Variable architecture polymeric materials have been developed covering interpolymeric complexes (IPC), graft copolymers and hydrogels constituted from natural and synthetic polymers which offer unique properties such as responsivity to temperature and/or pH, biodegradability, specificity, and biocompatibility. The interpolymeric complexes and hydrogels of PNIPAAm with alginate or chitosan behave as "smart" dual-responsive materials with transition temperature/pH values close to the physiological ones. This new class of interpolymeric complexes, graft copolymers and hydrogels can sense environmental changes in the physiological range and it has found application in drug delivery in which subtle pH/temperature differences are important. Drug delivery systems have been prepared and tested with good results. Kinetics of the swelling/loading and release of some drugs have been also evaluated. (C) 2009 Elsevier B. V. All rights reserved.