Semi-IPN hydrogels based on alginate-Ca2+ network and PNIPAAm:: Hydrophilic, morphological and mechanical properties

In this study, the thermosensitivity of semi-IPN hydrogels based on alginate-Ca2+ network and having PNIPAAm entangled was characterized by swelling degree (Q), scanning electron microscopy (SEM) and mechanical properties [compressive stress (sigma), apparent cross-linking density (v(e)) and modulus of elasticity (E)]. The Q values change inversely to the v e ones. The concentrations of the alginate-Ca2+ cross-linking and of the PNIPAAm chains contribute to the v. parameter. Higher values of Q correlate to larger pores size in the hydrogel. Hydrogels richer in alginate and PNIPAAm were more rigid, highly resistant to deformation because of their higher compressive modulus of elasticity. This is more intense at temperatures above the LCST of PNIPAAm in water (32-35 degrees C). The control of thermosensitive properties by tailoring the alginate-Ca2+/PNIPAAm ratio and temperature allows the hydrogels studied in this paper to be applied as drug delivery devices and/or as substrate for cell growth.