Self-supporting liquid crystal composite

摘要

Colloid-liquid crystal composites are a novel type of soft condensed matter, formed from dispersions of colloidal particles in liquid crystalline hosts. Here, we investigate the kinetics of network formation in mixtures of the thermotropic liquid crystal 5CB and nearly hard sphere colloids (polymethylmethacrylate particles), occurring as the liquid crystal moves from the isotropic to the nematic state. In the isotropic phase the particles (volume fraction < 0.2) are homogeneously distributed. While cooling through the isotropic-nematic phase transition the particles are expelled by the liquid crystal, forming a three dimensional network. Using time-resolved laser scanning confocal microscopy (LSCM) we image the dynamics of the network formation at single particle resolution. The particles perform Brownian motion in the isotropic phase, whereas in the network they remain frozen in position. We observe a broad distribution of the size of the liquid crystal domains, up to a few micrometers. DSC measurements show that the particles do not change the temperature of the phase transition, indicating that the particles do not alter the bulk properties of the liquid crystal.