【作者】 徐明考；

【导师】 李丽芳；

【作者基本信息】 山东农业大学 ， 应用化学， 2010， 硕士

【摘要】 类水滑石（Layered Double Hydroxides,简称LDHs）是一类层状结构材料。由于LDHs具有特殊的层状结构和层间阴离子的可交换性,可将多种有机或无机阴离子引入水滑石层间,从而得到一系列具有不同功能的新材料。近年来,由类水滑石、蒙脱土等层状物有机化修饰得到的有机无机复合材料得到了越来越多的关注,广泛应用于催化、吸附、紫外吸收、控缓释及医药、高分子助剂等领域。流滴剂可使棚膜上的水滴快速流下而增大透光效果,因此在农业生产中有着重要的作用。目前市售流滴剂存在一些不足,如持效时间短,与其他助剂的相容性较差且薄膜保温性能较差等问题。本文以阴离子层状材料水滑石为插层主体,将非离子表面活性剂插入到层间,通过改变制备条件对材料组成、结构进行调控,制备一种新型层状结构有机-无机复合流滴剂,可以显著改善薄膜的流滴性能、保温性能。本文主要研究内容如下:1.利用共沉淀法制备了烷基糖苷改性类水滑石（APG-LDHs）,研究了其结构、热稳定性、插层驱动力及烷基糖苷在水滑石层间的排列方式。结果表明当pH=9,m（APG）/m[Mg（OH）₂+Al（OH）₃]=1/4,n（Mg）/n（Al）=2时,制备的样品有最大的层间距,晶体结构较为完善,无杂质;插层组装驱动力主要为静电引力和氢键作用,并且当烷基糖苷用量较少时,静电引力起主要作用;随烷基糖苷用量的增加,氢键作用逐渐增强;烷基糖苷分子在层间呈一定角度交错排列,角度范围为48.6°⁵4.8°;由于主客体之间的交互作用和水滑石层板的屏蔽效应,烷基糖苷插入层间后,热稳定性显著提高,分解温度提高约40℃。2.利用月桂酸、十四酸、十六酸、硬脂酸和十二烷基磺酸钠改性水滑石,对其结构进行表征,研究其在水滑石层间的排列方式,并选择最佳的改性剂作为制备复合流滴剂的载体。结果表明,表面活性剂改性水滑石的效果明显,其中月桂酸改性效果最佳;客体以双层倾斜的方式排列在层间。此外,十四酸-LDHs层间距分别增加到3.71 nm和4.37 nm,意味着其在层间有两种排列方式,十六酸-LDHs也具有两种排列方式。月桂酸-LDHs最佳制备条件:反应温度30℃,n（Mg）/n（Al）=2,pH=9。3.以月桂酸-LDHs为载体,采用二次组装法制备有机-无机复合流滴剂Span 20-lauric acid-LDHs,对其结构及其改性效果、PVC复合膜的表面性质进行了表征。结果表明Span 20-lauric acid-LDHs有机化程度高,在基质中均匀分散。Span20同时以吸附在表面和插层至水滑石层间的形式存在,添加Span20-lauric acid-LDHs后,PVC复合膜与水具有较好的亲和性,有效降低水在PVC复合膜表面的界面张力,从而获得优异的流滴性能。此外,新型有机-无机复合流滴剂可显著改善PVC复合膜的保温性能及透光性。更多还原

【Abstract】 Layered double hydroxides (LDHs), also named as anionic clays or hydrotalcite-like compounds, have a remarkable property that a variety of anionic species can be inserted as guests into the interlamella of the LDHs, especially beneficial organic anions, to form a large variety of new functional materials. Recently, Layered double hydroxides have attracted the attention of many researchers because of their potential application in the field of catalytic, adsorption, UV absorption, drug controlled release and polymer additives. Light transmittance of films could be improved by adding anti-dripping agent, therefore, it plays an important role in the agricultural production. At present, anti-dripping agent has some shortcomings, for example, the persistent period is short, lacking of compatibility between anti-dripping agent and other additives and the thermal insulation performance of film is very poor, and so on. In this paper, the surfactant was intercalated into Mg-Al-LDH interlayer by traditional co-precipitation method to form an organic-inorganic composite anti-dripping agent, and the possible effect factors were investigated.1. A series of APG-LDHs were synthesized by co-precipitation method. The optimum preparing conditions are pH 9, the mass ratio of APG/[Mg(OH)2+Al(OH)3] = 1/4 and the molar ratio of Mg/Al is 2. Besides electrostatic interaction, the driving forces of intercalation and assembly for APG molecules is hydrogen bonding between APG molecules and hydroxyl group of the host layers or interlayer water molecules. The interlayer APG molecules were arranged with a tilting angle between layers through hydrogen bonding, the range of the angleθis approximately between 48.6°~54.8°. Thermal decomposition temperature of APG between LDH layers increase about 40℃than pure APG, due to the strong host-guest interaction and the shielding effect of LDH layers.2. Mg–Al layered double hydroxide (Mg–Al LDH) was modified with lauric acid, myristic acid, hexadecanoic acid, stearic acid and sodium dodecyl sulfonate by co-precipitation method, and the resulting materials were characterized. The possible arrangement of surfactant in LDHs interlamellar space was also illustrated. The optimum modifier was selected as carrier of organic-inorganic composite anti-dripping agent. Comparison of performances of the resulting materials, we found that lauric acid is the optimum modifier. The interlayer surfactant molecules are arranged as a bilayer with a tilting angle. In addition, the d-spacing of myristic acid-LDHs increased to 3.71 nm and 4.37 nm indicating two types of arrangements are possible, and so does hexadecanoic acid-LDHs. The optimum preparing conditions for lauric acid-LDHs are the temperature are 30℃, the molar ratio of Mg/Al is 2 and pH 9.3. Organic-inorganic composite anti-dripping agent (Span20-lauric acid-LDHs) was synthesized by re-assemble method, and the resulting materials were fully characterized. The results showed that surface organophilic modification can improve surface tension of Span 20-lauric acid-LDHs and induced uniform dispersion of Span 20-lauric acid-LDHs in PVC matrix. In addition, Span20 has two types existing form: surface adsorption and interlayer intercalation, therefore, the surface hydrophilicity of film was improved markedly and the interfacial tension between water and film was decreased significantly by adding Span20-lauric acid-LDHs. In other words, anti-drop property of the film could be significantly improved. In addition, organic-inorganic composite anti-dripping agent can improve the insulation performance and visible light transmittance of films.更多还原