Dynamics of Polymer Solutions. 4. Shear-Stress-Relaxation Experiments on Solutions of DNA from Bacteriophage T2

We have previously described a stress-relaxation viscoelastometer which applies very small shear stresses to dilute solutions of large polymer molecules. Here we present experimental results. We show that in the limit of zero applied shear stress, and zero concentration, the primary retardation time is equal to the primary stress-relaxation time. We show that various stress-relaxation parameters are more sensitive to smaller molecules in the solution than are strain-relaxation parameters. One stress-relaxation parameter, a dimensionless measure of the primary relaxation amplitude, is found to be sensitive to the heterogeneity of the distribution of molecular weights, even at nonzero shear stress and concentration.