The current book describes the chemical and physical behaviour of polymers and biopolymers that form highly associating structures in equilibrium solution. It summons the established results known of polymer complexes in solution, taking into account also the recent developments in biotechnology concerning this topic, in technological applications of polymer-protein interactions, in fluorescence and scattering techniques for the study of intra- and interpolymer association and in the study of ionomers in solution. The book covers the whole range from synthesis and fundamental aspects to applications and technology of associated polymers.