Swelling and Drug Releasing Properties of P(NIPAAm-co-AAm) Hydrogels and PAAc/P(NIPAAm-co-AAm) IPN Hydrogels

P(NIPAAm-co-AAm) and interpenetrating polymer network(IPN) hydrogels,PAAc/P(NIPAAm-co-AAm) with different compositions were prepared from acrylic acid(AAc),N-isopropylacrylamide(NIPAAm),and acrylamide(AAm) through free radical polymerization,in which N,N′-methylenebisacry-(lamide)(BIS) was used as a crosslinking agent.The swelling and drug releasing properties of these hydrogels with different thermosensitive properties were studied.The influence of the amount of AAm on the properties of these hydrogels was investigated.Experimental results revealed that these copolymer gels showed negative(temperature) sensitivity.When the molar ratio of AAm to NIPAm increased to 3∶1 from 1∶3,the effective crosslinking density of the copolymer gels increased to 3.071×10~(-6) mol/cm~3 from 2.518×10~(-6) mol/cm~3,and the equilibrium swelling ratio decreased to 15.36 from 18.65;thermosensitivity became weaker,and(sodium) salicylate releasing ratio of the copolymer gels reduced from 95.30% to 75.55%,and salicylic acid releasing ratio increased from 29.87% to 66.12%.However,IPN gels showed positive temperature sensitivity.With increasing the molar ratio of AAm to(NIPAm) from 1∶3 to 3∶1,the effective crosslinking density of IPN gels decreased from 31.06×10~(-6) mol/cm~3 to 26.92×10~(-6) mol/cm~3,and the equilibrium swelling ratio(increased) to 8.792 from 1.816;thermosensitivity of the IPN gels increased,and sodium salicylate releasing ratio(increased) from 41.56% to 59.65%,and salicylic acid(releasing) ratio also increased from 43.77% to 66.55%.