Preparation of Polyhedral Oligomeric Silsesquioxanes Containing Carboxyl Side-Chain Groups and Isolation of a Cage-Like Octamer Using Clay Mineral

The hydrolytic condensation of 3-(triethoxysilyl)propyl succinic anhydride (TESPSA) in water using bulky base or acid catalysts such as tetra-n-butylammonium hydroxide (n-Bu4NOH) or trifluoromethanesulfonic acid, respectively, afforded mixtures containing polyhedral oligomeric silsesquioxanes (POSSs) as main products. The mixture obtained under basic conditions contained cage-like octamer (T8-POSS) and that from acidic conditions contained cage-like decamer (T10-POSS) and dodecamer (T12-POSS). On the other hand, polysilsesquioxanes with number average molecular weights of 1.25 × 104 or 1.43 × 104 were obtained when the hydrolytic condensation of TESPSA was performed in the presence of non-bulky base (sodium hydroxide) or acid (hydrochloric acid) catalysts, respectively, in water as a solvent. In addition, only T8-POSS could be isolated from the silsesquioxane mixture obtained via the hydrolytic condensation of TESPSA using n-Bu4NOH by sequential treatment with a clay mineral such as montmorillonite in water and acetone.