Research On The Synthesis And Application Of Amphiphilic Block Copolymers Via RAFT Polymerization

Reversible addition-fragmentation chain transfer polymerization(RAFT)is an efficient and versatile controlled/"living" radical polymerization process,which use thioester as chain transfer agent(CTA).Since the birth of RAFT polymerization,which has provides a new approach for the design and synthesis of copolymers,especially the block copolymers.In this thesis,two amphiphilic block copolymer with different structLures has been designed and synthesized via RAFT polymerization:polystyrene-b-poly(2,2,2-trifluoroethyl acrylate)-b-polystyrene(PS-PTFEA-PS)and poly(ethylene glycol)-b-poly(4-vinylpyridine)(PEG-b-P4VP).In addition,the application of obtained PS-PTFEA-PS and PEG-b-P4VP copolymers in the fabrication of ordered porous films,electrospun spheres,electrospun fibers and nano titanium dioxide(TiO2)were preliminarily researched.1.Firstly,as the initial chain transfer agent,S,S’-Bis(α,α’-dimethyl-α"-acetic acid)trithiocarbonate(CTA1)and S-1-Dodecyl-S’-(α,α"-dimethyl-α"-acetic acid)trithiocarbonate(CTA2)were used for the synthesis of macromolecular chain transfer agent polystyrene-CTA,(PS-CTA1)and poly(ethylene glycol)-CTA2(PEG-CTA2)via RAFT polymerization of styrene with CTA]and esterification of methoxy polyethylene glycol with CTA2,respectively.In addition,a series of well-defined amphiphilic block copolymers PS-PTFEA-PS(Mn=5000-11000g·mol-1,PDI=1.13-1.17)and PEG-b-P4VP(Mn=9800-21000g·mol-1,PDI= 1.14-1.57)were synthesized via RAFT polymerization with PS-CTA1 and PEG-CTA2,respectively.The molecular structure and component of obtained copolymers were characterized through 1H NMR,19H NMR,GPC,FT-IR and elemental analysis.2.The hydrophobic ordered porous films of PS-PTFEA-PS copolymers were successfully fabricated via static breath figure(BF)process.The effects of solvent,temperature,molecular weight,relative humidity and polymer concentration on the surface morphology of such film were investigated.In addition,hydrophobic microstructured spheres and fibers of such block copolymers were fabricated by electrospinning process.The morphology was observed by scanning electron microscopy(SEM).Furthermore,the hydrophobicity of such porous films,spheres,and fibers were characterized through water-droplet contact angles.The results indicated that the porous film showed a good hydrophobicity with the water-droplet contact angles of 129°,and the fibers showed higher hydrophobicity with the water-droplet contact angles of 142°.3.Microstructured spheres and fibers of PEG-b-P4VP block copolymers were successfully fabricated by electrospinning process.The effects of voltage and polymer concentration on the morphology of such spheres and fibers were investigated.In addition,the micellization behavior of PEG-b-P4VP in butanol/ether and methanol/ether was also investigated.Moreover,PEG-b-P4VP was employed as template to prepare nano TiO2.The morphology and size of micelle and nano TiO2 were characterized through SEM and DLS.