Viscosity/temperature relationships for dilute solutions of high polymers

Abstract

Values of Q and A in the expression η = Ae Q RT have been obtained for dilute solutions of polyisobutylene, polyvinyl acetate, polymethyl methacrylate, cellulose trinitrate and cellulose triacetate in representative solvents. The apparent activation energy of viscous flow Q is given by Q= Q o + K e Mc where Q 0 is the value for the solvent, M and c are the molecular weight and concentration of polymer and K e depends on polymer and solvent. Values of K e for the cellulose triesters are much larger than for the other polymers and it is suggested that this is due to their greater chain stiffness and extension. For the polymers with flexible chains A= A o + K a Mβc over a limited molecular weight range but with the cellulose triesters A= A o exp (- K a ′ Mλc where A 0 is the value for the solvent and K a, K′ a, α and β depend on polymer and solvent. Application of rate theory suggests that the entropy of activation of viscous flow decreases with increasing c and M for solutions of flexible chain polymers but that the reverse is true for solutions of stiff, extended cellulose derivative chains. Equations are derived relating the intrinsic viscosity to K e, K a or K′ a, α or β, M and T.