Photoalignment of Vertically Oriented Microphase Separated Lamellae in LC–LC Diblock Copolymer Thin Film

The microphase separation and photoalignment behavior of a diblock copolymer consisting of two kinds of side chain liquid crystalline (LC) polymers are investigated. Here, the mesogens of photoresponsive azobenzene and non‐photoresponsive cyanobiphenyl are introduced in the side chains. The azobenzene and cyanobiphenyl mesogens orient homeotropically and planarly, respectively, in a thin film state. The combination of these contrasting orienting properties leads to a formation of vertically oriented lamella in the microphase separation structure. Irradiation with linearly polarized light onto this polymer film induces a highly oriented microphase separation structure having regularly elongated stripe morphology with 30 nm periodicity. The nearly defect‐free morphology of this LC–LC diblock copolymer after the photoalignment is a distinct feature when compared with those of coil (amorphous)–LC diblock copolymer films possessing the same azobenzene side chain. The microphase separation structure of liquid crystalline (LC)–LC diblock copolymer with hometropic/planar contrasting orienting properties of mesogens leads to a formation of vertically oriented lamella. Irradiation with linearly polarized light onto this polymer film generates a highly oriented microphase separation structure having a regularly elongated stripe morphology.