【作者】 王小军；

【导师】 胡道道；

【作者基本信息】 陕西师范大学 ， 化学工艺， 2007， 硕士

【摘要】 模板法制备具有特殊结构和性能的复合微球材料是当今材料科学领域的研究热点，其优势在于模板的自身结构和形貌特征可对合成材料的大小、形貌、结构等进行有效控制，同时也可根据合成材料的大小和形貌预先设计模板。此外，还可以实现纳米尺寸颗粒与大尺度模板间的有效复合，该复合材料在整体上的大尺寸和表面纳米级复合物为其在很多方面的应用创造了极为有利的条件。高分子微凝胶具有独特的分子内交联结构，并在良性溶剂中具有可逆的溶胀特性。因此，以高分子微凝胶为模板，可以制备具有特异微结构特点的复合材料。本论文工作正是基于这一基本思路，提出了通过冷冻干燥技术处理水溶胀的聚丙烯酰胺微凝胶，并以得到的多孔结构凝胶微球为模板制备新型复合材料的新方法。通过控制多孔模板微球的形成条件及复合材料的制备条件，成功可控性地获得具有特异孔道结构和表面形貌的无机．有机复合微球材料。依据上述研究思路，开展了以下几个方面的工作。（1）采用反相悬浮聚合法合成了聚丙烯酰胺（PAM）高分子微凝胶，利用微凝胶在良性溶剂中的溶胀作用，通过冷冻干燥处理得到具有规则均匀多孔道结构的球形材料。运用扫描电镜表征手段对凝胶微球的表面结构进行了检测。研究表明：通过调节PAM微凝胶中的交联剂-N，N′-亚甲基双丙烯酰胺（BA）的含量，可实现对PAM凝胶材料孔道结构的有效调控。随着微凝胶中交联剂含量的增加，多孔凝胶的孔道交联度增加，孔壁刚性增强，凝胶微球孔径减小、孔壁变薄，且该微凝胶为无定型态。BET和压汞法研究结果表明：该微凝胶是一种兼备大孔（孔尺寸＞50nm）和微孔（孔尺寸＜2 nm）的凝胶材料。这一研究结果为制备具有多级孔径分布的多孔结构的有机-无机复合微球材料提供了一个新途径。（2）采用具有多孔道结构的PAM高分子微凝胶为模板，将前驱体钛酸四丁酯（TBOT）浸渍的模板微球置于密闭潮湿气氛中发生原位水解缩合反应制备了具有多级表面结构的PAM／TiO₂有机-无机复合微球。利用扫描电子镜（SEM）、红外光谱（FT-IR）、热重分析（TGA）、X-射线衍射分析（XRD）、BET、压汞法等检测手段对复合微球的表面形貌、无机沉积物的相对含量、晶型和相对应的孔参数等进行了表征。实验表明：微凝胶中交联剂BA的含量、前驱体TBOT的浓度、环境气相中的湿度以及前驱体浸渍液在凝胶模板上的残留量等因素对复合微球表面形貌产生显著影响。随着BA含量的增加，PAM凝胶的孔尺寸明显减小，相应的PAM／TiO₂复合微球的孔尺寸可以得到相当调节；改变凝胶模板上的浸渍液残留量和沉积反应气氛中的湿度，可有效控制PAM／TiO₂复合微球的表面形貌；前驱体TBOT的浓度对复合微球表面形貌和孔结构也会产生显著的影响。尽管上述研究结果说明复合微球形貌的控制极为复杂，但这种复杂性也为复合微球表面形貌的调控带来了许多优势，即形貌可控的多元化。整体而言，通过改变以上反应参数，可以得到三种典型表面形貌的复合微球：①表面被大尺寸TiO₂微球致密覆盖的复合微球；②较大粒径的TiO₂微球稀疏分布于多孔复合微球表面，而较多地沉积于孔道内壁；③均匀分布有小粒径TiO₂的大孔表面结构的复合微球。基于这种复合材料微观结构优越的可调性，复合微球微米级尺寸的易分离性，纳米级表面结构的表面活性，使这种多孔材料有望在构筑微反应器、制备吸附分离材料等方面得到较为广泛的应用。这种方法将有望成为制备多种类型多孔有机-无机复合微球材料的新方法。（3）采用具有多孔道结构的PAM微凝胶为模板，提出了在室温下，利用气相中的水合肼还原浸渍在多孔凝胶模板上的前驱体硝酸银来制备PAM／Ag多孔道结构复合微球的新方法。实验系统研究了不同前驱体浓度和不同模板组成对复合微球表面结构的影响。SEM及XRD表征结果表明：通过调节模板微球的交联剂BA含量可有效控制多孔复合微球的孔隙率。通过调节前驱体浸渍液AgNO₃的浓度，可以有效控制复合微球上Ag单质的担载量。同时，实验结果说明：利用多孔模板微球对客体分子的空间限域作用可有效地对客体起到分散作用，可以很好地控制客体分子的聚集行为，并实现对客体分子结晶粒径的有效控制。该研究结果对于制备具有催化活性及杀菌性能的复合微球材料具有重要的借鉴意义。更多还原

