化工学报2019，Vol.70Issue(5)：1663-1673,11.DOI:10.11949/j.issn.0438-1157.20180940
γ-巯丙基三乙氧基硅烷水解程度对纳米二氧化硅接枝机理影响的DFT研究
DFT study on effects of hydrolysis degrees of 3-mercaptopropyltriethoxysilane on grafting mechanisms of nano-silica
摘要
Abstract
In order to investigate the effects of hydrolysis degrees of 3-mercaptopropyltriethoxysilane (MPTS) on the grafting mechanisms of nano-silica, the grafting activities and grafting mechanisms of the hydrolyzed products in different degrees are systematically investigated based on density functional theory (DFT). The results show that the cluster model of nano-silica optimized by the GGA-PBE function is the most reasonable. The O atoms in surface silanols of nano-silica are the nucleophilic sites and the H atoms are the electrophilic sites. For MPTS and its hydrolyzed products, the O atoms are the nucleophilic sites and the Si atoms are the electrophilic sites. The LUMO orbitals shift to Si atoms and the HOMO orbitals to O atoms after hydrolysis. The electrophilic indexes of Si atoms and nucleophilic indexes of O atoms are all increased according to the Fukui function, indicating that the hydrolyzed products are more susceptible to be attacked by the surface silanols of nano-silica and the activities of grafting reaction are improved after hydrolysis. The active energies (Ea) of grafting reactions for M0—M3 follow the order of M0＞M3＞M1＞M2 (M0 is short for MPTS, M1, M2, M3 are short for the hydrolyzed products of first, second, and third order, respectively), the active energies are obviously reduced after hydrolysis. The grafting reactions of M0-M3 are SN2 nucleophilic substitution and exothermal reactions, but the mechanisms of the grafting reactions are quite different. For M0 — M2 the grafting reactions occur via the reaction channels of eliminating ethanol, but for M3 the grafting reaction occurs via the reaction channels of eliminating H2O. The steric hindrance and the electrophilicity of Si atoms have a significant effect on the grafting reactions of M0—M2.关键词
计算化学/二氧化硅/接枝反应/反应动力学/γ-巯丙基三乙氧基硅烷/水解程度Key words
computational chemistry/silica/grafting reaction/reaction kinetics/3-mercaptopropyltriethoxysilane/hydrolysis degrees分类
化学化工引用本文复制引用
尚志新,张香兰..γ-巯丙基三乙氧基硅烷水解程度对纳米二氧化硅接枝机理影响的DFT研究[J].化工学报,2019,70(5):1663-1673,11.基金项目
山西省科技重大专项(20111101060) （20111101060）
