Nematic–nematic phase separation from uniform nematic domain in polymer LC and low-molecular-weight LC mixture showing network lattice formation in pinning stage

Abstract

According to the well-defined phase diagram of a mixture of low-molecular-weight liquid crystal (LC) material and LC polymer, we investigated the LC/LC phase separation dynamics from the uniformly aligned nematic phase that was prepared by sandwiching it between rubbed cells with a thickness of 3 μm. Polymer compositions in the mixtures and decomposition temperatures varied from 28.3% to 34.4% and 14 to 21 °C, respectively. The phase separation proceeded in three stages in the following order; the early spinodal decomposition (SD) stage, later SD stage and pinning stage. In the final pinning stage, an ordered honeycomb network structure was formed wherein the low-molecular-weight LC-rich phases were accommodated within hollow microcells of the polymer LC-rich phase. The size of the network lattice was varied from 2 to 8 μm by varying the weight fraction of the mixtures and the decomposition temperature. Pinning lattice formation was discussed with respect to an interplay between orientational elasticity and anchoring effect on segregated domain boundaries, thus providing insights into nanoscopic self-organization in LC/LC segregation systems.