助表面活性剂对介孔二氧化硅孔径的影响

在十六烷基三甲基溴化铵(CTAB)与硝酸形成的胶束体系中,分别加入正戊醇与正辛胺作助表面活性剂,合成出介孔二氧化硅.经小角XRD和N₂气体吸附与脱附实验证实,随着CTAB与正戊醇摩尔比的增加,介孔二氧化硅的孔径增加;而随CTAB与正辛胺摩尔比的增加,介孔二氧化硅的孔径减小.主要原因是正戊醇增大了CTAB胶束体积,从而导致介孔二氧化硅的孔径增加.而在CTAB与正辛胺的混合胶束中,正辛胺同硅酸盐作用力比CTAB强,导致介孔二氧化硅的孔径减小.

Effect of Cosurfactants on Pore Size of Mesoporous Silica

Mesoporous silica was synthesized and templated by mixed micelles of cetyltrimethylammonium bromide(CTAB), n pentanol or n octylamine and nitric acid. The products were determined by small angle X ray diffraction and N 2 gas adsorption desoption. The results show that pore size of mesoporous silica increased with increase of the molar ratio of CTAB to pentanol, while the pore size decreased with increase of the molar ratio of CTAB to n octylamine. The reason is that micelle volume increased by addition of pentanol, resulting in the increase of the pore size of mesoporous silica, templated by the mixed micelles of CTAB, pentanol and nitric acid. However, there is bigger interaction between n octylamin and silicate than that between CTAB and silicate in the mixed micelles of CTAB, n octylamine and nitric acid, resulting in the decrease of the pore size of mesoporous silica.