Phase Transitions of Bicontinuous Cubic Liquid Crystalline Compounds Confined in Nanoscopic Pores

Abstract

1,2-bis(4'-n-alkoxybenzoyl)hydrazine (BABH-n, where n is the number of carbon atoms in the alkyl chain) and 4'-n-alkoxy-3'-nitrobiphenyl-4-carboxylic acid (ANBC-n) exhibit bicontinuous Cub liquid crystalline phases having three-dimensionally periodic structure. We studied phase transition temperatures, phase structures, and molecular mobilities of the both compounds, confined in cylindrical nanoporous glasses with different diameters (50, 100, 200, 500 and 1000 nm) using DSC, synchrotron-radiated XRD, and ESR, respectively. As a result, when the pore diameter was decreased, interestingly, the phase transition temperature from Im3m- to Ia3d-Cubic phases increased although melting and clearing points were reduced. We considered this is due to restricted thermal expansion of the liquid crystalline compounds in the nanopores.