Frederick Davey with Charles Rosenblatt

Surface Memory Effect for Liquid Crystals

Samples of liquid crystals are prepared by sandwiching two pieces of glass coated with a polymer, and inserting the liquid crystals in between. The polymers act to orient the liquid crystal molecules relative to the glass surface, however not all angles of rotation are necessarily fixed. When only one surface has an azimuthal constraint (using a rubbed polyimide, for example), and the other does not (as with the polymer polymethyl methacrylate) the imposed azimuthal orientation propagates to the surface without the constraint. A memory effect has been observed where, after some time, the secondary surface begins to constrain the liquid crystals in the same orientation as the primary surface. The causes and extents of this effect are unknown, and of primary interest in this project is the time it takes for the memory effect to be noticeable. Analysis of the effect will be done by aligning the liquid crystal in the bulk by an external electric field. The resulting orientation distribution through the cell can be determined by analyzing the intensity and polarization of a beam of light passing through the sample.