【作者】 高权星；

【导师】 童真；

【作者基本信息】 华南理工大学 ， 材料学， 2010， 博士

【摘要】 Pickering乳滴模板法制备有机/无机杂化的核壳微球越来越引起人们的关注,主要是因为该方法制备出的微球具有以无机粒子为壳层的超粒子结构,能够赋予微球独特的功能。胶体粒子在乳滴表面自组装形成有序的球面胶体壳,固定乳滴表面的胶体粒子来制备核壳结构的微胶囊。以胶体粒子为壳的微胶囊又称为胶体体微胶囊。本研究的主要目的是采用Pickering乳滴模板法制备有机/无机杂化超结构微球及其应用。我们根据所选择的不同性质和功能的核材料,采用Pickering乳滴模板法,对吸附在乳滴表面的胶体粒子用不同的固定方法制备具有不同结构和性能的胶体体微胶囊;并探索其在药物控释和微反应器领域的应用。使用不同性能、种类的纳米粒子制备多重Pickering乳液,考察其制备规律,了解影响其稳定性的因素;并利用基于多重Pickering乳液的聚合技术制备双纳米复合的超结构多核聚合物微球。本研究的主要内容和结果如下:1.采用疏水二氧化硅粒子稳定的正己烷包水的Pickering乳液体系,通过原位释放Ca²⁺使乳滴内海藻酸水溶液凝胶化制备了以海藻酸钙凝胶为核、SiO₂粒子为壳的胶体体微胶囊Alg/SiO₂。选用水难溶的蛋白质药物Insulin微晶作为模拟药物,装载到Alg/SiO₂微胶囊中,进行体外模拟释放,探索了胶体体微胶囊的控释性能。结果说明,海藻酸钙凝胶微球本身对Insulin有缓释作用,而SiO₂纳米粒子壳层的存在进一步减缓了Insulin的释放速度。分别采用一级动力学、Higuchi、Weibull及Hixson-Crowell立方根定律动力学方程拟合释放数据,发现其释放机理都可用Weibull方程来描述,都主要遵从Fick扩散。2.首次利用胶体体微胶囊作为酶催化微反应器。采用Pickering乳滴模板法,降温使乳滴内结冷胶水溶液凝胶化制备了以结冷胶凝胶为核、SiO₂粒子为壳的胶体体微胶囊Gellan/SiO₂。把生物大分子脲酶成功装载到Gellan/SiO₂微胶囊中,实现脲酶催化CaCO3晶体生成,模拟生物矿化过程,最终在结冷胶凝胶核表面生成了CaCO3/SiO₂复合壳层。以胶体体微胶囊为微反应器的模拟生物矿化过程制备了多重组分杂化的复合物。3.我们以正己烷为油相、异丙基丙烯酰胺水溶液为水相,通过SiO₂纳米粒子在界面的吸附形成稳定的w/o乳液。在不同温度下引发乳滴内的单体聚合,在反应温度高于聚异丙基丙烯酰胺的临界溶液温度（LCST）下制备出以PNIPAm/SiO₂为复合壳层的中空微胶囊;而在LCST之下的聚合得到以SiO₂粒子为壳、PNIPAm凝胶为核的实心微胶囊。以PNIPAm凝胶为核的微胶囊在去溶胀和温度升高时粒径变化明显;以PNIPAm/SiO₂为壳的中空微胶囊在去溶胀和温度升高时粒径变化不大,这是由于PNIPAm/SiO₂复合壳层限制了PNIPAm凝胶网络的收缩。实验结果证明,通过控制聚合温度能够对胶体体微胶囊的形态和性能进行调控。4.我们选取合适的亲水性粒子（亲水的三氧化二铁粒子,粘土粒子）和疏水性粒子（SiO₂粒子,疏水的三氧化二铁粒子）两两配对通过两步法制备了不同类型的多重Pickering乳液（w/o/w,o/w/o）。疏水性粒子为内界面层的稳定剂,亲水性粒子为外界面层的稳定剂,制备出能够长期保存的w/o/w乳液,而通过改变胶体粒子的加入次序,亲水性粒子作为内层界面的稳定剂,疏水性粒子作为外层界面的稳定剂,制备了稳定的o/w/o乳液。除了以粘土粒子作为外界面稳定剂的w/o/w乳液外,实验制备的多重Pickering乳液（w/o/w,o/w/o）能够放置超过3个月后仍然稳定没有破乳。引入功能性的PNIPAm纳米凝胶到多重Pickering乳液,制备以PNIPAm纳米凝胶吸附在外层界面的w/o/w多重Pickering乳液,并考察罗丹明B从该多重乳液中在不同环境下的释放行为。结果表明,PNIPAm纳米凝胶稳定的多重Pickering乳液具有温度和pH双重响应性,能够控制通过体系的温度或者pH值实现活性物质的快速释放。5.首次以多重Pickering乳液聚合技术制备了纳米复合超结构的多核聚合物微球。在粒子稳定的w/o/w乳液的油相和o/w/o乳液的水相中分别加入油溶性单体（苯乙烯）和水溶性单体（丙烯酰胺或者异丙基丙烯酰胺）,聚合反应得到多孔聚苯乙烯微球和多腔水凝胶微球。在纳米复合超结构多核聚合物微球中,一种纳米粒子主要在内核的壳层,另一种纳米粒子主要在整个微球的壳层,是三维有序的纳米复合;利用激光共聚焦显微镜、扫描电镜和FTIR等测试表征了该复合结构的存在。在多重Pickering乳液（w/o/w）中的内水相和内油相分别加入水溶性单体丙烯酰胺和油性单体苯乙烯,同时引发聚合制备具有复合多核结构的PS-PAm微球。PS-PAm微球内部存在多孔结构,孔与孔之间是并不相连的。胶体粒子在油水相同时反应的情况下仍能起到稳定乳液的作用,保证了聚合反应的顺利进行。并在干燥后的PS/PAm微球内部观察得到PAm凝胶以类似节点结构覆盖在内孔的表面。更多还原

【Abstract】 The organic/inorganic hybrid core-shell microspheres fabricated by the Pickering emulsion droplet template method have enjoyed great popularity. The microspheres obtained by this method have supracolloidal structures, which gives the microspheres special function. Colloid particles adsorb on the surface of the emulsion droplets and self-assemble into an ordering spherical solid shell. The colloid particles are fixed to prepare the core-shell microcapsules. The microcapsules with the shell of colloid particles are also called the colloidosomes. In this dissertation, we used the Pickering emulsion droplet template method to prepare the organic-inorganic hybrid core-shell microspheres. The different original materials for the core and the