ORIENTATIONAL RELATIONSHIP AMONG POLYIMIDE ALIGNMENT LAYER, LIQUID-CRYSTAL MONOLAYER, AND BULK PRETILT ANGLE

We have determined the orientational distribution function (ODF) of si de chains of rubbed polyimide (PI) films and liquid crystal (LC) monol ayers on those films (PI & LC) by optical second-harmonic generation ( SHG). To separate the SHG signal of the LC monolayer from that of the (PI & LC) film, the phase difference between the SHG signals from PI a nd (PI & LC) was measured by an interference method. We found that the ODFs of PI and LC films are quite different. However, serious changes in these ODFs occur at the same rubbing strength, where the pretilt a ngle also shows a remarkable change. (C) 1996 American Institute of Ph ysics.