Preparation And Functional Properties Of Functionalized Double Network Hydrogels

This paper designed a water-soluble modified chitosan with both amidogen and carbon-carbon double bonds.N-isopropylacrylamide(NIPAM),glutaraldehyde(GA)and allylated chitosan(CSA)were used to prepare allylated chitosan/poly(N-isopropyl acrylamide)(CSA/PNIPAM)with Schiff base bond double network hydrogel.In addition,this paper also involved the molecular stent method and immersion of acrylamide(AM)to prepare a high strength polyvinyl alcohol/poly(2-acrylamido-2-methylpropane sulfonate)/polyacrylamide(PVA/PAMPS/PAM)double network hydrogel.The structure and properties of these hydrogels were studied.The main research contents and conclusions are summarized as follows:(1)Firstly,CSA soluble in water or acetic acid was obtained by using allyl bromide and nucleophilic substitution reaction,and the degree of allylation of CSA could be 14%by adjusting the ratio of the reagent.~1H NMR,FT-IR and XRD confirmed that the allyl group was successfully modified on chitosan.Initiated by a mild photoreaction,we used CSA with a carbon-carbon double bond to react with NIPAM.By FT-IR detection,we obtained the CSA/PNIPAM single network hydrogel,and the amidogen of CSA still existed after the reaction.(2)CSA/PNIPAM double network hydrogels were characterized by FT-IR,SEM and ~1H NMR.Diclofenac sodium(DCF)was used as a drug model to study the swelling properties and drug release process of hydrogels treated with different solutions.The results showed that the CSA/PNIPAM double network hydrogel with molecular switch.Under the condition of simulating intestinal environment(pH=7.4),the molecular switch of the hydrogel was closed,which provided some protection for the drug contained in the hydrogel and reduced the release of the drug under these conditions.While in the simulated gastric environment(pH=1.2),the molecular switch of the hydrogel was opened,and the release medium could change the release mechanism of the drug to improve the release efficiency.The cumulative release rate of diclofenac sodium could reach 70~80%,and the cumulative release time exceeded 800min.(3)High strength PVA/PAMPS/PAM double network hydrogel was characterized by FT-IR and XRD,and the mechanical properties and swelling properties of the double network hydrogels were studied.Mechanical tests showed that the construction of the molecular stent had a significant improvement on the mechanical properties of the hydrogel.After constructing the second network,the tensile strength of the hydrogel was significantly increased.High strength hydrogel with a large number of hydroxyl and sulfonic acid groups had an elongation of 109%and a tensile strength of 1.1MPa.In addition,the hydrogel could quickly return to its original shape after repeated bending,stretching and load.