Synthesis Of Temperature Responsive Polymers By Raft Polymerization And Their Application In Drug Control-Released Carrier

In recent years, reversible addition-fragmentation chain transfer polymerization (RAFT) has received much attention in the field of polymer synthesis due to its many advantages such as wide monomer applicability and mild reaction condition. This polymerization process is a kind of living control polymerization. The paper aims to the using control and activity characteristics of RAFT polymerization to synthesis single block and diblock temperature responsive drug carrier based on poly N-isopropyl acrylamide (PNIPAm). In this work, aspirin (APS) and urea was used as the model drug system to study on drug release under different temperature in vitro. Finally, we obtain a kind of sustained-release effect temperature responsive intelligent drug carriers. The paper consists of three parts and specific content as follows: 1.The polymer of poly(N-isopropylacrylamide)-b-chain transferagent(PNIPAm-CTA) was synthesized though RAFT polymerization using three dithiocarbonate two (a, a’-two methyl a-acetic acid) ester (BDTAC) as chain transfer agent and2,2-azobisisobutyronitrile(AIBN) as initiator. The polymer was keyed on the surface of chitosan to preparation poly N-isopropyl acrylamide grafted chitosan drug carrier (PNIPAm-g-CS). The characterization methods of FTIR,1HNMR and SEM were used to characterize the structure and properties of the polymer. APS was loaded on the polymer for imitating drug release experiment in vitro in PBS buffer solution (PH=6.8). The research shows that, The graft rate of PNIPAm-CTA is higher, sustained drug release effect is the most obvious; the release rate of APS at35℃was significantly higher than the release rate at29℃.2. The polymer (PNIPAm-CTA) was keyed on the surface of SiO2self-preparation for preparation drug carrier SiO2-PNIPAm.The characterization methods of FTIR,1HNMR, SEM and TEM were used to characterize the structure and properties of this polymer. In this chapter, aspirin (APS) and urea was used as the model drug system was loaded on this polymer. The release behavior was researched by ultraviolet and visible spectrophotometer (UV-VIS). The research shows that, The drug loading capacity is bigger, the drug release rate is high and drugs slow-release rate at29℃is greater than drug slow release rate at35℃.3. Xanthogenate was synthesized through reaction of soluble starch with carbon disulfide in alkaline solution. It was then reacted with methyl2-bromobutyrate to produce starch xanthate (SSX) as the chain transfer reagent in RAFT, AIBN as initiator, NIP Am and methyl methacrylate (MMA) as the monomers to prepare starch grafting block polymers with different percent grafting. The characterization methods of FTIR,1HNMR,SEM and UV-VIS were used to characterize the structure and properties of this polymer. The results prove that the lower critical solution temperature (LCST) of four polymers with different grafting rate are29.5℃、30.8℃、31.2℃、32.2℃because of the difference about grafted starch chain structure and molecular weight.This phenomenon can achieve the purpose of regulating the LCST of polymers. The drug loaded niosomes was prepared by Polymer PNIPAm-b-PMMA loaded APS in room temperature. The APS release behavior in different temperature were researched and the results show that the drug slow-release rate in29℃is lower than this conduct in35℃and the drug carrier showed temperature sensitive obviously.