An evolution operator ℳ n with n arbitrary, typical of several models, is analyzed. When n = 1, the operator characterizes the standard linear solid of viscoelasticity, whose properties are already established in previous papers. The fundamental solution ε n of ℳ n is explicitly obtained and it's estimated in terms of the fundamental solution ε 1 of ℳ 1 . So, whatever n may be, asymptotic properties and maximum theorems are achieved. These results are applied to the Rouse model and reptation model, which describe different aspects of polymer chains.