【作者】 汪洋；

【导师】 姜勇；

【作者基本信息】 东南大学 ， 化学工程与技术， 2021， 博士

【摘要】 近年来,磁性聚合物微球的制备引起了人们的广泛关注,虽然已经有各种各样的方法被应用到磁性聚合物微球的制备当中,但是想要制备出同时具有单分散性、超顺磁性、良好的均一性以及磁响应能力的磁性聚合物微球仍然具有较大难度。本文将围绕Fe₃O₄粒子与磁性聚合物微球的制备及性能研究开展工作,尝试采用一种新的、操作简单的表面引发聚合方法制备单分散、超顺磁性、均一性好、磁含量高的磁性聚合物微球,并研究其在生物医学、分离和催化等领域的性能表现。首先,通过共沉淀法制备柠檬酸钠改性的Fe₃O₄粒子,再利用溶胶凝胶法在Fe₃O₄粒子表面包覆一层Si O₂壳层,然后采用H₂O₂与Fe²⁺组成的氧化还原引发剂引发单体甲基丙烯酸羟乙酯（HEMA）聚合,制备Fe₃O₄@Si O₂-PHEMA复合材料并研究其对溶液中Cu²⁺的吸附情况。结果表明该复合材料其饱和磁化强度（简称磁强）为9.7 emu/g,能通过磁铁快速地从水中分离;研究表明该材料在弱酸性和弱碱性条件下对Cu²⁺的吸附能力均较强,这可能与PHEMA的酯键水解有关;该复合材料对Cu²⁺的吸附在20 min左右达到平衡,其最大吸附量为18.56mg/g。然后,受活性聚合表面引发制备单分散磁性聚合物微球的启发,结合Fe₃O₄粒子类过氧化物酶的性质,提出一种新的、操作简单的表面引发聚合方法,即Fe₃O₄粒子作为类芬顿反应的催化剂与H₂O₂组成氧化还原引发剂,通过Fe₃O₄粒子催化H₂O₂分解产生强氧化性的羟基自由基（OH^·）,从而引发单体在Fe₃O₄粒子表面进行聚合,制备出单分散性的磁性聚合物微球,并研究了反应时间、Fe₃O₄的浓度、苯乙烯（St）单体的加入量和H₂O₂的加入量对制备Fe₃O₄@聚苯乙烯（PS）微球的影响。结果表明该表面引发方法可用来制备不同尺寸、不同磁含量的单分散磁性聚合物微球。并用该方法制备的Fe₃O₄@PS微球负载Ag纳米粒子,得到树莓状的Fe₃O₄@PS@Ag微球,可用该微球催化还原有机染料。研究发现该微球能在较短的时间内还原90%以上的甲基蓝（MB,180 s）、罗丹明B（Rh B,50 s）和对硝基苯酚（4-NP,180 s）。接着,采用水热法制备大粒径的Fe₃O₄粒子,研究了Fe Cl₃·6H₂O、乙酸钠、聚丙烯酸（PAA）加入量和修饰剂种类对合成大粒径Fe₃O₄粒子的影响;比较了乳液自组装法、表面引发法和蒸馏沉淀聚合在制备磁性聚合物微球时的表现,结果表明蒸馏沉淀聚合在制备大尺寸的磁性微球时更有优势,制备出的微球具有更好的单分散性、均一性和更高的磁含量;然后采用蒸馏沉淀聚合制备600 nm左右的Fe₃O₄@聚甲基丙烯酸（PMAA）微球,该微球具有较高的磁含量（73%）和磁强（34.5 emu/g）,且均一性、单分散性较好;使用该微球吸附Ni²⁺,并将其还原成Ni纳米粒子,然后使其继续沉积生长制备出具有花状结构的Fe₃O₄@PMAA@Ni微球,该微球因为具有较高的表面Ni²⁺含量,可利用亲和吸附机理高效、选择性地纯化样品中的BHb,最大吸附量为2660 mg/g且循环性较好。最后,利用高温碱刻蚀法制备具有卵黄壳结构的Fe₃O₄@Ni Si O₃微球,使用聚乙烯吡咯烷酮（PVP）改善其在水溶液中的分散性。该微球具有花状表面结构和空腔,再利用其较大的比表面积均匀地原位负载大量的Ni纳米粒子,改善Ni纳米粒子的团聚,制备出Fe₃O₄@Ni Si O₃/Ni微球,并研究该微球在纯化BHb及催化4-NP还原两个领域的性能表现。结果表明该微球对BHb的最大吸附量为2822 mg/g,能在120 s左右将溶液的4-NP几乎全部还原（6 mg微球）且循环性和稳定性好;经过对Fe₃O₄@Ni Si O₃/Ni微球表面元素含量的研究得出结论:该微球能高效地纯化BHb和催化4-NP还原均得益于微球较大的比表面积和Ni纳米粒子的均匀大量负载。更多还原