【Abstract】 Recently, template method on preparation of composite materials with special structure and properties has become the focus of active research. The template method is superior to other approaches, in which the size, structure and morphology of the prepared materials can be controlled and adjusted by simple altering the nature of template and the preparation conditions. Moreover, template can be predesigned in the size and shape of objective materials.Polymer microgels are microsphere materials with similar structures of bulk gels. The three-dimentional network structure appears in rich solvent, and then porous microgles with unusual surface morphologies after treatment of microgles can be obtained. Additionally, the organic-inorganic composite microspheres with hierarchical surface morphologies can be feasibly gained using the controllable porous microgels as template. Based on the idea mentioned above, the research in this thesis includes the following parts.（1） The polylacrylamide （PAM） microgels are prepared by inverse suspension polymerization method, and porous PAM microgels are prepared by the freeze-drying treatment of the swollen microgels. The different surface morphology of porous PAM microgels can be obtained by adjusting the content of cross-linker-N, N’-methylene bisacryamide （BA） in microgels. The surface morphology of porous microgels can be controlled in the swollen degree of microgels and the content of cross-linker in microgels. SEM and X-ray diffraction measurements are empolyed to monitor the porous surface structures and the crystallographic state. The research results show that the surface morphology in the pore size and pore volume regularly change with the content of cross-linker, and the microgels are amorphous. The results of BET and mercury injection method analysis indicate that the pore size in the porous microgels are commonly divided into macropores （the pore size＞50 nm）, and micropores （the pore size＜2 nm）. Based on these results, a novel approach for preparation organic-inorganic composite microspheres with porous structure surface morphology could be set up.（2） Utilizing the porous PAM microgels as templates, PAM/TiO₂ composite microsheres with hierarchical surface morphologies are prepared by in situ hydrolysis and condensation of tetrabutyl titanate located at the templates in a moist atmosphere. The morphology and constitute of composite microspheres are characterized by SEM、FT-IR、TGA、XRD、Brunauer-Enmet-Teller and mercury injection method analysis, respectively. The results indicate that the composite microspheres with different hierarchical surface morphologies could be obtained by controlling the cross-linking degree of the porous PAM microgels, the relative humidity of the gas phase, the amount of residual impregnation liquid and the TBOT concentration in the porous PAM microgels. Although the surface morphologies of the composite microspheres are varied, the morphologies are typically divided into three categories: （1） wrinkled surfaces covered with large dense TiO₂ particles; （2） porous structures sparsely suffused with large TiO₂ particles along the fringes and inner walls of the porous channels; （3） macroporous surfaces with small TiO₂ particles distributed ubiquitously. The incorporation of TiO₂ particles into PAM microgels resulted in an obvious increase in specific surface area, and the pore size distribution of the microspheres depended strongly on the size of TiO₂ particles.（3） Based on the porous PAM microgels as template, the porous structure PAM/Ag composites microspheres are prepared by in situ reduction of silver nitrate by hydrazine hydrate in a closed container at room temperature. The SEM results show that the composite materials with different surface morphologies and porous structure can be obtained by changing the reaction conditions. According to the results, the pore parameter and specific area of the composite materials can be effective adjusted. Additionally, Ag particles loaded on the composite microspheres are homogeneously distributed. XRD spectra demonstrate that the composite material is amorphous. The PAM/Ag composite material has a potential application in catalysis and adsorption due to the property of Ag and the regular porous structure.更多还原