Abstract
Visco-elastic properties of 5CB as a function of temperature in the nematic region are studied. Three Miesowicz viscosity coefficients ηa ηb and ηc and rotational viscosity γ1 are determined by dynamic light scattering (DLS) measurements. By assuming α3 ≅ 0, other Leslie viscosity coefficients are also calculated. Fitting our γ1 data to Osipov and Terentjev's theory, a coupling constant of 3.14kBTc is obtained, which is smaller than the mean field theory value. Temperature dependence of order parameter is obtained from refractive index measurement using Haller's method. To obtain accurate viscosity parameters from DLS, accurate values of elastic constants are required. Three different techniques are used to determine K11, K22 and K33, respectively: fitting the electric field dependence of capacitance to nematic continuum theory, ac electric field DLS and magnetic Freedericksz transition.