Por defecto: 

It is presented a generalization of the Mori-Zwanzig formalism applied to the
dielectric relaxation spectrum in polymer blends and solutions. This generalization consists in using fractional derivatives to describe the dynamics of the dipolarmoment autocorrelation function. Real and imaginary parts of second-order memory functions related to the complex viscosity for the high cis-polyisoprene (PI) are calculated. This polymer exhibits normal dielectric relaxation modes (Stockmayer type-A). From this analysis, it is showed the existence of a maximum in the imaginary part of the second-order memory function, which is related to their corresponding complex rotational viscosity.