Influence of the nature of the catalyst on the textural properties of organosilsesquioxane materials

The hydrolytic sol-gel polymerization of molecular organosilicon precursors with a 'rigid' geometry 1,4-C6H4[Si(OMe)(3)](2) (1) and a 'flexible' geome try 1,4-C6H4[CH2CH2Si(OMe)(3)](2) (2) was investigated varying the nature o f the catalyst. They were hydrolyzed under nucleophilic catalysis using non -ionic species such as dimethylformamide (DMF), dimethylaminopyridine (DMAP ), N-methylimidazole (NMI) and hexamethylphosphorotriamide (HMPT) in THF. T he effect of the concentrations of both the precursor and the catalyst was studied. Molecular precursor 1 led always to hydrophobic solids with degree s of condensation lying in the range 55-67%. These solids were mainly micro porous exhibiting high specific surface areas. The densities lay in the ran ge 1.37-1.42 g cm(-3). By contrast, the precursor 2 led to hydrophobic soli ds with no significant specific surface area. Degrees of condensation range d between 59 and 74% and the densities between 1.27 and 1.31 g cm(-3). The nature of the catalyst (ionic or non-ionic) involved in the hydrolytic sol- gel polymerization of molecular organosilicon precursors appeared to be of great influence on the textural properties of the resulting solids. (C) 200 0 Elsevier Science Ltd All rights reserved.