This volume focuses on the dynamical behaviour of low-molecular additives in solid polymer matrixes. It covers: types and models of molecular motion in condensed media; dependence of motional frequency on particle structure and size, temperature, volume and stress; and polymer properties and polymeric structures. Extensive analysis of common regularities of rotational and translational dynamics of molecules introduced into polymers are given. The book also includes experimental techniques for molecular mobility evaluation, and features detailed data on rotational dynamics of additives. It should be of interest to specialists in various fields of polymer physical chemistry and materials science.