Molecular-Weight Dependence of Viscoelastic Properties of Polystyrene Solutions

Abstract

Experimental data are analyzed to determine the molecular‐weight dependence of viscosity and oscillatory flow birefringence of polystyrene solutions in a partially chlorinated diphenyl solvent. Results for polystyrenes in the molecular weight range from 10⁴ to 10⁶ are given for the steady‐flow intrinsic viscosity, the high‐ and low‐frequency limits of the complex coefficient of viscosity for oscillatory flow, and the frequency dependence of the oscillatory flow birefringence. These properties are compared with the results of the theory for the flexible noninteracting Gaussian chain model composed of a finite number of chain segments and including hydrodynamic interaction within the chain as well as internal viscosity. The intrinsic viscosity is independent of the internal viscosity while the viscosity and birefringence in oscillatory flow are dependent on all factors. The three experimental properties are sufficient to determine the values of the parameters of the theory after correction for finite concentration effects. Over the complete molecular weight range studied it is found that approximately the number of monomer units per segment of the model is 10, the length of the segment is 3.0×10⁻⁷ cm, the ratio of the internal viscosity coefficient to segmental friction factor is 2.0, and the segmental hydrodynamic interaction factor is 0.3. The character of the measured properties and the theoretical results are in agreement.