【作者】 夏奡；

【导师】 汪长春；

【作者基本信息】 复旦大学 ， 高分子化学与物理， 2009， 博士

【摘要】 近些年来由于生物医学研究的快速发展及对相关材料要求的提高,带有环境响应性的多功能磁性复合微球越来越受到人们的关注。为了满足生物医学领域的对高磁响应性微球的需求,不仅需要研究如何制备高磁性能的磁性粒子,还需要研究如何将制备得到的磁性粒子作为磁性功能单元与聚合物、二氧化硅等不同基体材料相结合,用以制备具有高磁响应性的多功能的复合微球。基于以上需求背景,本文研究工作主要围绕着高磁响应性聚合物及二氧化硅复合微球的制备和表征展开。并研究了在四氧化三铁磁性粒子作为磁性功能单元与聚合物、二氧化硅等基体的复合过程中,四氧化三铁磁性粒子和基体材料之间的相互作用,从而控制复合微球中四氧化三铁磁性粒子的载入量和在复合微球中的位置分布,制备具有不同织组层次结构的磁性聚合物基、二氧化硅基的复合微球。论文中的主要工作成果有以下几个方面:1、制备了具有不同粒径、形貌和表面性质的四氧化三铁磁性粒子,为进一步制备高磁响应性复合微球提供了不同类型的磁性功能单元。在组内以前的工作和现有文献总结的基础上,选择不同的路线制备了各种不同粒径、形貌和表面性质的纳米级或亚微米级的四氧化三铁磁性粒子,初步摸索和研究了在不同制备路线中反应条件对生成四氧化三铁磁性粒子的粒径大小、粒径分布、形貌和磁学性能的影响。首先,通过化学共沉淀法制备了平均粒径约为15纳米的单层油酸改性的油溶性四氧化三铁磁性纳米粒子。其次,采用有机金属络合物高温分解法和种子生长法,制备得到了粒径分别为4纳米、6纳米、9纳米、12纳米和14纳米的单分散的油溶性四氧化三铁磁性纳米粒子。再次,通过氢氧化亚铁凝胶氧化法制备了微米级和亚微米级的不同粒径大小和形貌的四氧化三铁磁性粒子。进一步引入相对浓度梯度法,研究了反应物浓度的变化对四氧化三铁磁性粒子的影响,考察了在制备过程中氮气保护对最终制备的四氧化三铁磁性粒子的粒径大小和形貌的影响。最后,通过溶剂热法制备了近单分散的亚微米级四氧化三铁磁性粒子。2、研究了将单层油酸改性的四氧化三铁磁性（Fe₃O₄）纳米粒子作为微球的磁性功能单元制备高磁含量的聚合物基微球的方法。利用聚合物基体对磁性纳米粒子的选择效应,结合乳液聚合方法,制备了具有不同组织层次结构的磁性聚合物微球。首先,将化学共沉淀法制备的单层油酸改性的Fe₃O₄磁性纳米粒子作为复合微球的磁性功能单元制备高磁含量的Fe₃O₄/PMMA聚合物微球。通过改变反应过程中加入乳化剂、单体和单层油酸改性的Fe₃O₄磁性纳米粒子的量,制备了具有不同磁含量的Fe₃O₄/PMMA聚合物微球,并且复合微球中Fe₃O₄磁性纳米粒子最高载入量接近60%,与目前商用的磁性微球的30%的磁性粒子的载入量相比,有了很大的提高。其次,研究了在反应过程中单体聚合形成的聚合物基体对单层油酸改性的Fe₃O₄磁性纳米粒子的选择效应,通过在制备过程中采用不同类型的单体和改变单体的聚合顺序对所得磁性复合微球结构进行控制,制备了PMMA/Fe₃O₄、PSt@Fe₃O₄、PMMA/Fe₃O₄@PSt、PSt@PMMA/Fe₃O₄等不同结构的磁性聚合物微球。并应用热力学原理对反应过程中单体聚合形成的聚合物基体对Fe₃O₄磁性纳米粒子的选择效应进行了理论上的初步推导和解释。最后,在制备前面多种结构的磁性复合微球的分析和总结的基础上,应用聚合物基体对Fe₃O₄磁性纳米粒子的基体选择性效应的原理,进一步制备了具有Janus结构的磁性复合微球。将所得Janus结构的磁性聚合物微球进行一维自组装,利用磁性复合微球中Fe₃O₄磁性纳米粒子的磁学性质对磁性复合微球的一维自组装原理进行解释。3、采用二氧化硅作为Fe₃O₄磁性粒子的包覆材料,通过选择不同二氧化硅复合微球的制备路线,使用不同粒径和表面性质的Fe₃O₄磁性粒子作为复合微球的磁性功能单元制备了高磁响应性二氧化硅微球。研究了反应过程中二氧化硅微球及微粒的形成机理,制备了具有不同结构和形貌的Fe₃O₄/SiO₂复合微球及微粒。首先,使用单层油酸改性的四氧化三铁磁性粒子作为复合微球的磁性功能单元,将Stober方法和乳液制备方法相结合,通过控制反应过程中氨水加入量的不同,调控四氧化三铁纳米磁性粒子在复合微球中的位置分布,制备了多种形貌的磁性二氧化硅微球。其次,采用复乳化的方法,将溶有单层油酸改性的四氧化三铁粒子的正硅酸乙酯（TEOS）作为复乳液的油相,调节制备过程中的乳化条件,控制乳液在相反转过程中水加入的速度,制备了W/O/W结构的复乳液滴,加入氨水制备得到具有Fe₃O₄/SiO₂磁性壳层的微米级空心磁性微球。再次,使用单层油酸改性的四氧化三铁磁性粒子作为复合微球的磁性功能单元,采用硅酸钠为二氧化硅的前驱物,乙酸乙酯或乙酸丁酯为反应控制剂,CTAB为乳化剂,通过改变起始反应物的浓度,制备了茄形磁性微粒、磁性二氧化硅线和空心二氧化硅磁性微球。研究了乙酸乙酯或乙酸丁酯作为反应控制剂、CTAB的加入方式和浓度对磁性二氧化硅微球及微粒的形态演化过程的影响。最后,使用溶剂热法制备的近单分散亚微米的四氧化三铁磁性粒子作为磁性二氧化硅微球的磁性功能单元,制备了高磁性响应性的Fe₃O₄@SiO₂复合微球。通过对高磁性响应性的单核Fe₃O₄@SiO₂微球表面进行MPS改性引入双键,在水溶液中引发NIPAM进行沉淀聚合。并研究了反应过程中引发剂的用量,微球表面MPS改性对聚合反应的影响,制备了具有高磁性响应和温敏双重环境响应性Fe₃O₄@SiO₂@PNIPAM复合微球。更多还原

