THE RELAXATION OF LINEAR FLEXIBLE POLYMERS WHICH ARE SLIGHTLY POLY DISPERSE

The relaxation of slightly poly-disperse linear flexible polymers has been expressed in a simplified blending rule which is presumed to be a weighted linear superposition of the relaxation spectra of mono-dispe rse components which constitute the blend. Discrete components are cha racterized by their molecular weight M(i), weight fraction w(i), and r elaxation time spectrum H-i(lambda). In contrast to broadly distribute d blends in which the small molecules mobilize the large ones and vice versa, we introduce the term ''slightly polydisperse'' for blends wit h molecular weight distributions narrow enough to have very little cha nge in the longest relaxation times of each molecular weight component . The properties of this blending rule are analyzed and dynamic data i s calculated for slightly poly-disperse polystyrene. As an application , the blending rule is used to determine the characteristic mono-dispe rse parameters (BSW parameters) of two materials, poly (vinyl methyl e ther) and polycarbonate, for which we could not determine their BSW pa rameters directly since they were not available in nearly monodisperse form. The proposed blending rule can only be applied to systems in wh ich all components are above the entanglement molecular weight, i.e. M (i) much greater than M(c).