【作者】 周宁琳；

【导师】 王延儒；

【作者基本信息】 南京工业大学 ， 纳米与界面化学工程， 2003， 博士

【摘要】 聚二甲基硅氧烷作为一种特殊性能的弹性体，具有优异的耐热性、耐寒性和电绝缘性，以及低表面能、低毒以及很好的光学透明性等性能，广泛应用于密封制品和电绝缘制品。但聚二甲基硅氧烷分子链之间作用力很小，生胶单独硫化后力学性能差，需要补强填料来增强。现在主要用气相二氧化硅来增强，但这种气相二氧化硅价格较贵，不易均匀分散在聚合物基体中。 聚合物／层状硅酸盐纳米复合材料是一种新型的有机无机杂化材料，这种材料由于实现了无机纳米相的均匀分散，所以一般只需很少量的层状硅酸盐就可以大幅度提高复合材料的各种性能，如力学性能、模量、热变形温度、对气体、溶剂等的阻隔性、热稳定性、延迟火焰生成以及光学性能、电性能等。因此，此类高性能、低成本的纳米复合材料引起人们的极大关注。 本论文首先根据聚二甲基硅氧烷分子结构的特点，设计合成了两类反应性插层剂十八烷基二甲基-3-三烷氧基硅丙基氯化铵(TPAC)、2-甲基丙烯酰氧乙基二甲基-3-三烷氧基硅丙基氯化铵(TPAB)，对钠基蒙脱土进行了有机化处理，进而制备了两类新型的蒙脱土纳米中间体，通过F7IR、XRD、SEM、TGA研究了不同类型、不同质量的插层剂改性的层状硅酸盐的性能，以了解插层反应的机理和特性；在小试的基础上进行了中试放大，通过对原材料的选择、配方的设计和调整合成了系列蒙脱土纳米中间体，并探讨了合成工艺。 采用不同的聚合方法(原位聚合、聚合物溶液插入法)合成了一系列不同结构、不同分子量的新型聚二甲基硅氧烷(PDMS)／蒙脱土纳米复合材料(剥离型)；通过FTIR、XRD、TEM、SEM对两种方法制得的复合材料进行了结构和性能的表征，以了解反应的机理和特征以及蒙脱土纳米中间体在聚二甲基硅氧烷基体中的剥离、分散情况；通过力学性能和动态力学性能(DMA)的测试了解层状硅酸盐微观纳米结构对材料宏观性能的影响；通过TGA研究了纳米复合材料的耐热性能；通过耐溶剂性能的测试研究了纳米片层对材料阻隔性能提高所起的作用；并在以上工作的基础上提出了纳米复合材料的作用机理和结构模型。 研究结果表明，原位聚合只能提高复合材料的伸长率，而溶液法只需很少量的改性层状硅酸盐就可以大幅度提高复合材料的各种性能，如力学性能、模量、中文摘要耐热性和耐溶剂性能等，可以同时达到增强、增韧的目的。对于低分子量的PDMS，溶液插入法在MMT-TPAC含量为2%时力学性能最好;对于较高分子量的PDMS，MMT-TPAC含量则在4%时体系达到最佳的增强、增韧效果(拉伸强度可提高223一305%，断裂伸长率可提高169%一286%);其力学性能远高于插层型的纳米复合材料和用传统气相5102填充的体系。PDMS从MT-TPAC初始分解温度随有机蒙脱土含量的增加而逐步增加，初始分解温度最高可以提高65℃。和PDMS相比，在分散的纳米复合材料中，溶剂的吸收率明显地降低，含有2%MMT一TPAC的PDMS溶剂的吸收率可下降27.5%，当MMT一TPAC的量接近2%时，吸收溶剂的下降趋势开始停止。 聚硅氧烷与烯类单体通过接枝共聚的方法是改进聚硅氧烷的物理机械性能的有效手段。此方法生产工艺简单，得到的改性硅橡胶具有较高的力学性能，但接枝后共聚物的耐热性明显下降，这一难题始终没有得到很好的解决。我们通过聚合物/层状硅酸盐纳米复合的改性方法，合成了一系列新型的剥离型接枝聚二甲基硅氧烷/蒙脱土纳米复合材料;在使接枝共聚物力学性能得到进一步改善的基础上，显著提高了接枝共聚物的耐热性(初始分解温度最高可以提高47℃)，同时纳米复合材料的耐油、耐溶剂性能也得到了进一步的提高，从而使此类复合材料具有更加广阔的应用前景。 利用现代分析仪器(FTIR、XRD、DMA、)以及力学性能等方法对其结构和性能进行了表征，_以了解在复杂体系中聚合物/勃土纳米复合材料的反应机理和特征;通过TGA研究了不同接枝型PDMs/蒙脱土纳米复合材料的耐热性能;通过耐油、耐溶剂试验了解各种介质和接枝型PDMS/蒙脱土纳米复合材料的作用机理;制备出一系列高强度、可室温固化且能够在较宽的温度范围下工作的耐油-接枝PDMS/蒙脱土纳米复合材料。 聚合物/豁土插层复合不但是制备高性能复食材料的有效手段，也是制备功能性材料的有效手段。我们将此新技术和稀土发光材料相结合，合成出新型的、具有发光性能的聚二甲基硅氧烷/蒙脱土纳米复合功能材料。 通过分子设计合成了一系列新型的功能稀土配合物，此类功能稀土配合物比相应稀土配合物的相对发光强度提高1360%(614nln)、1447%(591.5nm);以此为插层剂插入蒙脱土层间，合成了新型的功能稀土配合物/蒙脱土纳米中间体;南京工业大学博士论文这种特殊的插层剂不仅能起到撑开蒙脱土层间距的作用，而且还可使听合成的这类稀土纳米发光中间体以纳米级分散至聚二甲基硅氧烷基体中，解决了小分子配合物在聚合物基体中难以达到纳米分散且耐光性差、发光效率低等问题。在此基础上合成的PDMS一功能稀土配合物/勃土纳米复合材料不仅发光强度大幅度提高 (614nm提高255%、519nm提高268%)，并能达到高效地将不同波段的紫外光 (254nln、280nm、330更多还原

