Effect of molecular weight on the rheological behavior of thermotropic liquid-crystalline polymer

Using a cone-and-plate rheometer, the steady and oscillatory shear flow properties of the polymer [OPhCOOPh(SO 2 Ph)OCOPhO(CH 2 ) 10 ] n (M w = 33000-45000, M w /M n = 2, T n→i = 161-176°C) were measured in both the nematic and isotropic regions. It was found that (a) η 0 ∞ M 6.5 and negligible N 1 in the isotropic region and (b) η 0 ∞ M 6 and N 1 ∞ M 6.7 in the nematic region, where M is the molecular weight, η 0 the zero-shear viscosity and N 1 the first normal stress difference