Synthesis and Self-Assembly of Silicon-Containing Azobenzene Liquid Crystalline Block Copolymers
Lin Weng, Mingchao Ma, Chenxiao Yin, Zhi-Xiong Fei, Ke‐Ke Yang, Caroline A. Ross, Ling‐Ying Shi
Abstract
The synthesis and self-assembly of a high interaction parameter silicon-containing liquid crystalline block copolymer (Si-LCBCP) are reported, containing thermally and photo-responsive azobenzene mesogens in the side chains which undergo molecular structural transitions, influencing phase transitions and orientation in the block copolymer. A series of the azobenzene-containing Si-LCBCPs, poly{dimethylsiloxane- b -11-[4-(4-cyanophenylazo)phenoxy]undecane methacrylate}, were synthesized through atom transfer radical polymerization, and the bulk self-assembly as well as the influence of the liquid-crystalline (LC) phase transition of the LC block on the microphase-separated nanostructure of the BCPs is described. As the volume fraction of the PMAAzo block ( f PMAAzo ) changes from 41 to 71%, lamellar, double gyroid (GYR), orthorhombic Fddd network, hexagonally packed cylindrical (HEX), and body centered cubic nanostructures were obtained. When f PMAAzo = 55–57%, a thermally reversible HEX-GYR- Fddd phase transition induced by the temperature change and LC phase transition was observed. Bulk morphologies are compared with thin-film self-assembly, and pattern transfer into silica nanostructures is demonstrated.