Self-aligning liquid crystals in polymer composite systems

Soft composite materials combined with a holographic photopolymerization process are used for realizing an innovative switchable periodic structure made of slices of almost pure polymer alternated with films of well aligned nematic liquid crystals named POLICRYPS. It exhibits negligible scattering losses, while the effect of the spatial modulation of the refractive index (from polymer to nematic liquid crystal) can be switched on and off by applying a low (few V/μm) electric field. The diffractive properties of the POLICRYPS structure are characterized in terms of cell thickness, impinging probe angle and wavelength revealing a strong correlation between the diffraction efficiency and all the above mentioned parameters. These results are very attractive for many applications such as switchable Bragg gratings for telecom devices, phase modulators, and displays. Other advantages of the technology include absence of an alignment layer, absence of haze, robust structure, and inexpensive manufacturing. In addition, no special alignment layers are required. This is a unique opportunity and a big advantage compared to conventional liquid crystal devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 158-162 Nematic liquid crystals spontaneously aligned in polymeric microchannels are used for realizing a nano/microcomposite switchable structure called POLICRYPS polymerliquid crystal polymer slides). It exhibits interesting optical and electo-optical properties such as uniform morphology, high diffraction efficiency, and low switching voltage. These features represent new opportunities for photonic applications based on POLICRYPS structures such as displays, active phase retarders, controllable optical routers, and diffractive filters. Copyright © 2013 Wiley Periodicals, Inc.