Sum-frequency generation (SFG) vibrational spectroscopy and second-harmonic
generation (SHG) were used to probe rubbed polyimide (PI) surfaces and liq
uid crystal (LC) monolayers adsorbed on them. The results show that rubbing
preferentially aligns PI backbones along the rubbing direction, but has li
ttle effect on the side chain orientation at the surface. However, adsorpti
on of an LC monolayer well aligned by the rubbed PI surface can cause the s
ide chains to tilt towards the rubbing direction.