Nanocomposites based on Smart Hydrogels

TUNINETTI, J; MOLINA M.A.; STRUMIA, M.; RIVAROLA C.R; BARBERO C.A.

Viña del Mar

Workshop; Frontiers in materials reserch III.; 2006

Hydrogels are macromolecules with tridimensional structure and high capacity of water absorption. The hydrogels are smart in the sense that change physical dimension upon external stimuli (e.g. pH, temperature, pressure, ionic force)1. Therefore, they can be used in sensors and actuators2. It is possible to modify the properties of hydrogels by: copolymerization3 and/or trough formation of nanocomposites or interpenetrated networks (IPN)4. In the present communication we describe the copolymerization of N-isopropylacrylamide (NIPAM, sensitive to temperature) and 2-acrylamide-N-methylpropanesulfónico acid (AMPS, hydrophilic). Hydrogels are produced with crosslinked copolymers of N-isopropylacrylamide (NIPAM, sensitive to temperature) and 2-acrylamide-N-methylpropanesulfónico acid (AMPS, hydrophilic). The presence of AMPS increase the swelling (up o 5000 %) and increases the transition temperature of poly(NIPAM) hydrogels. Polyaniline (PANI) could be interpenetrated inside the gels. The mechanical properties improve and the transition temperature is decreased. Additionally, the conductive nature of polyaniline could be used to drive the phase transition using microwave radiation. Another way of modifying the properties is also described. Functionalized acrylamides are synthesized by reaction of N-phenylacrylamide with diazounium ions. The modified monomers are homopolymerized into gels alone or as interpenetrated networks of poly(NIPAM) gels. In the last case, the transition temperature is clearly affected by the presence of the interpenetrated network.