Synthesis Of Poly(N-isopropyl Acrylamide-b-Acrylamide-azobenzene)Copolymer By Raft Polymerization

In this thesis,poly(N-isopropylacrylamide)(PNIPAm),poly(acrylamide-azobenzene)(PAAAB)homopolymers and its block copolymer(PNIPAm-b-PAAAB)were synthesized via re,versible addition-fragmentation chain transfer(RAFT)polymerization,using N-isopropylacrylamide(NIPAm)and acrylamido-azobenzene(AAAB)as monomers,benzyl dithiobenzoate(BDTB)as a chain transfer agent.Firstly,BDTB was synthesized by substitution reaction of dithiobenzoic acid brominated magnesium salt and benzyl bromide in the presence of iodine.The used dithiobenzoic acid brominated magnesium salt was prepared by the reaction of carbon disulfide and Grignard reagent formed from the reaction of bromobenzene and magnesium powder using THF as solvent.The resulting BDTB was characterized by 1H-NMR,FT-IR,and elementary analysis.The effects of solvent,temperature,iodine,eluent and absorbent used in column separation on yield and purity of BDTB were investigated.The results showed that pure BDTB was obtained using THF as solvent and iodine as catalyst at 50oC,and with petroleum ether as eluent and silica gel G254 as adsorbent for column separation.The yield of BDTB was about 45%.Secondly,PAAAB was synthesized by RAFT polymerization of AAAB,using BDTB as a chain transfer agent and AIBN as initiator.The structure and photo-responsive behavior of PAAAB were determined by FT-IR,1H-NMR,GPC and UV.The effects of reaction temperature,initiator and chain transfer agent concentration on the polymerization of AAAB were investigated.The results showed that the kinetic curves of the polymerization reveal good linear relationship,and the molecular weight distributions(<1.3)were narrower at 70?;the control for the polymerization at 70? was better than 80?;the polymerization rate,molecular weight decresed with the chain transfer agent concentration increases.The effect of the change of chain transfer agent eoneentration for the polymerization was smaller than initiator concentration.PAAAB has good photoresponsive behavior,and the rate of photoinduced isomerization and the recovery after equilibrium is slowed down with the molecular weight increase.Thirdly,PNIPAm was synthesized by RAFT polymerization of NIPAm,using BDTB as a chain transfer agent and AIBN as initiator.The resulting PNIPAm was characterized by FT-IR,1H-NMR,and GPC.The effects of reaction temperature,initiator and chain transfer agent concentration on the polymerization of NIPAm were investigated.And PNIPAm-b-PAAAB was prepared by RAFT polymerization,using AAAB as monomer,PNIPAm having BDTB moieties as a macromolecular chain transfer agent and AIBN as initiator.The results showed that the kinetic curves of the polymerization of NIPAm reveal good linear relationship,and the molecular weight distributions were narrower;the control for the polymerization of NIPAm at 60? was better than 70?;the polymerization rate and molecular weight of PNIPAm decresed with the chain transfer agent concentration increases and with the initiator concentration decreses.The resulting PNIPAm-b-PAAAB was confirmed by FT-IR,1H NMR,and GPC.