Sol-gel processing of polyhedral oligomeric silsesquioxanes : nanohybrid materials incorporating T8 and T10 cages

Polyhedral oligomeric silsesquioxanes (POSS, T8 and T10) have been incorporated in hybrid silica materials via hydrolysiscondensation of octa- and deca(triethoxysilylated)-POSS precursors, respectively. The precursors were synthesized via a thiol-ene Click reaction involving the corresponding octastyryl-T8 or decastyryl-T10 molecules and thiopropyltriethoxysilane. Following addition of water and HCl (as catalyst) to a solution of the precursors, gels were formed within a few minutes. The resulting hybrids were characterized by TEM, FTIR, N2 physisorption analyses, solid-state NMR (29Si and 13C), and TGA, which indicated that the T8 and T10 cages were incorporated and remained intact within the hybrid gel network, with no Si–C cleavage being observed via 29Si NMR. FTIR data indicated that water retained within the gels following drying and aging at ambient temperature exhibited an unusual “connective”, ice-like structure, suggesting that it is initially retained as a key component of the gel network during consolidation and aging at ambient temperature. Following aging, the water was readily removed by evacuation at 100 °C without significantly modifying the network structure, on the basis of the FTIR spectrum of the gel. To the best of our knowledge, this is the first report of the incorporation of T10 cages in such gels.