MOLECULAR TUBE MODELS OF BRANCHED POLYMER MELTS

We apply the tube model to a specific problem in polymer melt dynamics - the rheology of star polymers as an additive to a monodisperse linear matrix. We find that the tube dilation picture of constraint release may be applied to the relaxation of the star fraction. There are four qualitatively different cases depending on the relative concentrations and relaxation times of the two fractions. Terminal relaxation times and relaxation spectra are calculated for each case and compared with available experimental data. The existence of a modified Rouse relaxation such that G(t) approximately t-3/2 is argued.