Synthesis and Characterization of Polyhedral Silsesquioxanes Bearing Bulky Functionalized Substituents

A simple route to synthesize polyhedral silsesquioxanes, (RSiO 1.5 ) n, by the hydrolytic condensation of modified aminosilanes, is reported. The starting material was N -(β-aminoethyl)-γ-aminopropyltrimethoxysilane, a trifunctional aminosilane. It was reacted with a stoichiometric amount of phenylglycidyl ether in sealed ampules at 50 °C for 24 h, leading to the trisubstituted product plus a series of oligomers arising from the intermolecular reaction between methoxysilane groups and the secondary hydroxyls generated by the epoxy−amine reaction. When this product was subjected to hydrolytic condensation using a variety of catalysts (HCl, NaOH, HCOOH) and a thermal cycle attaining 150 °C, polyhedral silsesquioxanes (SSQO) were obtained. Their molar mass was independent of reaction conditions as revealed by size exclusion chromatography. Characterization by 1 H, 13 C, and 29 Si NMR suggested that the main product was a mixture of polyhedral SSQO with n = 8 and 10; i.e., T 8 and T 10 . Due to the high OH functionality, i.e., 24 OH groups in T 8 and 30 OH groups in T 10 polyhedra, the synthesized product may be used as a cross-linking unit of very high functionality or as a modifier for several polymeric materials.