| The smart gel is a cross-linked polymer which can occur a significant change when it undergoes physical and chemical stimuli such as temperature, pH, salt concentration, light, electrical field, chemical substances, it also can be called stimulative gels or sensitive gels. Such gels have a broad prospect in the chemical converter, switching memory devices, sensors, artificial muscles, chemical storage, molecular separation system, dimming materials, enzymes and controlled drug release and other high-tech fields.The responsive polymer containing polyethylene oxide(PEO) has been received extensive attention, because PEO itself has many excellent properties, especially, these excellent performance, such as hydrophilicity and biocompatibility, can be transferred to the new molecules when PEO coupled with other molecules. Another polymer, poly lactic acid(PLA), is hydrophobic and biodegradable, and its degradation products have no negative influences to the human body. Therefore, the amphiphilic polymers containing PEO and PLA chains have been studied extensively. In addition, the graft polymer has a faster response and the formation of the gel has a higher mechanical strength than the block polymer according to lots of references.In this dissertation, the triblock copolymers with PEO and PLLA segments were successfully synthesized by a combination of CROP and coupling reaction. At the same time, the graft copolymers, which main chain is chitosan(CS) and the side chains include PEO and PLLA were also synthesized by "click" and SET-NRC.1. Successfully designed and synthesized the amphiphilic triblock copolymer mPEO-b-PLLA-b-mPEO. First step, the linear mPEO was prepared by anionic ring-opening copolymerization of EO with2-(2-methoxyethoxy) ethoxide potassium as the small molecule initiators. Then, the obtained mPEO was used to initiate the ring-opening polymerization of L-LA as the macroinitiator, in the absence of Sn(Oct)2as the catalyst, and diblock copolymers wPEO-b-PLLA were successfully synthesized. Third step, the amphiphilic triblock copolymer mPEO-b-PLLA-b-mPEO was synthesized through the coupled reaction using gained diblock copolymer and MDI. The structure and molecular weight distribution of the triblock copolymer were investigated, the results show that the structure is defined and the molecular weight distribution is quite narrow. We also researched the gelation and drug release properties of copolymers which have different molecular weight and different concentration in water. The hydrophobic segment is more longer, the gel-sol transition temperature is more higher, and the drug release process is more slower.2. Further more, we successfully designed and synthesized the amphiphilic graft copolymer CS-g-(PEO-b-PLLA-b-mPEO). The preparation of the precursors is the first. The6-azide-N-phth-CS was prepared by three steps. The bromine-terminated mPEO-b-PLLA was prepared by mPEO-b-PLLA and2-bromoisobutyryl bromide, and the TEMPO-PEO-alkyne was prepared by DPMK as a initiator and HTEMPO and EO. Finally, the preparation of N-phth-CS-g-(PEO-b-PLLA-mPEO) is one-pot synthesis via combination of "click" and SET-NRC reactions. The final product and intermediates were characterized by1H NMR, FT-IR and ESR. They were proved that this strategy designed by us to prepare the graft copolymers with CS as main chain copolymer was successful. In comparison with the triblock, the graft polymer has more excellent performances, such as stimulative responsibility, gel mechanical strength and release performance. |
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