different method for fixing the colloid particles absorb onto the droplet have been chosen to obtain colloidosomes with different structures and property. Further, the application of the colloidosome for controlled release of drug and the biomimetic reactors can also be researched. Different kinds of nanoparticles were used to prepare the multiple Pickering emulsions. The prepare method and the effect on the stability of the emulsions were investigated. We also prepared dual nanocomposite multihollow polymer microspheres by multiple Pickering emulsion polymerization. The main contents and the results of the research are as following:1. Based on intermediate hydrophobic SiO₂ nanoparticles stabilized water-in-Hexane emulsion, colloidosome microcapsules Alg/SiO₂ with alginate gel cores and shells of SiO₂ nanoparticles were prepared by chelation with calcium cations from in situ release. Insulin microcrystals as water-nonsoluble drug were encapsulated into Alg/SiO₂ colloidosome microcapsules by dispersing them in the alginate sodium aqueous solution before emulsification. The sustained release of Insulin microcrystals could be obtained in model release medium due to the advantage of two levels of encapsulation of alginate gel cores and shells of SiO₂ nanoparticles. Meanwhile the whole release curves were respectivelly fitted by Monoexponential equation, Higuchi equation, the Weibull equation and Hixson-Crowell equation. The release mechanism could be explained by the Weibull equation. The fitted results of the Weibull equation proved that the drug release from the colloidosomes followed Fick diffusion.2. The colloidosome used as a biomimetic reactor was demonstrated at the first time. The colloidosome microcapsules with SiO₂ nanoparticle shells and gellan gel cores were facilely and efficiently prepared by self-assembly of colloidal particles at the liquid-liquid interfaces and subsequently in-situ gelation of gellan gum by reducing the temperature. The urease-loaded colloidosomes were used as an enzymatic reactor to produce calcium carbonate precipitates by urease-catalyzed urea hydrolysis in the presence of calcium cation. The CaCO₃/SiO₂ shells were formed around the gellan gel cores at the end of the reaction.3. SiO₂ nanoparticles could self-assembly at liquid-liquid interfaces to form stable water-in-oil inverse Pickering emulsion. Monomers dissolving in suspended aqueous droplets were subsequently polymerized at different temperatures. The hollow microcapsules with SiO₂/PNIPAm nanocomposite shells were obtained when the reaction temperature was above the lower critical solution temperature （LCST） of PNIPAm. While the core-shell microcapsules with SiO₂ nanoparticles shells and PNIPAm gel cores were produced when the polymerization was conducted at the temperature lower than LCST using UV light radiation. The interesting properties of both microcapsules were their