Self-supporting liquid crystal composite

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 undergoes a transition from the isotropic to the nematic phase. 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 structure. Using time-resolved laser scanning confocal microscopy (LSCM) we image the dynamics of the network formation at single particle resolution, for the first time. In the isotropic phase the particles perform Brownian motion, whereas in the network they remain frozen in position. We observe a broad distribution of the size of the liquid crystal domains of up to similar to50 micrometers. Healing shows although the network breaks up clusters of particles remain. DSC measurements show that the particles do not change T-NI, suggesting that the particles do not alter the bulk properties of the liquid crystal. These observations provide unimportant step towards characterising the material properties of this novel composite.