Sol-gel processing of polyhedral oligomeric silsesquioxanes: nanohybrid materials incorporating T-8 and T-10 cages

摘要

Polyhedral oligomeric silsesquioxanes (POSS, T-8 and T-10) have been incorporated in hybrid silica materials via hydrolysis-condensation of octa- and deca(triethoxysilylated)-POSS precursors, respectively. The precursors were synthesized via a thiol-ene Click reaction involving the corresponding octastyryl-T-8 or decastyryl-T-10 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, N-2 physisorption analyses, solid-state NMR (Si-29 and C-13), and TGA, which indicated that the T-8 and T-10 cages were incorporated and remained intact within the hybrid gel network, with no Si-C cleavage being observed via Si-29 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 degrees 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 T-10 cages in such gels.