【Abstract】 Polydimethylsiloxanes (PDMS) are an unique class of polymers that can be crosslinked to form elastomers with many attractive properties, including low surface energy, low toxicity, high optical transparency, and good chemical and thermal stabilities. They have been extensively used in electrical-insulating products, sealing products as well. Most polydimethylsiloxanes today are reinforced with inorganic fillers because of the weak linkages between PDMS molecules. One of the main fillers, aerosilica, with smaller particle size, is easy to aggregate and is difficult to disperse in the silicone rubber matrix.Polymer-layered silicate nanocomposites represent a new class of organic /inorganic hybrid materials, where the inorganic fillers are dispersed into the polymer matrix on a nanoscale. These materials contain a relatively low amount of the layered silicate and often tend to exhibit superior physical and mechanical properties as compared to the corresponding pure polymer. Such improved properties include high strength, high modulus, high heat distortion temperature, increased barrier to gas and solvents, increased flame resistance, as well as electronic and optical properties, and make these materials attractive for a number of applications, especially due to the low cost of the nanofiller, and the small amounts required.In this works, two novel classes of organic agents , [3-(trialkoxysilyl) propyloctadecyl dimethylammonium chloride ( TPAC) and 2-(Methacryloyloxy)ethyl-dimethyl [3-(trialkoxysilyl) propyl] ammonium chloride (TPAB) were prepared and used as swelling agents to treat Na-montmorillonite (Na-MMT) for forming organoclays. This two kinds of organoclay were characterized by X-ray diffraction (XRD ), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The preparation process and the technical conditions of organo-MMT were studied and optimized.A series of novel exfoliated PDMS / MMT nanocomposite with different structures and properties were synthesized by using PDMS and different organoclays. The methods are in-situ polymerization and intercalated polymerization. The resultsABSTRACTindicate that there are very good compatibilities between MMT and PDMS. Nanoscale silicate dispersion was analyzed by FT-IR, XRD, SEM and transmission electron microscopy (TEM). Mechanical properties and dynamic mechanical analysis( DMA) were measured to assess reinforcement, Solvent uptake analyses were used to evaluate PDMS /silicate interactions and the extent of cure. TGA was also used to measure the thermal stability.It was shown that, the MMT-TPAC in PDMS matrix can increase not only the toughness but also the strength and modulus of PDMS to a great extent. The results proved that the nanometer-scale silicate layers of MMT-TPAC were completely exfoliated in PDMS matrix in the cases of 1 %, 2%, 4 % and 10%. In PDMS / MMT-TPAC system, the physical and mechanical properties reach the maximum value when volume percent of MMT-TPAC is 4% with high-MW PDMS aind volume percent of MMT-TPAC is 2% with low-MW PDMS. The nanocomposites exhibit markedly improved physical mechanical properties as compared with the pure polymer or conventional aerosilica-filled polymer composites. A 223 ~ 305%increase in the tensile strength and a 169% ~ 286%increase in the elongation were found for PDMS/MMT-TPAC as compared to that of pure PDMS. The reinforcing and intercalating mechanism of silicate layers in matrix were discussed. In addition, when the content of MMT-TPAC is 2%, the solvent uptake of PDMS reduces obviously.PDMS grafted by alkene monomers can increase physical mechanical properties of PDMS , but decreased the thermal stability of PDMS. This difficult problem was not solved yet.Two kinds of copolymers PDMS- g - (Methyl methacrylate) MMA and PDMS-g- MMA- acrylonitrile (AN) were prepared using graft copolymers synthetic approaches. A series of novel exfoliated graft PDMS / MMT nanocomposite has been synthesized by graft PDMS an更多还原