Surface Physics Of Liquid Crystal---Studies On The Effects Of The Interface Between LC And Solid

The research on physical characters and laws of interface between liquid crystals (LC) and solids is one hot point of current LC science. The anchoring effect is of great importance and thought as the basis for producing the LC devices. The influences of interface on the distribution of LC抯 director are usually reflected by interface free energy, namely, the anchoring energy, it is the basic formula of interface physics. In 1969, Rapin and papanlar proposed the anchoring energy formula. Through various experimental examinations for about thirty years, it has been modified. The first order modification of RP formula has been accepted extensively. We will study the physical effects of interface based on the first order modification of RP formula. It consists of three parts. 1 .We take the typical weak anchoring nematic LC (WANLC) cell as our study subject. The state of LC will experience two transitions when the magnetic field, whose direction is perpendicular to the plates, grows from zero. The first one takes place at the threshold point and named after the Freedericksz transition. The second one takes place at the saturation point. Both transitions are thought as the second order transition, that is, the change of the distribution of LC抯 director is continuous. By the calculations, we find sometimes the free energy is not the single value function of H. So we take the state parameters u ( or u? for the theoretical deduce and numerical calculations. We prove that it is possible the first order transition takes place at both the threshold point and saturation point, namely, the change of LC抯 director抯 distribution is discontinuous. In this paper, we presented the conditions of the first order transition. It抯 a important physical effect resulted from the first order modification of the RP formula that the first order transition can take place both at the threshold point and the saturation point. 2.We study the transition problems at both the threshold point and the saturation point of the WANLC cell under the influences of mutually vertical electric field and magnetic field. We also adopt the state parameters u ( or u?, and prove in principle that there also can exist the first order transition for the WANLC cell ?II ? under the mutually vertical elecb~ic field and magnetic field, namely, at the transition point, the value of u (or u? is not zero. The experiments found for strong anchoring NLC cell, the first order Freedericksz transition could take place under the mutually vertical electric field and magnetic field. Frisken and Palffy- Muhoray132?presented the conditions of the first order transition according to their theoretical work. In our paper, we will prove that if the anchoring intensity is large enough, our theoretical results turn to be the same as the one of Frisken and Palffy- Muhoray~?1, but there is a limitation to the first order transition for the strong anchoring cell, that is, the anchoring intensity A can抰 be very large, if not it wouldn抰 be the first order transition. These are important modifications to the theory of Frisken and Palffy-Muhoray. 3.It is another hot point to study the surface elastic free energy of LC. Assuming *0, we use the new variations to calculate and adopt the same methods of the above two chapters. We discuss the Freedericksz transition and come to the conclusions based on the assumption. We find the one which it抯 the seco...