ability of reversibly swelling during drying/wetting cycles and responsive to temperature stimulus. Such functional microcapsules may find applications in double control release system due to the presence of the supracolloidal structures and thermo-sensitivity.4. A series of w/o/w or o/w/o emulsion stabilized only by two different types of solid particles were prepared by a two-step method. We explored the option of particular emulsifiers for the Pickering multiple emulsions and a variety of nanoparticles （silica, iron oxide and clay particles） only differing in their wettability was used. The primary w/o emulsion was obtained by the hydrophobic particles, and then the hydrophilic particles were used as in the secondary emulsification to prepare the w/o/w emulsions. In a similar way, the primary o/w emulsion of the o/w/o emulsions were stabilized by the hydrophilic particles, while the secondary emulsification to prepare the o/w/o emulsions were effected with the hydrophobic silica. The resultant multiple emulsions are stable to coalescence for more than 3 months, except the w/o/w emulsions of which the secondary emulsion stabilized by clay particles become a simple o/w emulsion in a day after preparation. Moreover, the introduction of the temperature and pH sensitive poly（N-isopropylacrylamide） （PNIPAm） microgels could obtain the stimulus-responsive multiple emulsions. Such microgels stabilized multiple emulsions could realize the efficient controlled release on demand in a multiple-emulsion delivery system. 5. The nanocomposite multiple-core polymer microspheres with supracolloidal structures were obtained by the multiple Pickering emulsion polymerization at the first time. The oil soluble monomer （styrene） and the water soluble monomer （acrylamide or N-isopropylacrylamide） were respectively added into the solid stablized the w/o/w and o/w/o emulsion,and then polymerized to prepared the l multihollow polystyrene microspheres and multihollow gel microspheres. In the nanocomposite multiple-core polymer microspheres, the first nanoparticles mainly located on the surface of inner pores and the second nanoparticles mainly located onto the shell of the whole microsphere; this composite structure were confirmed by the CLSM, SEM, TG and FITR. The oil soluble monomer （styrene） and the water soluble monomer （acrylamide） were added in the oil phase and the inner water phase of he multiple Pickering emulsion （w/o/w）, and then simultaneously polymerized to obtain the composite multiple-core PS-PAm microspheres. The inner structure of nanocomposite PS/PAm microspheres is porous and each pore is not interconnected. The independent pores inside the microspheres also suggests that the high stabilization of the multiple emulsion in the polymerization process. It was found that after drying, the surfaces of the inner pore were covered with a nodular structure by the PAm gel.更多还原