丝状相液晶由表面相互作用产生的相变

导出双轴丝状相液晶在指向矢与易取向轴重合时的表面相互作用能.应用Ritz方法，对半无 界液晶体得出沿表面法向的双轴相(B_c)至沿表面某一轴的双轴相(B_a)的相变.随着表面锚泊强度双轴性部分的增大，B_a的产生机制逐渐由降低温度 转为表面锚泊，因此B_a相可出现在较高温度和较大温度范围内.在表面锚泊强度 单轴性部分α值的一定范围内，增大α值可使B_a在较高温度产生，但α值的进 一步增大则使液晶又从B_α返回B_c相. 关键词： 液晶 相变 表面能

SURFACE PHASE TRANSITION OF NEMATICS INDUCED BY SURFACE INTERACTION

Using Ritz method in obtaining the surface order parameters,we obtained a phase transition from B_c,a biaxial nematic along the film normal,to phase B _a,a biaxial phase along the axis in the film plane.The result shows t hat as the biaxial part of the anchoring strength increases,the mechanism of the occurrence of B_a changes from temperature decreasing to surface anch oring.Within a certain range of uniaxial anchoring strength α,increasing α wil l make B_a occur at a higher temperature while further increasing of α will make the liquid crystal reenter B_c from B_a.