Preparation Of Mesoporous Titanium Dioxide Based On Self-assembly Of Polyethylene Glycol-b-Poly(R) Dodecyl Heptaacrylate Block Copolymer And Supercritical Fluid Technology

With the aggravation of environmental pollution,the decrease of petroleum,coal and natural gas resources and the increase of energy demand,storage technologies(such as dye-sensitized solar cells)and photocatalytic degradation of organic pollutant technology are highly valued.Titanium dioxide is an important semiconductor photocatalytic material.It has many advantages such as high photocatalytic degradation activity,corrosion resistance,chemical stability,non-toxicity and low price.It has important application value in environmental management and energy.In this thesis,mesoporous titania nanomaterials were prepared by using self-assembled structure of fluorinated block copolymer as template.(1)Synthesis and self-assembly of a fluorine-containing block copolymer polyethylene glycol monomethyl ether-b-poly(trifluoroheptyl methacrylate)(PEG-b-PDFMA).By the esterification reaction of RAFT reagent S-dodecyl-S'-bis(?,?"-methyl-?"-acetic acid)trithiocarbonate(DDMAT)and polyethylene glycol monomethyl ether(PEG),under the catalytic condition of cyclohexylcarbodiimide(DCC)/4-dimethylaminopyridine(DMAP)to obtain a macromolecular chain transfer agent;that is a macromolecular chain transfer agent,tetrahydrofuran(THF)is an organic solvent and azobisisobutyronitrile(AIBN)is used as initiator and DFMA is a fluoromonomer.A series of fluorinated block copolymers with controllable chain length and narrow molecular weight distribution were synthesized via reversible addition-fragmentation chain transfer(RAFT)dispersion polymerization;Self-assembly of PEG-b-PDFMA with different degrees of polymerization in a tetrahydrofuran/water system can form micelles with PEG as the shell and PDFMA as the core.(2)Preparation of mesoporous titania nanomaterials using fluoroblock copolymer PEG-b-PDFMA as a template.Micellar formed by PEG-b-PDFMA in tetrahydrofuran/water system as a template and sol-gel formed by the slow hydrolysis of titanium dioxide precursor tetrabutyl titanate(TBOT)in concentrated hydrochloric acid and acetic acid as inorganic component can co-assemble.Then PEG-b-PDFMA/titanium dioxide nanohybrid material was obtained by solvent evaporation induced self-assembly(EISA).After high temperature calcination,a mesoporous titanium dioxide nanomaterial with oblate oval cuboid structure was obtained.The effects of TBOT/PEG-b-PDFMA mass ratio,water addition,PEG-b-PDFMA/THF concentration,PEG-b-PDFMA polymerization degree and calcination temperature on the morphology of mesoporous titania nanomaterials were investigated.The optimal experimental conditions for the titanium dioxide nanoparticles with oblate oval cuboid structure were obtained:PEG-b-PDFMA has a polymerization degree of 40,TBOT/PEG-b-PDFMA has a mass ratio of 0.25/1,PEG-b-PDFMA/THF has a concentration of 10 mg/mL,and it was segmented at 40~oC and 70~oC,and calcined at 450~oC for 7 h under a nitrogen atmosphere.The prepared mesoporous titania nanomaterial has a specific surface area of 86.49 m~2/g,an average pore diameter of 6.2 nm,and a pore volume of 0.15 cm~3/g.(3)Based on the preparation of mesoporous titanium dioxide nanomaterials,we use fluorinated block copolymer PEG-b-PDFMA self-assembled micelles as a template,tetrabutyl titanate(TBOT)as precursor,supercritical carbon dioxide as a solvent and a desiccant to prepare the titanium dioxide nanomaterials,the effects of different temperatures and pressures on the morphology of the titanium dioxide nanomaterials were investigated.It was proved that the pressure only affects the size of the titanium dioxide particles,and the temperature causes a change in the morphology of the titanium dioxide nanomaterial.