Multiresponsive macroporous semi-IPN composite hydrogels based on native or anionically modified potato starch.

Macroporous semi-interpenetrating polymer networks (semi-IPN) composite hydrogels were synthesized by cross-linking polymerization of acrylamide (AAm) with N,N'-methylenebisacrylamide (BAAm) in the presence of potato starch (PS) or an anionic polyelectrolyte derived from PS (PA), below the freezing point of the reaction solution (-18 °C). The composite cryogels have been further modified by the partial hydrolysis of the amide groups in poly(acrylamide) (PAAm) matrix, under alkaline conditions. The influence of the entrapped polymer on the properties of the composite gels, both before and after the hydrolysis, has been evaluated by the swelling kinetics, FT-IR spectroscopy, scanning electron microscopy, and external stimuli responsiveness. The potential of the anionic composite cryogels as intelligent hydrogels has been evaluated by the investigation of the deswelling/reswelling kinetics as a function of solvent nature, ionic strength, and environment pH. Cryogels with fast responsivity at variation of the external stimuli, which withstood repeated deswelling/reswelling cycles, have been obtained at a low cross-linker ratio (one mole BAAm for 80 moles of AAm) and a monomer concentration around 3 wt%.