<b>IPN hydrogels based on PNIPAAm and PVA-Ma networks: characterization through measure of LCST, swelling ratio and mechanical properties</b> - doi: 10.4025/actascitechnol.v34i2.15019

Abstract

IPN hydrogels based on chemically modified poly(vinyl alcohol) (or PVA-Ma), with different degrees of substitution (DS), and poly(N-isopropylacrylamide) (or PNIPAAm) were obtained and characterized through measures of LCST, swelling ratio and mechanical properties. Linear PVA-Ma with several DS were obtained through the chemical reaction of PVA with glycidyl methacrylate (GMA). The DS of various PVA-Ma were determined through ¹H NMR spectroscopy. Two steps were used for preparation the PVA-Ma/PNIPAAm membrane hydrogels. In the first step the PVA-Ma hydrogels (using PVA-Ma with different DS) were prepared by reaction of double bonds on PVA-Ma, using the persulfate/TEMED system. Using a photoreaction pathway in the second step, PNIPAAm network was prepared within the parent PVA-Ma network at different PVA-Ma/NIPAAm ratios. The studies show that degree of swelling ratio (SR) of PVA-Ma/PNIPAAm IPN hydrogels is dependent of temperature. The LCST for each IPN-hydrogel was determined by measuring the intensity of light transmitted through the hydrogel. The LCST of the IPN hydrogels ranged from 34.6 to 38.1^oC. The elastic modules of swollen IPN hydrogels increased from 25 to 35^oC but decreased by further warming to 45^oC. The LCST, swelling ratio and mechanical properties of PVA-Ma/PNIPAAm IPN hydrogels can be tailored by tuning the PVA-Ma/NIPAAm ratio.