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