【Abstract】 Due to the rapid development in the field of biomedicine and their demands for new materials,people pay more attentions to the multifunctional magnetic microspheres with stimuli-responsive to the environments.For the requirements of biomedicine to the high-performance magnetic microspheres,it is not only necessary to explore the synthesis of the high-performance magnetite,but also to fabricate the multifunctional high-performance magnetic microspheres,such as preparation of polymer and silica composite microspheres,in which the magnetite particles serve as a magnetic block.Based on the foregoing reasons,the research interest of this thesis is focused on the preparation and characterization of high-performance magnetic composite microspheres with a polymeric or silica matrix.The interaction between magnetite particles and matrix in the fabrication of the composite microspheres was investigated.Several kinds of magnetic polymeric or silica microspheres with different hierarchical structures were prepared.The main conclusions in this thesis are listed as follows:（1） For the preparation of a magnetic unit of high-performance magnetic microspheres,different kinds of magnetite particles were synthesized with various diameter size,morphology and surface properties.Based on the recent references,we developed several strategies to synthesize the nano,sub-micro or micro magnetite particles with specific sizes,shapes and surface properties.The reaction parameters were investigated on the as-prepared iron oxide particles’nature,such as the particle size,the size dispersity,surface and magnetic property.At first,iron oxide nanoparticles with a 15 nm diameter and a monolayer oleic acid capping surface by chemical co-precipitation process were synthesized.Then mono-disperse iron oxide nanoparticles with 4nm,6nm,9nm,12nm and 14nm diameters were prepared by high-temperature decomposition and seeded growth method.Subsequently,micro and sub-micro iron oxide particles with different diameters and morphology were prepared by the oxidized ferrous hydroxide gels. Through control the ferrous concentration in the reaction solution and the atmosphere, the size and the morphology of magnetite particles were well manipulated.Finally, near monodispersed magnetite particles with sub-micro size were prepared by solvent-thermo process.（2） High-performance polymeric microspheres with high magnetic content were prepared using the monolayer oleic acid capping iron oxide nanoparticles as magnetic unit.The magnetic polymeric microspheres with different hierarchical structures were synthesized by emulsion polymerization based on the principle of selective effect on the magnetic nanoparticles in the polymer.At first,Fe₃O₄/PMMA microspheres with a high loading of monolayer oleic acid capping iron oxide nanoparticles were prepared.Changing the concentration of the surfactant,monomer,and magnetic micelles in the polymerization,a serious of Fe₃O₄/PMMA microspheres with various contents of magnetic nanoparticles was prepared,and the highest loading of magnetic nanoparticlese