Nanosegregated Chiral Materials with Self-Assembled Hierarchical Mesophases: Effect of Thermotropic and Photoinduced Polymorphism in Rodlike Molecules.

Supramolecular chirality in a binary mixture of achiral bent-core (BC) and achiral rodlike mesogens was observed. Three different nanosegregated mesophases were determined in the binary system, and meaningful changes in circular dichroism (CD) were detected near the phase-transition temperatures of the rodlike mesogens. The highest CD intensity in the binary system was noted in the nanosegregated mesophase, in which the BC mesogens were in the helical nanofilament (HNF) phase and the rodlike mesogens were in the smectic A phase. The supramolecular chirality in the binary mixture was attributed to the self-assembled hierarchical chiral superstructures. Based on the experimental results, plausible scenarios for the chiral superstructures of the rodlike molecules embedded in the HNF networks are suggested. In addition, a system comprising BC and rodlike molecules doped with a photoresponsive compound exhibited remarkable photoswitching of CD intensity. According to the isothermal photoinduced phase transition of the embedded molecules in BC molecular HNFs, the observed CD intensities can be dynamically and reversibly modulated. Such a material with easily controllable functionality is of considerable interest in the field of materials science.

Polymer Stabilization of Liquid-Crystal Blue Phase II toward Photonic Crystals.

The temperature ranges where a pure simple-cubic blue phase (BPII) emerges are quite narrow compared to the body-centered-cubic BP (BPI) such that the polymer stabilization of BPII is much more difficult. Hence, a polymer-stabilized BPII possessing a wide temperature range has been scarcely reported. Here, we fabricate a polymer-stabilized BPII over a temperature range of 50 °C including room temperature. The fabricated polymer-stabilized BPII is confirmed via polarized optical microscopy, Bragg reflection, and Kossel diagram observations. Furthermore, we demonstrate reflective BP liquid-crystal devices utilizing the reflectance-voltage performance as a potential application of the polymer-stabilized BPII. Our work demonstrates the possibility of practical application of the polymer-stabilized BPII to photonic crystals.