Using Phase Separation as a

Play-Tool to Fabricate Liquid Crystal Optical Devices

Professor Satyendra Kumar

Department of Physics, Kent State University, Kent Ohio

And

Program Director, Condensed Matter Physics
Division of Materials Research, National Science Foundation

Phase separation of liquid crystal from its solution in a prepolymer initiated, for example, by UV exposure, was initially used to prepare polymer dispersed liquid crystal (PDLC) cells. PDLC cells are obtained when the rate of phase separation is faster than the diffusion of liquid crystal (LC) and prepolymer molecules. However, one can manipulate the rate of phase separation by controlling the brightness of UV and the diffusion of molecules via temperature to obtain different internal device architectures. In extreme cases, one obtains either columns or uniform layers of pure polymer adjacent to LC. Additionally, the use of masks during UV exposure can be used to design microscopic polymer structures to obtain various electro-optical devices. Fabrication of flexible plastic display cells, electrically controllable one- and two-dimensional diffraction gratings, and fly's eye lens with adjustable focal length will be discussed.