Synthesis And Characterization Of Semi-radialized Stimuli-Sensitive Hydrogel

As the main of thermo-sensitive polymeric materials,poly(N-isopropylacrylamide) (PNIPAM) undergoes rapidly volume changes in response to external temperature changes,which helps to perform targeting controlling delivery of drug.Whereas cross-linked hydrogels that were used mostly now respond to stimulus slower than linear hydrogels.While,the linear hydrogels are often restricted in the appllication due to their poor mechanical property. Therefore, in order to enhance the mechanical strength, thermo-sensitive poperties and drug-loading rate, the study on hydrogel of new type of structure throug modificating has had far-reaching significance.Based on the ideas above,we considerate the properties of traditional cross- linked hydrogels and inear hydrogels. In certain applications such as polymeric pump, a semi-radialized PNIPAM hydrogel,which is featured with both ends of linear PNIPAM chains being grafted onto semicircular and cross-linked PNIPAM chains,has been successfully prepared in a three-step process by a method of sequential synthesis. The fabricated P(NIPAM/NIPAM/NIPAM) is featured with both ends of linear PNIPAM chains being grafted onto semicircular and cross-linked PNIPAM chains The formation and structure properties of fabricated hydrogels, the effect of synthetic conditions and compositions on swelling, thermo-sensitive,crosslingker concentrations,the volume ratio of linear PNIPAM graft chains drug releasing propenies, and the mechanism of drug releasing were studied in this anicle.The formation and structure properties of PNIPAM gels with different synthetic temperatures and crosslingker concentrations were discussed. With the increasing of inear PNIPAM content,the swelling ratio of P(NIPAM/NIPAM/NIPAM) increased. At the same time,to prove the function of modification further,we replaced the cross-linked hydrogels to AAM. The effect of compositions on swelling,thermo-sensitive poperties of P(AAM/NIPAM/AAM) gels was focused. With the increasing of PAAM volume ratio,the LCST of P(AAM/NIPAM/AAM) gels increased;and the swelling ratio was strenthened with the increasing of linear PNIPAM graft polymer.The results show that the P(AAM/NIPAM/ AAM) graft polymers had great improvement in temperature-sensitivities compared with traditional PAAM.In this article,NaCl was used as the release drugs to investigate the controlled–release characteristics of P(NIPAM/NIPAM/NIPAM) and P(AAM/NIPAM/AAM) hydrogels. When environmental temperature is higher than LCST, the release rate is notablely larger than the rate in low environmental temperature. The results showed that these modificated hydrogels exhibited a well performance of thermo - sensitive controled-release,which was better than the traditional systems.