EFFECT OF DENATURANT AND POLYMER CONCENTRATION ON THE STRUCTURAL AND DYNAMICAL PROPERTIES OF AQUEOUS-SOLUTIONS OF POLY(N-ACETAMIDO ACRYLAMIDE)

Poly(N-acetamido acrylamide), PAAA, associates in aqueous solution. Dy namic and static light scattering and viscometry are employed to study this association in aqueous solution. The initial relaxation rate Ome ga(0) shows a q(3) dependence for PAAA in water (q is the magnitude of the scattering vector) even at concentrations as low as 0.03%. When t his polymer is dissolved in 2 M aqueous sodium thiocyanate, only a dif fusive (q(2)-dependent) relaxation mode is observed. The results of th e reduced viscosity of very dilute PAAA-water solutions suggest the fo rmation of clusters. Addition of sodium thiocyanate breaks up the clus ters. From static light scattering of PAAA-water solutions, it is foun d that the fractal dimension increases with increasing polymer concent ration. This indicates that the clusters become more compact at higher concentrations. This conjecture is supported by the viscosity results , where the reduced viscosity shows a large increase with concentratio n and passes through a well-pronounced maximum at c approximate to 0.0 5%.