The Study On Synthesis And Application Of Mesoporous Silica With The Template Of Dendrimer

The pore size of mesoporous silica is equal and the pores are orderly arranged, the diameter of the pore size is between2and50nm. Also mesoporous silica is a new kind of inorganic nanometer materials with high surface area and high thermal stability, so it is widely applied in the areas of adsorption, separation and catalysis. Mesoporous silica is mainly prepared through the method of templating. Because of the limitations in the choice of current templates and the defects of templates, we can not precisely predict the pore structure, pore size and shape of mesoporous materials. And it is difficult to control the pore size and pore distribution of mesoporous silica. Therefore, in this paper we synthesized dendrimers (PAMAM) with different configurations. Then we prepared novel and controllable mesoporous silica with the template of PAMAM and name it DMS siries. Silane coupling agent including KH550, KH570and KH792was employed for modifying surface activity of DMS, to explore a novel strategy for developing mesoporous silica of high performance. Finally, Poly(lactic acid)(PLA) nanocomposites which is one of most important biodegradable materials, were prepared with DMS by solution blending.(1) Homogeneous DMS system In a typical synthesis of the mesoporous silica in this work, it was obtained by an HCl-catalyzed sol-gel process of hydrolysis of TEOS in a solution of PAMAM followed by the removal of the dendritic templates through water extraction. BET, TGA, NMR and HRTEM results confirmed that mesoporous silica materials with random pore, large surface area, excellent thermal stability, and narrow pore size distribution have been successfully synthesized. This artical researches for the best reaction condition for the preparation of DMS through changing the experiment condition to obtain the best ideal effect, the molar ratios of PAMAM/TEOS/HC1/H2O=2×10-4:0.02:0.2:5.6. As PAMAM is an amphiphilic substance with good solubility in water, the template could be effectively removed by water removal and the silica could remain more hydroxyl groups on surface. Ultimately, the recycle PAMAM dendrimer has rarely wasted and has good chemical stability could be reuse and recovery.(2) Multiple DMS system Michael addition and amidation was first used to synthesize different generations of PAMAM, then bromoalkane was used to produce hydrophil PAMAM. All types of templates were further used to synthesize DMS with different pore structure and silane coupling agent was grafting to pore surface of DMS. FTIR, TGA, SAXRD, BET and HRTEM results confirmed that, through choosing different types and generation could effectively control the DMS pore size. A series of functional mesoporous silica with various active functional groups were successfully synthesized through grafting reaction between silane coupling agent and Si-OH from DMS. But grafted coupling agent, the pore size, surface area, pore volume of DMS would be diminished and the pore size distribution would be broadened. (3) PLA/SiO2system PLA/SiO2nanocomposites which included PLA(3100D)/DMS, PLA(3100D)/nanoSiO2, PLA(305D)/DMS, were prepared by solution blending, and the foams using the supercritical carbon dioxide (ScCO2) foaming process were obtained. It is confirmed by DSC, DMA, TGA and SEM results that SiO2has good compatibility with PLA. The crystallization PLA type (3100D) system shows that the crystallization rate and Tg of nanocomposites decreased when SiO2mixed in PLA. For this phenomenon, PLA/DMS is more sensitive and clearer than PLA/SiO2. The insulations PLA type (305D) system shows PLA/DMS could be used to produce foaming material and the bubble size of holes is micron level. The SEM images of foaming materials showed the homodisperse of the cell size, and the bulk density of foams descreased by the addition of mesoporous silica.