Structural polymorphism in bent-core liquid crystals: from helical nanofilaments to heliconical-layered microcylinders with light-responsive properties

Abstract

We report the self-assembly behavior and light-responsive polymorphism of azobenzene-containing bent-core liquid crystal dimers exhibiting B4 crystal phases. By systematically varying the terminal alkyl chain length, the supramolecular morphology transitions from helical nanofilaments (HNFs) with negative Gaussian curvature to heliconical-layered microcylinders (HLµCs) exhibiting cylindrical curvature. Dimers with short terminal chains form exclusively tightly packed HNFs, while those with longer chains assemble into HLµCs with increased interlayer spacing, indicative of reduced molecular interdigitation. Furthermore, UV-induced photoisomerization of azobenzene moieties enables dynamic alignment control during self-assembly, selectively suppressing HLµC formation and promoting the emergence of vertically aligned HNFs with vivid reflection colors. This study offers fundamental insights into molecular design principles and photoalignment strategies for curvature-directed self-assembly.