A STUDY OF HIGH PRETILT ANGLE GENERATION IN NEMATIC LIQUID-CRYSTAL (5CB) ON RUBBED POLYTHIOPHENE SURFACES WITH ALKYL CHAIN LENGTHS

High pretilt angles in nematic liquid crystals (NLC) have been generat ed on rubbed polythiophene (PTP) surfaces with different alkyl chain l engths. The pretilt angle of the NLC, 4-n-pentyl-4'-cyanobiphenyl (5CB ), was observed on unidirectionally rubbed PTP surfaces with alkyl cha ins with more than 9 carbon atoms. We obtained pretilt angle of 15-40 degrees on rubbed PTP surfaces with 10 carbon atoms in the alkyl chain . Also, the pretilt angles of 65-80 degrees of 5CB were obtained on ru bbed PTP surfaces with 11 and 12 carbon atoms in the alkyl chain. We s uggest that this high pretilt angle generation in 5CB is due to the su rface-excluded volume effect by the alkyl chain lengths between the LC s and the PTP surfaces. Finally, we conclude the odd-even effect on ru bbed PTP surfaces is clearly contributed to the pretilt angle generati on.