The Quantum Chemical Study On Intermolecular Interaction Of Liquid Crystal And Surface Material

Liquid-crystal anchoring and aligment at a polymer surface are very important discussion in manufacturer of LCD,so the study of interaction between liquid crystal and polymer surface appears very necessary. Industrial applications of LCs in display device rely on the ability of the manufacturer to prepare a substrate surface that will promote a particular type of alignment. The traditional approach is simply to rub the surface of a polymer layer that has been applied to coat the substrate but the mechanism responsible for LC anchoring is still debated. There ate two popular point of view about the discussion. The earliest suggestion was that rubbing induced microgrooves in the surface ,and that with planar anchoring the topography favored alignment in the direction of the rubbing, since in that case no bending elastic energy would be introduced. According to another pint of view ,alignment is primarily due to molecular interaction between LC molecules and polymer chains, an effect that also usually makes the molecules line up in the rubbing direction.We use Gaussian03 to make a quantum chemical study on intermolecular interaction of 5cb and PVA.We choose 638 and 383 atoms to make two models .and optimized the model with the method of hartree-fock and sto-3g basement. Finally we have got the right model. Based on the optimized model we calculated the energy of 5cb and pva substrate. This energy give a support to the calculation of anchoring energy . Based on our conclusion ,the liquid-crystal director orientation appeared to be determined principally by the substrate chain orientation. Furthermore, the energy of the first model is 15.42kJ/mol about twice as much as the second one7.91kJ/mol. And this conclusion make a terrific fit to the truth that 5cb molecule has a strong dipole moment.