【作者】 张魁；

【导师】 郭锴； 毋伟；

【作者基本信息】 北京化工大学 ， 化学工程， 2010， 博士

【摘要】 随着界面科学和技术的发展,可以通过“精细结构设计”得到具有各种特殊结构(核-壳、胶囊等)的纳米复合颗粒,并获得各种特有的应用性能,可以更好的使聚合物材料和无机材料的优势得到互补。目前,针对具体应用的特点和功能对材料进行设计,制备出适合应用性能的材料是科学界和工业界共同努力的目标。鉴于此,本文采用新颖的Pickering乳液聚合法,制备了具有特殊结构的聚苯乙烯／二氧化硅复合微球、磁性复合微胶囊、核壳结构聚丙烯酰胺／二氧化硅复合微球以及温敏性聚N-异丙基丙烯酰胺／聚甲基丙烯酸甲酯／二氧化硅复合微胶囊,并系统地研究了各制备过程的影响因素、产品的形成机理及应用性能。全文主要研究内容如下：1.以具有反应性的γ-甲基丙烯酰氧基丙基三甲氧基硅烷为改性剂对纳米二氧化硅颗粒进行表面改性,考察了改性溶剂类型、溶剂中水相pH值、溶剂中水含量、改性剂质量以及改性温度对改性效果(接触角)的影响。研究表明：环己烷／水混合改性溶剂、弱酸性水相、溶剂中水含量略高于所加硅烷水解所需水量、改性温度50-70℃,有利于二氧化硅的表面改性。所制备的改性二氧化硅在水中有所团聚,在乙醇中分散性较好。2.选择具有反应性的单体苯乙烯作为油相,二氧化硅颗粒作为稳定剂,考察了苯乙烯／水／二氧化硅的Pickering乳液体系的性质。颗粒的表面润湿性(接触角)与颗粒润湿顺序对颗粒在油水(苯乙烯,水)体系中所处的位置以及所制备乳液的类型都有明显影响。具有强亲水(接触角为9.2°)或强疏水(接触角为128.5°)表面的颗粒完全分散在水相或苯乙烯相中,不能起到稳定乳液的作用,只有具有适中润湿性的颗粒能够稳定乳液。用适中亲水性(接触角41.5°)的固体颗粒作为稳定剂,制备了O／W型乳液体系,实验结果表明,二氧化硅颗粒表面电荷越低或固体颗粒浓度越高或乳液所处温度越低,有利于Pickering乳液稳定性的提高。乳液液滴粒径随着固体颗粒浓度的增加而减小。3.以苯乙烯作为内相,去离子水作为连续相,改性二氧化硅作为稳定剂,采用O／W型Pickering乳液聚合法成功制备了核壳结构的聚苯乙烯／二氧化硅纳米复合微球。借助于TEM、SEM、IR、TG以及XPS等测试手段对其进行了表征。结果表明：在复合微球结构中,苯乙烯球为核,氧化硅颗粒为壳,微球粒径为1-1.4μm左右；通过调节固体颗粒浓度或颗粒表面润湿性或颗粒表面电荷电量可以影响Pickering乳液聚合过程,得到两种不同结构的产物：核壳结构复合微球或聚苯乙烯球与二氧化硅共混物。经测试,核壳结构复合微球较聚苯乙烯球与二氧化硅共混物具有更高的分解温度。4.用改进的Pickering乳液聚合法,成功制备了具有磁性的复合微胶囊。磁性复合微胶囊粒径在0.8-2μm左右,壁厚为140nm左右,微胶囊囊壁具有双层结构：外层为二氧化硅固体颗粒层,内层为聚合物层,而且磁性颗粒定位于聚合物层中。复合微胶囊具有超顺磁性,分散在溶液中时,能够被外加磁铁富集。采用原位载药的复合微胶囊在释放溶剂中具有药物缓释性能。5.以丙烯酰胺水溶液作为内相,液态石蜡作为连续相,改性二氧化硅颗粒作为稳定剂,采用反相Pickering乳液聚合法成功制备了聚丙烯酰胺／二氧化硅复合微球。复合微球粒径约在2-4μm左右,聚丙烯酰胺为核、二氧化硅为壳。制备过程中,丙烯酰胺浓度和固体颗粒浓度对于聚丙烯酰胺／二氧化硅复合微球的形成有显著影响。聚丙烯酰胺／二氧化硅复合微球对废水中Hg2+有较强的吸附性能,复合微球对Hg2+的吸附在弱酸条件下效果较好,受吸附温度影响不大。吸附温度在30℃时,复合微球的吸附等温线可以用Langmuir等温方程很好的拟合。另外,复合微球对Hg2+吸附过程符合拟一级吸附动力学模型。6.以N-异丙基丙烯酰胺水溶液作为内相,液态石蜡作为连续相,甲基丙烯酸甲酯和二乙烯基苯作为外相单体,改性二氧化硅颗粒作为稳定剂,采用反相Pickering乳液聚合法成功制备了具有温敏性的聚N-异丙基丙烯酰胺／聚甲基丙烯酸甲酯／二氧化硅复合微胶囊。复合微胶囊粒径为3μm左右。微胶囊囊壁具有双层结构,外层为二氧化硅固体颗粒层,内层为聚合物层,总厚度约为290nm。微胶囊具有温敏性并且其壁层厚度可以通过改变聚合前所加入甲基丙烯酸甲酯的质量进行调节。复合微胶囊可以作为药物载体,在药物释放过程中,可以通过控制微胶囊壁厚或调节释放溶剂温度来调控药物的释放速率。7.尝试利用旋转填充床作为乳化设备制备反相Pickering乳液。固体颗粒浓度、旋转填充床转速以及循环时间对所制备Pickering乳液稳定性均有影响。在一定条件下,较高的固体颗粒浓度或较快旋转填充床转速或较长的循环时间有利于Pickering乳液稳定性的提高。所形成乳液液滴的粒径随着所用固体颗粒浓度的增加或旋转填充床转速的提高或循环时间的延长而变小。更多还原

