Synthesis of porous organosilicates in the presence of alkytrimethylammonium chlorides: Effect of the alkyl chain length

A series of organosilicates were prepared using 1,2-bis(trimethoxysilyl)eth ane (BTME) as silica precursor and alkyltrimethylammonium chloride (C(n)TMA Cl) surfactants with different chain lengths (n = 8, 10, 12, 14, 16, 18) as supramolecular templating materials. C-13 and Si-29 NMR data showed that a fter surfactant extraction, all samples consisted of pure organosilicate. A dditional characterization techniques, that is, XRD, N-2 adsorption, and SE M, were also used to gain insights into the structure, porosity, and morpho logy of the materials. These properties were found to be strongly dependent on the surfactant chain length and the preparation conditions. Materials p repared in the presence of surfactants with the shortest carbon chains were microporous akin to amorphous organosilicate xerogels. However, in the pre sence of long chain surfactants, periodic mesoporous organosilicates with n arrow pore size distributions occurred. The pore sizes of such materials we re found to increase with the surfactant carbon chain length. With only one exception, these materials exhibited two-dimensional hexagonal symmetry.