A generalized method to calculate diffusion rates in polydisperse systems. Application to miscible polymer pairs in the concentrated regime

A generalized method for calculating diffusion rates in polydisperse systems, valid in the concentrated regime, is outlined. In the formulation of the method the discrete variable that describes the molecular size, is replaced by a continuous variable in the same range. This replacement diminishes the number of degrees of freedom but keeping the essential physics of the original statement. The effects of monomeric friction coefficient, Flory-Huggins thermodynamic interaction parameter, individual species molecular weights, local molecular weights distribution and local Tg are consistently included in the model.