Orientation control of two-dimensional (2D) colloidal
liquid crystals
in both microscopic and macroscopic scales holds massive promise for
improved multifield applications. In this respect, graphene oxide
(GO) is used as a platform substance for 2D carbon-based lyotropic
liquid crystal (LC) materials. Here, we design the directed alignment
of aqueous GO-LC dispersion confined in a rectangular capillary tube.
The isotropic GO dispersion is loaded into a horizontal capillary
and subsequently concentrated to the LC phase by slow water evaporation
at open ends of the tube. An obtained surprising result, GO layers
organize normal to the inner surfaces of the capillary with a highly
ordered orientation of the optic axis over tens of millimeters. Such
transverse orientation of GO layers originates from the meniscus region
and then moves toward the center, caused by the interfacial effect
and the sequential isotropic-to-nematic transition. This aligned mesomorphic
system is characterized via optical retardation,
nematic order parameter, absorption, and modified Cauchy’s
transmission equation about the dependency of both birefringence and
wavelength with concentration. Finally, the aligned GO-LC layers are
preserved in a polymer composite matrix by photopolymerizing the evaporation-aligned
GO/acrylamide-LC dispersion confined in a capillary. This composite
shows higher thermal stability than polyacrylamide until 500 °C
of about 6.1%. Our experimental findings provide efficient advantages
for controlling the orientation of GO-LC and 2D materials, beneficial
for diverse optical applications due to their directional ordering.