Self-Assembly of Bent-Core Nematics in Nanopores

Bent-core nematic liquid crystals exhibit unique properties, including giant flexoelectricity and polar electro-optic responses, making them ideal for energy conversion and electro-optic applications. When confined in nanopores, they can stabilize chiral nanostructures, enhance polar order, and enable defect-driven switching -- offering potential in nanofluidics, sensing, and adaptive optics. Here we examine the thermotropic ordering of the bent-core dimer CB7CB confined in anodic aluminum oxide (AAO) and silica membranes with precisely engineered cylindrical nanochannels -- ranging from just a few nanometers to several hundred nanometers. These well-aligned nanochannels enable high-resolution polarimetry studies of optical anisotropy, revealing how geometric confinement affects molecular organization and phase behavior. Under weak confinement, CB7CB forms a layered heterophase structure, with nematic, splay-bent, and twist-bent heliconical phases likely arranged concentrically. As confinement increases, a Landau-de Gennes analysis shows that ordered phases are suppressed, leaving only a paranematic phase under strong spatial constraints. Remarkably, temperature-dependent changes in optical birefringence under confinement closely resemble those seen under applied electric fields, revealing a parallel between geometric and electro-optic effects. Overall, our work demonstrates how nanoconfinement allows one to systematically tailor the self-assembly and optical behavior of bent-core nematics, enabling novel functionalities in responsive and anisotropic materials.