B/C random block terpolymers, into which a hydrophobic and crystalline octadecyl group (A), a hydrophobic and amorphous oleyl group (B), and hydrophilic poly(ethylene glycol) (C) were randomly and/or site-selectively introduced as side chains. The crystallization and melting temperatures of A/B/C random terpolymers gradually decreased with increasing content of amorphous oleyl units. The random terpolymers with a relatively small amount of oleyl units induced microphase separation of the side chains to form lamellae with hydrophilic and hydrophobic alternating layers in a domain spacing of about 6 nm, while the lamellar structure was gradually disordered by increasing oleyl groups. In contrast, A/C–B/C random block terpolymers efficiently induced crystallization of the octadecyl groups even in the presence of random copolymer segments with amorphous oleyl units. The random block copolymers opened the possibility of controlling microphase separation from the side chains of the random copolymers and the main chains of the block copolymers.