MOLECULAR-ORIENTATION AND SWITCHING BEHAVIOR IN ANTIFERROELECTRIC LIQUID-CRYSTALS STUDIED BY POLARIZED RAMAN-SCATTERING

The orientational distribution in SmA, the switching behavior in SmC, and the molecular orientation of SmCA have been investigated by mean s of polarized Raman scattering due to the C-C stretching of phenyl ri ngs in two antiferroelectric Liquid crystals. The scattered intensitie s, I-ZZ(omega) and I-YZ(omega), have been measured between crossed and parallel polars as a function of rotation angle, omega, of homogeneou sly aligned cells about their surface normal. The order parameters, <P -2> and <P-4>, and then the orientational distribution function in SmA were obtained by utilizing the method of information entropy. The ele ctric-field-induced reorientation was observed in the rotation angle d ependence: I-ZZ(omega)proportional to cos(4)(omega+/-theta), where the ta is the tilt angle of SmC. The characteristic rotation angle depend ence obtained in SMC(A) was described as I-ZZ(omega)proportional to{c os(4)(omega+theta)+cos(4)(omega-theta)}/2. This result supports the mo lecular orientation of SmCA so far proposed that the molecules in adj acent layers tilt in the opposite senses.