Entropy of Activation of Viscous Flow in Dilute Solutions of High Polymers

Abstract

IT has been previously shown^1,2 that the entropy of activation of viscous flow, ΔS, of dilute solutions of flexible chain high polymers decreases with increasing concentration c and molecular weight M of the polymer. In contrast, ΔS for dilute solutions of cellulose derivatives, the chains of which are stiffer and more extended in solution³, generally increases with increase of c and M (refs. 1, 2 and 4). An interpretation in terms of positive and negative contributions to ΔS was tentatively advanced². The positive contribution was assumed to be proportional to Q/T, where Q is the apparent activation energy of viscous flow of the solution and T the absolute temperature. The negative contribution was assumed to be not primarily dependent on Q and to result from synchronization between movements necessary for a successful unit act of flow⁵. The effects of variation in c and M on Q are relatively small for dilute solutions of flexible chain high polymers and it was suggested that the negative contribution was the greater. The marked increases in Q with increase of C or M, observed with dilute solutions of cellulose derivatives, led to the suggestion that in such cases increases in the positive contribution outweighed any increases in the negative one.