Self-assembly of liquid-crystalline block copolymers in thin films: control of microdomain orientation

Block copolymer (BCP) lithography, as one of the most promising techniques for the next-generation integrated circuits, has been extensively investigated in recent years. Among the diverse types of BCPs, liquid-crystalline BCPs (LC-BCPs) formed by incorporating LC moieties into the BCPs have become increasingly attractive because of the tunable alignment of the LC chains. This review highlights the control of the microdomain orientation of PEO-b-PMA(Az) thin films via novel and convenient processing methods, including micropore extrusion and the introduction of polydimethylsiloxane (PDMS). Meanwhile, the mechanisms of the microdomain alignment transition are clarified and are closely related to the soft shearing field and the change in the block surface energy. Furthermore, some new perspectives for future research on the self-assembly of LC-BCP thin films are outlined from the point of view of material design, orientation control, and technological innovation. The facile control of the microdomain orientation in the liquid-crystalline block copolymer (LC-BCP) thin films has been realized by means of micropore extrusion and introducing polydimethylsiloxane (PDMS), instead of complicated processes or costly apparatus. In extrusion process, the alignment can be recovered via ultrasonicating the extruded BCP solution or as-placing upon long-time thermal annealing.