【作者】 吴霞；

【导师】 巫辉；

【作者基本信息】 武汉理工大学 ， 应用化学， 2010， 硕士

【摘要】 纳米粒子由于表面效应、体积效应、量子尺寸效应及宏观量子隧道效应等能够表现出奇特的光、电、磁、热等性能而使纳米材料具有极大的应用潜能。然而纳米粒子的稳定性及形貌、尺寸的可控性成为限制其进一步发展的重要因素。本工作目的在于借助乳液方法,制备稳定的、尺寸及形貌可控的金属纳米粒子及聚合物纳米粒子,并研究其内部规律。通过反相微乳液体系中的化学还原方法来制备银纳米粒子。XRD、TEM及UV-Vis等表征结果表明,参数的改变影响反相微乳液的形成及稳定性,选择OP-10代替AOT作乳化剂能有效地缩短反应时间,在反相微乳液体系中液滴间以相互吸引的方式进行的物质交换是动力学的控制因素,由布朗运动所产生的碰撞是动态交换的动力；在最佳反应条件下得到的产物为稳定的球形单分散银纳米粒子,平均粒径15.2nm,内部结构规整,为面心立方单晶结构。本论文在乳液聚合中用银氨络合物作过硫酸钾的分解促进剂快速制备聚苯乙烯纳米粒子。首先讨论了反应温度、搅拌速率、油水质量比、乳化剂用量等因素对苯乙烯乳液聚合的影响,确定出最佳反应条件；动力学研究结果表明过硫酸钾-银氨催化下,苯乙烯单体的转化速率明显提高,一开始乳液聚合的速率就达到最大,之后速率一直下降,在较短时间内反应结束并且转化完全,银氨的加入降低了引发剂过硫酸钾的引发活化能,使得苯乙烯乳液聚合最低温度降低,体系的表观活化能也明显降低。FT-IR、DSC、TEM及GPC表征结果表明,过硫酸钾-银氨对聚苯乙烯的结构、形貌及玻璃化转变温度没有影响,但在其作用下,较传统乳液聚合而言,聚苯乙烯纳米粒子的粒径较小,温度升高粒径减小的同时分布也变窄,而分子量降低了一半左右,分布稍稍变宽；银氨的加入具有双重作用,不仅对过硫酸钾的分解有促进作用,使苯乙烯乳液聚合经典乳液聚合机理,聚合场所在胶束内并且仅有胶束成核一种方式,此外,银氨络合离子还具有协助表面活性剂稳定乳胶粒的作用。使用银氨作促进剂进行苯乙烯的快速乳液聚合的研究才刚起步,其促进机理、对其他单体乳液聚合的作用等相关问题的深入研究在理论及工业应用上均具有重大意义。更多还原

【Abstract】 Nanomaterials have great potential application since these nanoscale particles can exhibit peculiar optical, electrical, magnetic and thermal properties due to Surface effect, volume effect, quantum size effect and macroscopic quantum tunneling effect and so on. However, the stability and the controllability of their size and morphology becomes an important factor to limit the further development. This work aims at preparing stable size&morphology controlled metal nanoparticles and polymer nanoparticles as well as studying the mechanmism.Silver nanoparticles are prepared by the chemical reduction in reverse microemulsion. XRD, TEM, UV-Vis and other characterization results show that the formation and stability of microemulsion system are affected by the changing parameters, the reaction time is effectively shorten by selecting OP-10 instead of AOT as emulsifier, the reactants exchange between the droplets via attractive interactions is the control factor of dynamics in the reverse microemulsion system. The obtained stable monodispersed silver nanoparticles under optimum conditions are spherical monocrystalline with an average diameter of 15.2nm.The polystyrene nanoparticles are rapidly synthesized in emulsion polymerization via using the silver ammonia complex as accelerator to promote the decomposition of potassium persulfate. We first discuss the reaction temperature, stirring speed, oil-water mass ratio, emulsifier density etc influence in the period of styrene emulsion polymerization to determine the best reaction conditions. Kinetic results show that under the catalysis of KPS-silver ammonia, the styrene monomer conversion rate is significantly enhanced, the polymerization ends in a short time with the maximum rate at the beginning followed by continuous decreasing and the conversion is complete. The adding of silver ammonia decreases the initiator activation energy of potassium persulfate, lowering the minimum polymerization temperature of styrene and significantly decreasing the apparent activation energy of the reaction system.FT-IR, DSC, TEM and GPC characterization results showed that KPS-silver ammonia does not affect the structure, morphology and glass transition temperature of polystyrene. But under its effect, when compared with the traditional emulsion polymerization, the sizes of polystyrene nanoparticles are smaller, the size and size distribution are both decreased with increasing temperature; the molecular weight reduce by half with a slightly wider distribution. The addition of silver ammonia has a dual role, not only promoting the decomposition of potassium persulfate so that the styrene polymerization does not comply with the classical polymerization mechanism for the polymerization sitting in the micelles and there only exist micellar nucleation, but also assisting the surfactant to stabilize latexes. It has just started to use silver ammonia as promoter for the rapid polymerization of styrene and it’s of great significance both in theory and industrial applications for depth study of related issues such as the promotion mechanism, the effect in other monomer polymerization and so on.更多还原