Testing viscometric predictions of the internal viscosity model, using dilute viscous theta solutions

Abstract

A stress-symmetrized internal viscosity (I.V.) model for flexible polymer chains, proposed by Bazua and Williams, is scrutinized for its theoretical predictions of complex viscosityη ^* (ω) =η′ − iη″ and non-Newtonian viscosityη (τ), whereω is frequency andτ is shear stress. Parameters varied are the number of submolecules,N (i.e., molecular weightM = NM _s ); the hydrodynamic interaction,h ^*; andφ/f, whereφ andf are the I.V. and friction coefficients of the submolecule. Detailed examination is made of the eigenvaluesλ _p (N, h ^*) and how they can be estimated by various approximations, and property predictions are made for these approximations.

Comparisons are made with data from our preceding companion paper, representing intrinsic properties [η], [η′], [η″] in very viscous theta solutions, so that theoretical foundations of the model are fulfilled. It is found that [η′ (ω)] data can be predicted well, but that [η (τ)] data cannot be matched at highτ. The latter deficiency is attributed in part to unrealistic predictions of coil deformation in shear.