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-P-m-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-P-6-n series with a six-methylene spacer exhibit consistent microphase separation with slightly disturbed yet ordered columnar structures. While for PEG-b-P-10-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. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2544-2553