Temperature dependence of the pretilt angle generated on the rubbed surface of a side chain liquid crystalline polymer

While a wealth of data is available on the pretilt angle measurements at room temperature, there exist only a few reports on the temperature dependence of the pretilt angle. The present investigation is on the thermal variation of the pretilt angle of nematic liquid crystal molecules aligned on treated substrates. Glass substrates are coated with side chain-liquid crystalline polymer poly(4-cyanophenyl-4′-ethoxybenzoyloxy) acrylate (LCP100). An unusual temperature behavior is seen in way of two stable values for the pretilt angle (θ). As the temperature is increased θ changed from one stable value to another. On cooling the sample from the isotropic phase θ increased from zero to a second stable value and thereafter remained as a temperature invariant.