REFRACTIVE-INDEXES, DENSITY AND ORDER PARAMETER OF SOME LIQUID-CRYSTALS

The temperature variation of the refractive indices (n//o,n//e) and density are reported for two liquid crystals. The order parameter is evaluated by both Vuks' and Neugebauer's approaches. The possible sources of error in evaluating the order parameter from refractive indices measurements have been discussed. The contradictory behavior of DELTA n and DELTA // chi during the nematic-smectic B phase transition of HBT has been explained on the basis of polydomain formation and the order parameter in the S//B phase is estimated. The order parameter of two liquid crystals, HBT and OBT, is also evaluated by NMR measurements, confirming the polydomain formation in the S//B phase of HBT.