Preparation And Characterization Of Thermosensitive Polymeric Micelles

To study on the preparation and characterization of thermosensitive polymeric micelles,in this paper,the block copolymers,which involve polystyrene(PS)and poly(N,N-diethylacrylamide)(PDEA)as well as the other segments,were synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization method. And the nanomicelles based on these copolymers were prepared.The thermo-responsive behavior of the micelles was modulated and the stability of the polymeric micelles was enhanced by crosslinking the shell of the micelles.The main results are summarized as follows:1.PS-b-PDEA was synthesized by RAFT polymerization of St and DEA monomers.The block copolymer self-assembled into polymeric nanomicelles with uniform diameter.The micelles were thermodynamically stable in aqueous media with a low critical micelle concentration value.The micelles underwent a reversible phase transition in aqueous solution.The nanometer and thermosensibility enabled the micelles to be used as drug carriers with both passive and active targeting mechanism.2.PS-b-P(DEA-co-DMA)was successfully synthesized with RAFT method.By copolymerization of DEA with DMA,the lower critical solution temperature of the system was modulated so as to adapt well to the control release in human body. Prednisone acetate was loaded in the micelles.In vitro drug release from the drug-loaded micelles have a dramatically thermosensibility.To be used as drug carriers,they would accumulate at target sites and release drugs in a local hyperthemia method.3.PS-b-PtBA-b-P(DEA-co-DMA)was synthesized via RAFT polymerization, and PS-b-PAA-b-P(DEA-co-DMA)was obtained by hydrolysis method in acid aqueous solution.The three-layer polymeric micelles,which had a structure of PS core,PAA inner shell and P(DEA-co-DMA)outer shell,were prepared by dissolved the copolymer in anhydrous methanol.By crosslinking the inner shell of the micelles, the shell-crosslinked micelles was obtained,which could be advantageous for their use in the complicated environment of human body.