【作者】 崔陇兰；

【导师】 古宏晨；

【作者基本信息】 上海交通大学 ， 材料学， 2008， 博士

【摘要】 磁性聚合物微球不仅具有聚合物微球在合成、制备方面的可调控性、形貌多样性,同时具有磁性微球在磁场下的快速磁响应性,因而在生物医学领域显示出强大的应用潜力。从文献调研来看,目前,磁性聚合物微球的复合结构可分为核-壳型、反核壳型、夹心型、弥散型和中空型等五种。其制备方法按照磁性/聚合物两种组分生成顺序的不同可分为三类,即①磁粒子和聚合物组合法、②磁性纳米粒子原位生成法、③单体聚合法。然而,根据生物分离、分子生物学、医学等应用研究的需要发现:微米磁球所包含的磁性组分可占有较大的体积分数,磁响应强,但是其表面积小,对生物分子的吸附效率低;反之,纳米磁球的比表面积大,但磁响应低。因而,制备亚微米级、强磁性、单分散性、表面功能化的磁性复合微球一直以来都是科研工作者追求的目标。本文从细乳液聚合方法入手,以制备亚微米级、强磁性、单分散性、表面功能化的磁性聚苯乙烯微球为目标,全文从以下几个方面进行了探索和研究:1.首先用共沉淀法制备油酸修饰的磁性Fe₃O₄纳米粒子,平均粒径12nm,XRD分析证明得到的四氧化铁为面心立方结构。将这样的磁性Fe₃O₄纳米粒子分散在辛烷中配成磁流体,得到磁流体的磁浓度最高达到90wt%。然后用一步细乳液聚合方法制备出粒径约100 nm、Fe₃O₄含量高达50 wt%的磁性Fe₃O₄/PS复合微球。磁性Fe₃O₄/PS复合微球的粒径随表面活性剂的用量和超声功率的变化而可调可控。2.在一步细乳液的聚合体系中,通过苯乙烯和丙烯酸共聚的方法制备得到平均粒径为41-163nm,表面羧基化密度为0.058-0.25mmol/g,Fe₃O₄含量达到78wt%、饱和磁化强度高达44.7emu/g且单分散性较好的磁性Fe₃O₄/P（St-AA）共聚复合微球。Fe₃O₄/P（St-AA）复合微球的表面Zeta电位在pH=2-10的范围内为负,具有很好的稳定性。当丙烯酸用量超过苯乙烯的10wt%后,Fe₃O₄/P（St-AA）复合微球表面羧基密度达到饱和,平均粒径随丙烯酸用量和表面活性剂用量的增加而减小,微球中Fe₃O₄含量随磁流体用量（磁流体浓度一定）的增加而提高。3.以细乳液的稳定机制和传统乳液聚合的成核机理为理论基础,首次将两种方法的优势结合起来,创新性地提出杂化乳液聚合方法,从而有效地制备出粒径在50²00 nm之间,单分散性好、Fe₃O₄含量高达80 wt%以上的磁性Fe₃O₄/PS复合微球,并详细地研究了聚合过程中各种因素对产物各项性能的影响情况。研究表明引发剂的种类对复合微球的形貌有很大的影响,油溶性引发剂导致复合微球内部的磁/PS两相组分发生相分离,水溶性引发剂则可得到磁粒子在内部均匀分散的磁性聚苯乙烯复合微球;磁细乳液的体积用量与复合微球的Fe₃O₄含量成正比;磁细乳液中表面活性剂的用量与复合微球的粒径成反比;单体细乳液中超疏水剂的存在抑制单体的快速扩散,可以增加引发阶段的时间、减缓聚合速率,保证复合产物的单分散性特征。4.通过调控高沸点超疏水剂（十六烷）的用量和引发剂的种类来引导和控制细乳液聚合过程中各组分的相分离,首次采用两步细乳液的方法制备出红细胞型、环型和月牙型磁性Fe₃O₄/PS复合微球。更多还原

【Abstract】 Magnetic polymer microspheres show significant potential application in bio-medical field due to diverse polymerization methods, various morphology and quickly response to external magnetic field. From investigation of literature thoroughly, magnetic polymer microspheres could be classified into five kinds of composite structures including core-shell structure, reverse core-shell structure, sandwich structure, inner-dispersed structure and hollow structure. Up to now, according the producing sequence of magnetic and polymer components, there are three synthesis routes to realize the above-mentioned five composite structures, which are （1） combination method of former-prepared magnetic nanoparticles and polymer, （2） in situ preparation of magnetic nanoparticles in the presence of polymer beads, （3） monomer polymerization method in the presence of magnetic nanoparticles. However, the preparation of magnetic polymer microspheres with uniform size distribution and high magnetization is always an existent issue left for further investigation, in that the simultaneous improvement of magnetic content and size distribution is quite a challenge.In this dissertation, based on the miniemulsion system, a novel hybrid emulsion polymerization was firstly developed in order to prepare monodisperse, high magnetite content polystyrene microspheres. With this aim in mind, we carried out the following research contents.1. By co-precipitation method, oleic acid modified magnetic Fe₃O₄ nanoparticles with magnetite content of 87.5 wt%, face-centered cubic structure and average size of 12nm were easily prepared. The as-synthesized Fe₃O₄ nanoparticles were dissolved into octane to form ferrofluid with the highest magnetite concentration up to 90 wt%. Then, one-step miniemulsion polymerization was used to synthesize Fe₃O₄/PS composite microspheres with size about 100nm and magnetite content of 50 wt%. The effect of surfactant amount and ultrasonic power was investigated.2. Carboxyl-functionalized magnetic polymer microspheres were synthesized by adding acrylic acid （AA） into one-step miniemulsion polymerization system. Fe₃O₄/P（St-AA） microspheres with size range of 41～163nm, magnetite content up to 78 wt% and surface carboxyl density of 0.058-0.25mmol/g were obtained. These kind of magnetic polymer microspheres are stable in the changed pH environment （pH=2～10）. It was proved that the surface carboxyl density reached to saturation density when the addition amount of AA was 10 wt% （relative to St）, the average size was decreased by increasing the amount of AA and surfactants, and magnetite content was controlled by changing ferrofluid amount.3. With the combination of stabilization principle in miniemulsion system and the initiation mechanism in emulsion polymerization, a hybrid emulsion polymerization was developed for synthesizing Fe₃O₄/polystyrene composite microspheres with monodispersity, size range of 50～200nm and high magnetite content over 80 wt%. The influence of various parameters on various aspects of the as-synthesized Fe₃O₄/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag-miniemulsion and St-macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution.4. Two-step miniemulsion polymerization was designed to prepare magnetic polystyrene with various morphology composite structure including spherical structure, red-cell structure, ring structure and crescent structure. The amount of hydrophobic agent （hexadecane） and kind of initiator have obvious effect on the microphase separation in polymerization process.更多还原