A study on mechanism of pretilt angle generation in nematic liquid crystal for rubbed polyimide surfaces

We have studied the effect of the polymer tilt angle for pretilt angle generation in nematic liquid crystal, 4-cyano-4-n-penthylbiphenyl (5CB) on rubbed polyimide (PI) surfaces. The polymer tilt angle was determined by measuring induced optical retardation produced in rubbed PI surfaces by rubbing. We suggest that the polymer tilt angle is not related directly to the pretilt angle on rubbed PI surfaces by rubbing. We proposed a microscopic model of pretilt angle generation on rubbed PI surfaces by rubbing. Finally, we conclude that the pretilt angle generation of 5CB strongly depends on the characterization of polymer materials and the micro-asymmetric triangular structure of the polymer on rubbed PI surfaces.