【Abstract】 With the development of interface science and technology, We can obtain nano-composite particles with various structures (core-shell, capsule, etc) by "design of structure" and get different specific application performances. In this way, the advantages of polymer materials and inorganic materials can be linked. At present, according to features and functions of practical application to design materials and prepare applicable materials are the common goal of scientific community and industrial circles. In this thesis, polystyrene/nano-SiO2 composite microspheres (PS/nano-SiO2) with core-shell structure, magnetic polymer enhanced hybrid capsules, poly(acrylamide)/silica hybrid microspheres and poly(N-isopropyl-acrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from Pickering emulsion polymerization. The preparations, characterizations and applications of these materials were studied. The main research works are summarized as follows:1. Nano-silica particles were modified by y-methacryltrimethoxysilane. The effects of solvent type, pH value of water in solvent, water content in solvent, mass of modifier and temperature for modification on modification (contact angle) were investgated. The results indicated:cyclohexane/water solvent, slightly acidic aqueous phase in solvent, lower water content and reaction temperature of 50-70℃are better for modification. The prepared modified silica particles aggregate in water but well dispersed in ethanol. 2. Pickering emulsion (styrene/water) stabilized by silica nanoparticles were investgated here. The following conclusions are drawn:Particle wettability and the priority wettability have significant effect on the particles location in Pickering emulsion system, and the type of prepared emulsion. Solid particles with too hydrophilic (contact angle is 9.2°) or hydrophobic (128.5°) can not be used as a stabilizer for emulsion preparation. The particles with moderate hydrophilicity (41.5°) can stabilize O/W emulsions;For the particles (with a contact angle of 87.2°), the prior wettibility decide the type of emulsion-the O/W emulsion is formed when particles are dispersed in water preferentially, W/O emulsion is formed when particles are dispersed in styrene preferentially. For O/W emulsion stabilized by the particles with a contact angel of 41.5°, the lower particle surface charge or higher particle concentration or lower emulsion temperature are better for the stability of as-prepared emulsion. The droplet size in Pickering emulsion decrease as increasing the particle concentration.3. Polystyrene/nano-SiO2 composite microspheres (PS/nano-SiO2) with core-shell structure were successfully synthesized in a Pickering emulsion route using nano-SiO2 particles as stabilizers, which were organically modified by methacryloxypropyl-trimethoxysilane (MPTMS) which containing a reactive C=C bond. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transformation infrared spectrum (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). In addition, bare PS spheres could also be obtained by changing synthetic conditions. It was found that the morphology of the resulting products depends on particle concentration, particle wettability and pH value of particle dispersion. A possible mechanism for the formation of the composites with different morphologies is proposed.4. Magnetic polymer enhanced hybrid capsules (MPEHCs) were successfully prepared from a novel Pickering emulsion polymerization. The resultant products were characterized by Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectrum (FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Vibration sample magnetometer (VSM). It was proved that the MPEHCs consist of SiO2 outer shell and magnetic polymer inner shell with particle sizes from 0.8μm to 2μm and thickness about 140 nm. The MPEHCs were applied as a drug carrier to study their controlled release behaviors and ibuprofen was used as a model drug. The curve of release behaviors of ibuprofen exhibited a typical sustained release pattern, indicating that the MPEHCs could be applied as a promising drug vehicle for controlled release systems.5. Poly(acrylamide)/silica hybrid microspheres were prepared from inverse pickering emulsion polymerization using a acrylamid aqueous solution as the inner droplets, liquid paraffin as the outer continuous phase and modified silica nanoparticles as stabilizers. These hybrid capsules sized about 2-4μm, and they contained a solid silica shell and a Poly(acrylamide) core. In the process of the preparation, both the concentrations of AM and solid particles can bring a notable influence on the synthesis of the capsules. The prepared Poly(acrylamide)/silica hybrid microspheres had a strong adsorption of Hg2+ in the wastewater and the effect of the adsorption, which is not much influenced by temperature, can be better in the weak acid condition. At 30℃, the adsorption isotherms fit the Langmuir isotherms equation very well. Meanwhile, the adsorption of Hg2+ by the hybrid microspheres agrees with Pseudo-first-order adsorption kinetic process.6. Poly(N-isopropylacrylamide)/poly(methyl methacrylate)/silica hybrid capsules were prepared from inverse Pickering emulsion polymerization. A N-isopropylacrylamide aqueous solution was emulsified into an oil phase containing methyl methacrylate and divinyl benzene by sonication to obtain a W/O Pickering emulsion using modified silica nanoparticles as stabilizers. After the emulsion was polymerized, the hybrid capsules were obtained. The capsule wall contained two layers-a solid particle monolayer and a polymer layer and the wall thickness could be controlled by adjusting the methyl methacrylate and divinyl benzene concentrations in the continuous oil phase before polymerization. The as-synthesized capsules exhibited temperature-responsive properties. The controlled release experiments showed that the release rate of a model drug from the hybrid capsules could be controlled by adjusting the wall thickness of the capsule or the temperature of the release medium. 7. Rotating packed bed was used to prepare inverse Pickering emulsion. The stability of the Pickering emulsions has a relationship with the solid particle concentration, rotating speed and circulaton time. Higher particle concentration or rotating speed and longer circulation time can improve the stability of Pickering emulsions. Emulsion droplet size becomes smaller as increment of particle concentration or rotating speed, or extension of circulation speed.更多还原