Dynamic dilution, constraint-release, and star-linear blends

The dynamic dilution theory of stress relaxation, quantitative for star pol ymer melts, cannot be directly applied to star-linear blends. The linear ch ains on their reptation time scale tau(d) release constraints on the star a rms, resulting in constraint-release Rouse motion for the star arms not des cribed by dynamic dilution. We present a microscopic theory without adjusta ble parameters for stress relaxation in such blends, which is in excellent agreement with dynamic rheology data for the full range of blend fractions.