Silica gels with tunable nanopores through templating of the L₃ phase

We describe a detailed synthesis of a silicified inorgaric/organic nanoporous monolithic composite conforming to the lyotropic liquid crystalline L₃ phase. The pore dimensions of the silicified L₃ phase scale with the solvent volume fraction in the synthesis reaction mixture. Changing the solvent fraction in the initial solution changes the ultimate pore diameter in the silicate, providing a simple method for tuning the diameter of the pores in the matrix. The resulting monolith is optically isotropic and transparent with a nonperiodic network. Accessible pores (which permeate the entire structure) in the silicified materials correlate with the solvent domain of the original liquid crystalline phase and therefore negate the need to remove the surfactant in order to gain access to the pore network. Measured characteristic dimensions are from 6 to well over 35 nm. X-ray scattering studies indicate a low polydispersity in the pore diameters for a given solvent fraction. Transmission electron and atomic force microscope images are consistent with a random morphology and measured surface areas exceed 960 m² g^-1 in extracted materials.