Comparison of new periodic, mesoporous, hexylene-bridged polysilsesquioxanes with Pm3n symmetry versus sol-gel polymerized, hexylene-bridged gels

Hexylene-bridged polysilsesquioxanes were synthesized from 1,6-bis(triethoxysilyl)hexane (BESH) by acid- and base-catalyzed, sol-gel polymerizations and surfactant templating in order to compare, for the first time for any bridged polysilsesquioxane, the structures and porosities created by the different methods of preparation. Surfactant templating with Brij 56 under acidic conditions and N-(3-trimethyl-ammoniumpropyl)hexadecylammonium dibromide under basic conditions gave rise to the first periodic mesoporous hexylene-bridged polysilsesquioxanes ever reported. Both exhibited cubic Pm3n mesostructures with narrow pore size distributions (2.2 and 3.82 nm, respectively) and the highest surface areas ever reported for hexylene-bridged polysilsesquioxanes. Hexylene-bridged polysilsesquioxanes prepared under acidic, sol-gel conditions became non-porous during drying, but base-catalyzed sol-gel polymerizations of BESH afforded high surface area xerogels with pore size distributions comparable to periodic mesoporous organosilicas.