Controlled synthesis and microstructure tuning of PEG-containing side-chain discotic liquid crystalline block copolymers via RAFT polymerization

Abstract

Liquid crystalline block copolymers (LCBCPs) are fascinating for their combining molecular level liquid crystalline orders and microphase separated multidomain morphologies. Here in this article, a series of PEG-containing side-chain discotic LCBCPs of PEG-b-Pm-n with variant spacer length m = 6, 10 and degree of polymerization (DP) of discotic LC block from n = 10 to 45, have been well-synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization. The RAFT process mediated by macromolecular chain transfer agent (macroCTA) shows remarkable monomer concentration dependence. The influence of the introduced PEG block on the nano-scale microphase-segregation and mesophase organization is closely related to the side-chain triphenylene (TP) discogens stacking mode dependent on the spacer length. Wherein, the PEG-b-P6-n series with a six-methylene spacer exhibit consistent microphase separation with slightly disturbed yet ordered columnar structures. While for PEG-b-P10-n series with a longer ten-methylene spacer, the columnar organization in the copolymers is even improved in contrast with the low order of randomly TP stacking in their corresponding homopolymers. This work offers a viable and inspiring pathway for controlled synthesis of block copolymers with bulky side groups, as well as enhances in-depth understanding of the hierarchical superstructure organization in discotic units involved complex block copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2544–2553