基于微凝胶模板法制备核—壳型有机—有机复合微球研究

【作者】 孙莉峰；

【导师】 张颖；

【作者基本信息】 陕西师范大学 ， 物理化学， 2008， 硕士

【摘要】 核-壳型材料是一类由中心粒子为核,不同组分为壳层而组成的复合型材料,由于其在组成、结构、表面性质等方面具有可调控性和可剪裁性等特点,这类材料的制备和应用研究已成为众多学科领域的科学家们关注的热点课题。模板法由于具有方法简单、重复率高、预见性好、产品形态均一、性能稳定等诸多特点而被广泛用于制备核-壳结构材料。根据化学组成的不同,模板可分为有机模板和无机模板。其中,有机模板因其结构的多样性和尺寸的可控性等特点,已成为制备核-壳型材料的有效方法之一。与其它有机模板材料相比,高分子微凝胶由于(1)制备方法简单、容易引入反应性基团,尺寸大小可控;(2)对外界刺激如温度、pH值、离子强度、光、电、磁等有明显的体积变化等特点,已成为制备多种类型具有特异形貌和特殊性能的微纳米材料复合材料的理想模板。在实验室已有研究工作的基础上,本论文开展了基于高分子微凝胶模板制备具有特异表面结构的有机-有机复合微球材料的研究工作。以丙烯酰胺为反应单体,利用反相悬浮聚合法制备得到了聚丙烯酰胺高分子微凝胶,通过控制不同的反应条件,实施甲醛和尿素的缩聚反应,得到了两种具有不同表面形貌的聚丙烯酰胺/脲醛树脂有机-有机复合微球材料,主要研究内容包括以下两个方面:(1)利用反相悬浮聚合法制备出聚丙烯酰胺微凝胶,以其为反应模板,在反相悬浮体系中实施甲醛和尿素的缩聚反应,即将脲醛树脂的形成反应控制在油、水相界面上进行,从而得到脲醛树脂和聚丙烯酰胺两种组分均匀复合的微球材料。实验结果表明,甲醛和尿素溶液的pH值、甲醛和尿素溶液的浓度、甲醛和尿素的摩尔比以及模板微凝胶的化学组成等因素对复合微球的表面结构产生重要的影响。(2)以聚丙烯酰胺高分子微凝胶为模板,在微凝胶/气相界面原位实施甲醛和尿素的缩合反应,在一定温度条件时得到具有典型核-壳结构的有机-有机复合微球材料。通过改变甲醛和尿素溶液的pH值、甲醛和尿素溶液的浓度、甲醛和尿素的摩尔比、模板化学组成等条件可以得到具有草莓状表面结构特征的脲醛树脂/聚丙烯酰胺复合微球材料。该合成技术方法简单,且适于大量制备。利用扫描电子显微镜(SEM)、热重分析(TGA)、红外(FT-IR)等手段对样品的形态、结构和组成进行了表征。更多还原

【Abstract】 Core-shell structure materials are a kind of composite materials that composed of central particles as "core" and different components as "shell" layers. The preparation and application research of core-shell structure materials have aroused many scientist’s interests because of their controllable and tunable special features in composition, structure, and surface properties. Template methods have been extensively used for preparing core-shell structure materials due to their simplicity, high repeating ration, being foreseeable, uniform product morphology, and stable properties. Template can be divided into organic and inorganic types according to their chemical compositions. Organic template have become one of an effective approach for synthesis core-shell materials based on their structure’s diversity and size’s controllability. Compared with other organic templates, polymer microgels have become a kind of ideal template material for preparing micro- or nano- composites with special morphologies and properties. This is because polymer microgels have the advantages of simple synthesis, adjustable chemical functionality, and the controllable sizes. In addition, polymer microgels have stimulus-responsive volume changes, where the stimuli could be temperature, pH, electric and magnetic fields, etc.Based upon the previous work in our group, in this study, we focus on research interest on the synthesis of organic-organic composite microspheres with special surface structures using the polymer microgel template. Polyacrylamide (PAM) microgels were produced by the inverse suspension polymerization technique using acrylamide as monomer. Two types of Urea-formaldehyde resin (UF Resin)/PAM composite microspheres with different surface morphologies were prepared by conducting the polycondensation between formaldehyde and urea via controlling the different reaction conditions. This thesis includes two parts as follows:(1) Polyacrylamide microgels were produced by the inverse suspension polymerization technique. The UF Resin/PAM composite microspheres with novel surface morphology were prepared via polycondensation between formaldehyde and urea in the inverse suspension system using PAM as a reaction template. It was demonstrated that the surface morphologies of the composite microspheres could be controlled by varying the pH value and concentrations of the formaldehyde and urea solutions, the molar ratio of formaldehyde to urea and the composition of the used template.(2) Using PAM mierogel as template, the UF Resin/PAM composites microspheres with typical core-shell structure were prepared by in-situ polycondensation of formaldehyde and urea between the microgel and gas interface under the stated temperature. The research results indicate that the as-prepared composite microspheres with raspberry-like morphologies could be obtained by controlling the pH value and concentrations of the formaldehyde and urea solutions, the molar ratio of formaldehyde to urea and the composition of the used template. The approach we proposed is characteristics of facile and mass.The morphologies, the structure and the composition of composite microspheres were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared spectrometer (FTIR) techniques, respectively.更多还原