Order parameter evaluation of LC-polymer from the interferometric/refractometric data

The temperature dependence of refractive indices of homeotropically oriented comb-shaped polymer films was determined with the help of optical interference wedge method. For order parameter S(T) estimation from the refractometrical data the information about the temperature dependence of the polymer density is needed and it is also necessary to choose a local field model. Born expression for the molecular refraction invariant in the large temperature range was used for evaluation of the polymer density temperature dependence. The problem of local field effects was investigated in detail on the example of the low-molecular LC PAA. It was shown that for the relative order parameter S(T) estimation it was possible to use Haller's extrapolation method. In this case the results obtained for different local field models are close to one another and to the results obtained by other independent methods.