PREPARATION OF FAST TEMPERATURE RESPONSIVE POROUS POLY(N-ISOPROPYLACRYLAMIDE) HYDROGELS USING SODIUM ALGINATE AS PORE-MAKING AGENT IN SODIUM CHLORIDE SOLUTIONS

Porous poly(N-isopropylacrylamide) (PNIPAAm) hydrogels were prepared using sodium alginate(SA) as pore-making agent in aqueous NaCl solutions. The porous structure of the PNIPAAm hydrogels was confirmed by SEM and SAXS, and the results showed that the pores in the hydrogels were interconnected and their pore sizes were increased with the NaCl concentrations used in the polymerization media. Accordingly, the deswelling rates of the porous hydrogels were enhanced with the NaCl concentrations. The water retention ratio of the porous PNIPAAm hydrogel prepared in 0.6 mol/L NaCl aqueous solution was less than 15% within 1 min when the equilibrium-swollen hydrogels at room temperature was 'transferred into the aqueous medium at 45 degrees C, and the deswelling equilibrium was achieved within 4 min. The porous structure of the PNIPAAm hydrogels may be caused by the micoparticles formed by coil-to-globule transition of sodium alginate chains in the NaCl solution.