Accuracy of Nematic Visco-Elastic Constant Measurement Using Rayleigh Scattered Light

Abstract

We calculated the accuracy of the Frank elastic constants and Leslie's viscosity constants obtained by photon correlation spectroscopy of Rayleigh scattered light (PSRS) for 5CB. The visco-elastic ratio, Ki/ηi, can be determined with an error of less than 1%. The value of K2 obtained by using electric-field-applied PSRS (EFPSRS) is accurate to within 2.5%. Although K1/K2 can be obtained to within 2.5% by parameter fitting, the measurement error of K3/K2 was more than 20%. To improve the accuracy with which K3/K2 can be determined, we developed a new method that uses EFPSRS to obtain an absolute value of K3 directly. According to our simulation, this method reduced the measurement error of all of the elastic constants and the viscosity coefficients η splay, η twist, and η bend to less than 5%. We also calculated the measurement error of Leslie's viscosity constants. The value of µ2 can be determined with an error of less than 5%, while other viscosity constants have errors of more than 15%. Our error estimation can be applied to measurements of any other liquid crystals obtained by using PSRS.