Nanosize-Induced Optically Isotropic Nematic Phase

We fabricated, in a polymer matrix, liquid crystal (LC) nanosized droplets with a correlation length xi of about 140 nm, which appear as an optically isotropic film. Differential scanning calorimetry (DSC) and light scattering measurements gave unambiguous evidences of an existence of nematic LC (NLC) order and fluctuation over a wide temperature range. The correlation length obtained by light scattering was consistent to the droplet size determined by a scanning electron microscope (SEM). The dynamic electro-optic (EO) response in such an isotropic NLC (IsoN) phase was found to be very fast, tens of mu s, in a confined geometry because of the local short-range nematic order in the IsoN phase. This type of EO effect is very attractive for next-generation LC displays and light waveguides because of (1) very dark view in the absence of a field, (2) very fast response being independent of temperature and applied electric field, (3) gray-scale display capability with a constant response time, and (4) unnecessity of any surface treatment. (C) 2011 The Japan Society of Applied Physics