Light-scattering study of thermoreversible aggregates from chemically modified PVCs: Outcomes for the gel state

Suspensions in diethyl oxalate (DEO) of aggregates of chemically modified p oly(vinyl chloride) (PVC), where a few chlorine atoms are replaced by benze nethiolate groups, have been studied by light scattering. The scattering pa ttern of the suspensions display a maximum whose intensity decreases while its position, q(m), remains virtually constant as a function of the degree of modification. Diluting further the suspensions with DEO entails a shift of q(max) toward lower q-values. As has been recently shown with normal PVC , this maximum arises from a liquidlike order between aggregates. At high d ilution the weight-average molecular weight and the z-average radius of gyr ation can be measured. It is found that both parameters decrease with incre asing the fraction of benzenethiolate groups, unlike what has been observed with another type of chemical modification (chlorine replaced by hydrogen) . These results are interpreted by considering fibrillar aggregates, and th e outcomes for the gel state, in particular for its elastic modulus, are di scussed.