Nipam Homopolymer, Copolymer And Ipn Temperature-sensitive Gel Preparation And Properties

PNIPAm, P(NIPAm-co-AAm), PAAc/P(NIPAm-co-AAm) hydrogels were sythsized to investigate the relationship of tructure and properties of them. The formation and structure properties of the gels, the effect of synthetic conditions and compositions on swelling, thermo-sensitive, drug releasing properties, and the mechanism of drug releasing were studied in this article.Firstly, the formation and structure properties of PNIPAm gels with different synthetic temperatures, monomer concentrations and crosslingker concentrations were discussed. PNIPAm gels exist two different structures, homogeneous and inhomogeneous one. The former was transparent and elastic, and the latter was opaque. Structure inhomogeneity was mainly contributed to the phase-separation resulted by heat effect or the aggregation of certain reactant because of property difference with others. The effect of synthetic conditions on the structure and properties of PNIPAm gel was studied. With the increasing of polymerization temperature, the phase-separation and structure inhomogeneity was more fierce, leading to the decrease of the transmittance and elastic modulus, the increase of the swelling ratio. With the increasing of monomer or crosslinker concentration, the crosslinking was stronger, leading to the increase of and elastic modulus, the decrease of the swelling ratio.Secondly, the effect of compositions on swelling, thermo-sensitive properties of P(NIPAm-co-AAm) and PAAc/P(NIPAm-co-AAm) gels was focused. With the increasing of NIPAm content, the swelling ratio of P(NIPAm-co-AAm) increased and that of PAAc/P(NIPAm-co-AAm) decreased. P(NIPAm-co-AAm) gels had the property of shrinking thermosensitivity, while PAAc/P(NIPAm-co-AAm) had swelling one. With the increasing of AAm content, the LCST of P(NIPAm-co-AAm) gels increased, the thermosensitivity of them was weakened. While the thermosensitivity was strengthened with the increasing of AAm content.Thirdly, the drug loading and leasing ratio of P(NIPAm-co-AAm) and PAAc/P(NIPAm-co-AAm) gels was studied. The drug loading and leasing ratio of salicylic acid/dried gel system was dependent on hydrophobic interaction, while those of sodium salicylate acid/dried gel was on swelling ratio. With the increasing of NIPAm content, the salicylic acid loading ratio of P(NIPAm-co-AAm) andPAAc/P(NIPAm-co-AAm) inceased, and releasing ratio deceased. With the increasing of NIPAm content, the sodium salicylate loading and leasing ratio of P(NIPAm-co-AAm) gels increased, while those of PAAc/P(NIPAm-co-AAm) decreased.Lastly, the mechanism of drug releasing of P(NIPAm-co-AAm) and PAAc/P(NIPAm-co-AAm) gels was investigated. Salicylic acid/dried gel system releasing at swelling state was diffusion-controlled. The releasing of it at beginning stage was Fick -diffusion mode. Sodium salicylate/dried gel system releasing at swelling state was swelling-controlled. The releasing of it at beginning stage was zero-order mode..