Nanoconfinement-induced orientation changes in liquid crystalline block co-oligomers

Abstract

Liquid crystalline block co-oligomers (LCBCOs) are a distinct class of hybrid materials that combine the long-range structural order of block copolymers with the inherent molecular alignment capabilities of liquid crystals. Nanoconfinement using anodic aluminum oxide (AAO) templates offers a versatile platform for directing their hierarchical organization. Herein, we systematically investigate the self-assembly behavior of azobenzene-functionalized LCBCOs under nanoconfinement by varying the pore diameter (D_pore) of AAO templates from 100 to 30 nm. Grazing incidence small-angle X-ray scattering analysis reveals that different smectic mesophases—such as bilayer, interdigitated, and monolayer structures—emerge as D_pore decreases. The reduction in D_pore also induces a reorientation of LCBCO smectic layers from perpendicular to parallel alignment with respect to the surface normal. We find that these structural transitions are coupled with confinement-induced reorientation of azobenzene mesogens, which is further influenced by surface anchoring effects. Our results underscore the profound impact of nanoconfinement on the self-assembly and molecular orientation of LCBCOs, offering a promising strategy for designing next-generation anisotropic soft materials and stimuli-responsive systems.