was near 60%in the composite microspheres.Then,the principle of selective effect on magnetic nanoparticles in the polymer matrix was studied.Controlling the kind of monomers and the feeding order of monomers in the polymerization,a serious of magnetic microspheres was prepared with different hierarchical structures,such as PMMA/ Fe₃O₄,PSt@Fe₃O₄,PMMA/Fe₃O₄@PSt,PSt@PMMA/Fe₃O₄.The principle of selective effect on magnetic nanoparticles in polymer matrix was discussed based on the thermodynamic theory.Finally,based on the foregoing work of preparation different kinds of hierarchical composite microspheres,Janus magnetic microspheres were synthesized,and the Janus magnetic microspheres could self-assemble in one dimension.The self-assembly phenomena of Janus magnetic microspheres can be explained by magnetic properties of composite microspheres.（3） Several synthesis strategies were developed to prepare the silica composite microspheres with high magnetic content,in which magnetite particles served as a magnetic unit.According to the Stober method and the emulsion technology,different kinds of magnetic silica microspheres were synthesized.In the preparation,we found that the position of magnetic particles in magnetic silica microspheres was determined by the concentration of ammonia.Using the multiple emulsion method,magnetic hollow microspheres with a Fe₃O₄/SiO₂ magnetic silica shell were synthesized by the hydrolyzation and condensation of TEOS.In this preparation,the TEOS was used as oil phase,in which magnetic nanoparticles with a monolayer oleic acid were dispersed,and a W/O/W multiple（water-in-oil-in-water） emulsion was prepared with control of the emulsion parameters and the feeding speed of the water in the phase inversion process.Furthermore,controlling the initial concentration of reaction agents, kinds of magnetic composite microsperes were prepared,such as egg-plant,line and hollow structures.In this preparation,Na₂SiO₃ is as silica precursor,ethyl acetate or butyl acetate as pH controller and CTAB as surfactant.The influence parameters,such as the kind of ester and the feeding way of CTAB,were investigated.Finally, high-performance magnetic silica microspheres were prepared,in which the near mono-disperse sub-micro iron oxide particles synthesized by the solvent-thermo process were used.Before encapsulation of the composite microspheres,double bond was grafted on the silica surface by a modification of MPS.The precipitation polymerization of NIPAM was initialized by KPS in water,and the concentration of the initiator and the monomer was studied,then dual-responsive high-performance magnetic microspheres were prepared with a Fe₃O₄@SiO₂@PNIPAM structure.更多还原