Study On The Synthesis And Micellar Behaviours Of PPEGMEMA-b-PDABA Block Copolymer

In this thesis,poly(dehydroabietic butyl acrylate)(PDABA)and its block copolymer poly[poly(ethylene glycol)methyl ether methylacrylate]-b-poly(dehydroabietic butyl acrylate)(PPEGMEMA-b-PDABA)were synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization,using poly(ethylene glycol)methyl ether methylacrylate(PEGMEMA)and dehydroabietic butyl acrylate(DABA)as monomers,cumyl dithiobenzoate(CDB)as chain transfer agent,azobisisobutyronitrile(AIBN)as initiator.The micelles of PPEGMEMA-b-PDABA were prepared by dialysis against water.The structure of the polymers and the micellar properties of block copolymers were characterized and examined.Firstly,dehydroabietic butyl acrylate(DABA)was synthesized by the acyl chlorination of dehydroabietic acid(DHA)and esterification reaction,successively.Poly(dehydroabietic butyl acrylate)(PDABA)was synthesized by RAFT polymerization,using DABA as monomer,CDB as chain transfer agent,AIBN as initiator and toluene as solvent.The effect of reaction time,temperature,concentration of initiator and chain transfer agent on the polymerization of DABA was investigated.The results showed that the kinetic plot for the RAFT polymerization reveals a good linear relationship;the molecular weight of PDABA increases linearly with DABA conversion,and the molecular weight distribution is narrower.The molecular weight of PDABA decreases,its distribution becomes narrower and the conversion of DABA reduces,when the rate of[CDB]/[AIBN]increases.Secondly,the PPEGMEMA having CDB segment at the chain both ends was synthesized by RAFT polymerization,using PEGMEMA as monomer,CDB as chain transfer agent(CTA),AfBN as initiator and toluene as solvent.Then,PPEGMEMA-b-PDABA was prepared by RAFT polymerization,with PPEGMEMA as macromolecular chain transfer agent and DABA as the second monomer.The results showed that the molecular weight of block copolymer increases with DABA conversion,the molecular weight distribution is narrower;and the molecular weight distribution becomes broader as the reaction time increases.The PPEGMEMA having CDB segment exhibits the good control effect for the RAFT polymerization of DABA.Finally,the micelles of PPEGMEMA-b-PDABA were prepared by dialysis method against water,using DMF as solvent.The particle size,morphology,and thermo-responsiveness of the micelles were determined by DLS and TEM.The results showed that the shapes of the micelles are spherical,and the diameter is about 90-120 nm;the sizes of micelles decrease with the increase of temperature,which indicated that PPEGMEMA-b-PDABA possesses significant thermo-responsiveness.