【作者】 王杰；

【导师】 刘奉岭； 孙祉伟；

【作者基本信息】 山东师范大学 ， 物理化学， 2009， 硕士

【摘要】 胶体粒子在一定条件下可以像原子那样,形成三维有序结构,称之为胶体晶体。胶体晶体由于可以作为时间和空间上放大的晶体模型用来研究原子晶体的成核和生长过程,并且还可以构成具有特殊光学特性的光子晶体,从而引起科学家和工程师的研究兴趣。我们在胶体晶体研究方面所开展的主要工作可以概述如下:1、我们制备一系列的单分散的聚苯乙烯/磺酸钠和二氧化硅颗粒,用于组装胶体晶体。单分散的二氧化硅主要通过stober法和生长硅溶胶方法制备。考察了stober合成法中正硅酸乙酯(TEOS),氨水,水,温度对颗粒粒径和单分散性的影响。结果显示,stober方法对生长环境比较敏感,产率不高。但是,这种方法是研究颗粒生长机制和制备粒径小于100纳米的较小二氧化硅颗粒仍是一种有效的途径。种子生长法是制备高产量的二氧化硅的常用方法。与stober方法相比,它具有如下的优点,最终产品颗粒的数目由硅溶胶的数目决定,颗粒的最终粒径可以根据添加的正硅酸乙酯的量来预测,而其此方法制备的二氧化硅的产率高,适合工业大规模生产。但是,必须要求颗粒的最终直径大于5倍硅溶胶种子的粒径,也就是说,粒径在100nm以上比较合适。单分散的聚苯乙烯/磺酸钠是通过乳皂聚合方法制备,分析了引发剂用量、电解质浓度、单体浓度等因素对聚苯乙烯颗粒物理化学性质的影响,结果显示乳液聚合制备的聚苯乙烯/磺酸钠颗粒具有较高的表面电荷和较好的单分散性。2、我们采用密度匹配法研究了重力对带电粒子胶体晶体的影响。从原子分子层次认识材料的结构对于其性能的研究是非常必要的。由于胶体粒子与原子分子相比更容易被观察和研究,因此胶体晶体可以作为原子晶体的模型体系来认识和研究材料中的原子行为。然而,胶体晶体的弹性模量非常低,很小的外场就可能改变胶体晶体的结构。在本文中,我们将重水(D2O)和水(H2O)以一定比例混合来匹配直径为110nm的聚苯乙烯带电小球的密度,并利用Kossel衍射方法测量了胶体晶体的结构和晶格常数等参数。通过将密度匹配(g=0)和没有进行密度匹配(g=1)的实验结果的对比,我们发现重力将会使样品池中胶体晶体的晶格常数随高度的变低而变小。这一结果表明,在带电粒子胶体晶体的研究中有必要考虑重力的影响。3、采用光固化技术,以丙烯酰胺单体与亚甲基双丙烯酰胺交联剂在紫外光的照射下发生光聚合反应,嵌入聚苯乙烯胶体晶体,实现了胶体晶体的固定化。结合反射光谱和Kossel衍射技术研究对照了固定化前后胶体晶体的变化,实验结果表明,通过这种水凝胶固定化的胶体晶体保存了未固定前悬浮液中胶体晶体的结构。但固定化后的胶体晶体的晶面间距和晶体的尺寸都略微减小。通过对固定化后的水凝胶长时间的反射光谱观测,发现固定化后胶体晶体在Milli-Q水中起初会发生溶胀,经过2-5天溶胀-消溶胀过程达到平衡,平衡后的水凝胶胶体晶体十分稳定,可以长时间保持胶体晶体的结构。因此,胶体晶体固定化不但极大地提高了悬浮液中胶体晶体的抗剪切能力,还克服了悬浮液中胶体晶体对离子、外界干扰的敏感性,扩大了胶体晶体的实际应用价值。更多还原

【Abstract】 The three-dimensional ordered structures are formed through a self-assembly process of colloidal particles like atoms at a certain condition, named colloidal crystals. Colloidal crystals have lately been of great interest to scientists and engineers because they can serve as a model system for studying the behavior of atoms on a much larger scale and photonic crystal with special optical effect. In this paper, a series of woks in the colloidal crystals are generalized in the following aspects:1. we synthesized a series of mono-dispersed sodium polystyrene sulfonate and Silica particles used for colloidal crystals. Mono-disperse silica particles were prepared two method-tradition stober and growth of silica sol particles. The factors which particle’s diameter and poly-dispersity index dependent on , such as the tetraethylorthosilicate (TEOS), ammonia, water and temperature, were investigated in stober method. It showed that stober method is sensentive to the growth environment, and have low silica content, however it is the good way of study the mechanism of growth and preparation of smaller silica particles that is less than 100nm .seeded growth of monodispered silica particles was described in this paper to shed new way for high content products. In constrast to stober method, seeded growth has the advantage that the end number of silica particles was determined by the number of silica sol and the diameter can be predicted according to the addition of TEOS. Besides, the high yields make it suitable for industry product. yet, it required that the designed diameter must be no less than 5 time of the dimeter of silica sol, that is mean that more than 100nm is more suitable. Mono-dispersed sodium polystyrene sulfonate particles was prepared by by using emulsifier emulsion polymerization, and then several factors such as initiator content, electrolyte concentration, monomer concentration etc. are discussed to discover the influences on physical chemistry properties of colloidal particles. Result demonstrates that the sodium polystyrene sulfonate particles have high surface charge density and monodispersity.2. Influence of gravity on crystallization of charged colloidal particles was studied by density-match. Understanding the structure of a material at the atomic level is essential to understanding its properties. Study of colloidal crystals holds great promise for modeling the behavior of atoms in materials because colloidal particles are more convenient to be detected and observed. However, elastic moduli of colloidal crystals are extremely low and thus even weak external fields can distort the structure of colloidal crystals. In this study, liquid mixtures of water (H2O) and deuterium oxide (D2O) as the liquid phase, was used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched (g=0) and unmatched (g=1) conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110nm (in diameter) polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.3. we immobilized colloidal crystals of charged particles in a poly (acrylamide) matrix by photoinduced polymerization. A reflection spectrum and Kossel-line diffraction were employed to trace and compare changes in the colloidal crystal structure before and after immobilization processing. Our experiments showed that immobilized colloidal crystals successfully retained the structure of colloidal crystals unless the sizes and the lattice spacings of the immobilized colloidal crystals decreased slightly. By observing the structure of immobilized crystals in Milli-Q water we confirmed that the lattice spacings of the crystals varied for several days initially during immobilization because of gel swelling or de-swelling. After reaching a balance (2-5 d), the immobilized colloidal crystals are found to be stable in Milli-Q water. Our study thus explores potential applications of colloidal crystals such as their use in photonic materials.更多还原