Architecture Effect on Network Phase Formation from Controlled Self-Assembly of High‑χ Block Copolymers

This work aims to examine the architecture effect on the self-assembly of high-χ block copolymers (BCPs), polystyrene-block-polydimethylsiloxane (PS-b-PDMS). Lamellae-forming diblock and star BCPs with three and six arms were synthesized for self-assembly. A variety of self-assembled phases, especially network phases, can be formed by tuning the solvent evaporation rate for solution casting using PS-selective solvents (referred to as controlled self-assembly). In contrast to diblocks with linear architecture, the formation of network phases from star BCPs can be easily acquired via controlled self-assembly. It is possible to enrich the topological features of the forming network phases, giving double gyroid and Frank-Kasper-like network phases, with alternating three- and four-strut nodes, as well as a double diamond phase due to the alleviation of packing frustration from network formation. As a result, the architecture effect on the phase behaviors of high-χ BCPs via controlled self-assembly gives easy access to acquire a variety of network phases.