Synthesis And Micellar Behavior Of Poly[Poly(Ethylene Glycol) Methyl Ether Methacryl Ate]-b-poly-(Acrylamide-azobenzene)

In this thesis,poly[poly(ethylene glycol)methyl ether methacrylate](PPEGMEMA)and its block copolymer poly[poly(ethylene glycol)methyl ether methacryl ate]-b-poly-(acrylamide-azobenzene)(PPEGMEMA-b-PAAAB)were synthesized via reversible addition-fragmentation chain transfer(RAFT)polymerization,using poly(ethylene glycol)methyl ether methacrylate(PEGMEMA)and acrylamido-azobenzene(AAAB)as monomers,cumyl dithiobenzoate(CDB)as a chain transfer agent,2,2'-azoisobutyronitrile(AIBN)as initiator.Then,the amphiphilic block copolymer,PPEGMEMA-b-PAAAB was assembled into micelles in water.The structures and micellar behavior of these polymers and micelles were characterized and tested.Firstly,CDB was synthesized by reaction of Grinard reagent with carbon disulfide and ?-methylstyrene,successively.PPEGMEMA was synthesized by RAFT polymerization of PEGMEMA,using CDB as RAFT agent,AIBN as initiator.The effects of reaction time,temperature,RAFT agent and initiator concentration on the polymerization were investigated.The structure and thermo-responsiveness of PPEGMEMA were characterized and tested by FT-IR,1H-NMR,GPC and UV-vis spectrophotometer equipped with digital temperature controller.The results showed that the conversion of PEGMEMA increases with polymerization time increased,and the kinetic curves of the polymerization of PPEGMEMA reveal good linear relationships;the molecular weight distribution was narrow;when the ratio of[CDB]to[AIBN]increased,the polymerization rate and molecular weight of PPEGMEMA were decreased and the molecular weight distribution becomes narrower.The thermo-responsive,water-soluble PPEGMEMA exhibited a lower critical solution temperature(LCST)in water,and the LCST decreased with the increasing molecular weight and concentration of the polymers.Secondly,the amphiphilic block copolymer PPEGMEMA-b-PAAAB was synthesized by RAFT polymerization of AAAB,using PPEGMEMA as macromolecular RAFT reagent,AJBN as initiator and DMF as solvent.The structure and photoresponsiveness of PPEGMEMA-b-PAAAB copolymer were characterized and tested by FT-IR,1H-NMR,GPC,and Uv-vis.The results showed that the molecular weight of PPEGMEMA-b-PAAAB increases with the increasing conversion of AAAB,the kinetic curves of the polymerization reveal good linear relationships,and the molecular weight distribution was narrow(PDI<1.3).PPEGMEMA-b-PAAAB exhibited good photoresponsive performance,the maximum absorbance increased with molecular weight,and the isomerization rate decreased with increasing molecular weight of PAAAB in the copolymer of PPEGMEMA-b-PAAAB.Thirdly,amphiphilic block copolymer PPEGMEMA-b-PAAAB was dissolved in DMF,and assembled into micelle by dialysis against deionized water.Laser nano particle sizer,transmission electron micrograph(TEM)and Uv-vis were used to determine the size,morphology,and photoresponsiveness of the micelles.The results showed that micelle forms spherical aggregates,and partical size increases with molecular weight increased and decreases with Uv-vis irridation.