【Abstract】 In recent years,the preparation of magnetic polymer microspheres has attracted extensive attention.Although a variety of methods have been applied to the preparation of magnetic polymer microspheres,it is still difficult to prepare magnetic polymer microspheres with monodispersity,superparamagnetism,good uniformity and magnetic response.In this thesis,the preparation and application performance of Fe₃O₄ and magnetic polymer microspheres were investigated.A new and simple surface initiated polymerization method was used to prepare the magnetic polymer microspheres.These microspheres was monodispersity,superparamagnetism,good homogeneity and high magnetic content.The performance and the application value of these microspheres were evaluated in biomedical,separation and catalysis.Firstly,Fe₃O₄ particles modified by sodium citrate were prepared by co-precipitation method.Then,a layer of Si O₂ shell was coated on the surface of Fe₃O₄ particles by sol-gel method.Fe₃O₄@Si O₂-PHEMA composites were obtained by the polymerization of HEMA monomer,which was initiated by the redox reaction of H₂O₂ and Fe²⁺.The saturation magnetization of the composites was 9.7 emu/g.The adsorption of Cu²⁺on the composites was studied.The composites had a high adsorption capacity for Cu²⁺under weak acidic and weak basic conditions,which might be related to the hydrolysis of the ester bond of PHEMA.The adsorption of Cu²⁺on the composite reached equilibrium in about 20 min,and the maximum adsorption capacity was 18.56 mg/g.Secondly,inspired by surface initiated method in living polymerization,a new and simple surface initiated polymerization method was proposed.It was based on the intrinsic peroxides-like properties of Fe₃O₄ particles.The polymerization was initiated by the highly reactive species OH^·which could be obtained by the decomposition of H₂O₂ under Fe₃O₄catalysis.The effects of reaction time,Fe₃O₄ concentration,the addition of styrene monomer and H₂O₂ on the preparation of Fe₃O₄@polystyrene（PS）microspheres were investigated.The results indicated that this method could be used to prepare monodisperse magnetic polymer microspheres with different sizes and magnetic contents.Then,Ag nanoparticles were loaded on the surface of Fe₃O₄@PS microspheres to obtain raspberry-like Fe₃O₄@PS@Ag microspheres.The microspheres could catalyze the reduction of methyl blue（MB）,rhodamine B（Rh B,50 s）and 4-nitrophenol（4-NP,180 s）in a short time（>90%）,which was MB for180 s,Rh B for 50s and 4-NP for 180 s respectively.Thirdly,Fe₃O₄ particles with large size were prepared by hydrothermal method.The effects of Fe Cl₃·6H₂O addition,sodium acetate addition,polyacrylic acid（PAA）addition and types of modifiers on the synthesis of Fe₃O₄ particles were studied.Magnetic polymer microspheres with large particle size were prepared by emulsion self-assembly,surface initiated method or distillation precipitation polymerization respectively.The results showed that the magnetic microspheres prepared by distillation precipitation polymerization had better monodispersity,homogeneity and higher magnetic content.Then,Fe₃O₄@polymethacrylic acid（PMAA）microspheres with about 600 nm in diameter were prepared by distillation precipitation polymerization.The microspheres had high magnetic content（73%）and magnetization（34.5 emu/g）.After that,Ni²⁺were adsorbed on the surface of the microspheres and it was reduced to be Ni nanoparticles.Ni nanoparticles were further deposited to obtain Fe₃O₄@PMAA@Ni with flower-like structure.Because of the high Ni²⁺content on the surface of the microspheres,Fe₃O₄@PMAA@Ni microspheres could be used to purify bovine hemoglobin（BHb）efficiently and selectively based on the affinity adsorption mechanism.The maximum adsorption capacity was 2660 mg/g,and the microspheres had good recyclability.Finally,Fe₃O₄@Ni SiO₃ microspheres with yolk-shell structure were prepared by alkaline etching method under high temperature.Polyvinylpyrrolidone（PVP）was used to improve the dispersivity of microspheres in aqueous solution.The microspheres had flower-like surface structure and a large cavity.Then,Ni nanoparticles were uniformly loaded on the flower-like surface structure of the microspheres.The performances of Fe₃O₄@Ni Si O₃/Ni microspheres in BHb purification and 4-NP reduction were studied.The results showed that the maximum adsorption capacity of BHb was 2822 mg/g,and4-NP could be almost completely reduced（6 mg microspheres）in 120 s with good recyclability and stability.The results indicated that the high efficiency of BHb purification and 4-NP reduction was due to the large specific surface area of the microspheres and the uniform loading of Ni nanoparticles.更多还原