Study On Preparation And Properties Of Poly(N-vinylacetamide) Series Hydrogels

Thermosensitive poly(N-vinylacetamide-co-vinylacetate) (P(NVA-co-VAc)) hydrogels were prepared via free radical copolymerization of hydrophilic NVA with hydrophobic VAc. Then the linear polymer, poly(acrylic acid) (PAA) or poly(2-(N,N′-dimethylamino)ethyl methacrylate) (PDMAEMA), which has pH sensitivity was respectively introduced into P(NVA-co-VAc) hydrogel internal to produce temperature and pH sensitive PAA/(P(NVA-co-VAc) semi-IPN hydrogel and PDMAEMA/(P(NVA-co-VAc) semi-IPN hydrogel. The results show that the hydrogels have good thermosensitivity, pH sensitivity, swelling-shrinking reversibility and the drug loading and release properties, while the semi-IPN hydrogels have some salt sensitivity.The prepared three kinds of hydrogels with more NVA in feed swell faster and the swelling ratios of hydrogels gradually decreased with temperature increasing from 10 to 90℃. It was found that the hydrogels showed good swelling-shrinking reversibility under 10 and 60℃.The swelling ratio(SR) of the Semi-IPN hydrogels decreased with the introduction of PAA, but raised with the introduction of PDMAEMA. And the variations of the pores in the hydrogels which were got by scanning electron microscopy were consistent to the changes of SR. With the pH rising the PAA/(P(NVA-co-VAc) semi-IPN hydrogels got higher SR. But the PDMAEMA/(P(NVA-co-VAc) semi-IPN hydrogels swell in acidic medium and shrink in alkaline medium. Meanwhile, the Semi-IPN hydrogels similar showed good swelling-shrinking reversibility under pH=1.0 and pH=7.4.The adsorption amount of model drug, sodium salicylate(SS) was higher in the three kinds of hydrogels containing more NVA and DMAEMA units and less AA units. The release of model drug had the same tendency to the transform of SR.