Study on the swelling kinetic of sodium alginate and poly(N-isopropylacrylamide) semi-interpenetrating(semi-IPN)hydrogel

The sodium alginate (SA)/poly (N-isopropylacrylamide) (PNIPAM) semi-interpenetrating (semi-IPN) hydrogel was prepared by incorporating SA into cross-linked PNIPAM to form a semi-IPN polymeric network. The properties of the semi-IPN hydrogel were characterized by DSC and SEM. The influences of the amount of SA in the senti-IPN hydrogel, pH and temperature on the swelling rates of these hydrogels have been thoroughly investigated. It is showed that at a temperature below the lower crifrical solution temperature ( LCST) and pH = 7.4 the swelling rate increases with increasing SA content in the semi-lPN hydrogel and relies on the relaxation rate of macromolecular chains in the hydrogel network. In addition, the effect of pH value on the swelling rate depends on temperature, while the effect of temperature on the swelling rate is also associated with pH value.