Spin-coated periodic mesoporous organosilica thin films with molecular-scale order within the organosilica wall

Periodic mesoporous organosilica (PMO) thin films with long-range molecular order within the organosilica framework have been successfully prepared by spin-coating a solution of 1,4-bis(triethoxysilyl)benzene (BTEB), water, ethanol, HCl, and cetyltrimethylammonium bromide (CTAB) on silicon substrates. Powder XRD patterns of these thin films reveal the presence of a hexagonal phase mesostructure as well as ordered molecular-scale structure. The strong high-angle diffraction peaks indicate the longrange molecular order within the organosilica framework. The degree of organosilica condensation is relatively low, and hydroxyl groups formed in the hydrolysis reaction link the BTEB precursor molecules together in an end-to-end fashion via hydrogen bonding. Infrared spectra of these thin films suggest that the PMO films contain a significant number of hydroxyl groups in a hydrogen bonding environment with a peak at 3200 cm(-1). Results from the Si-29 magic-angle spinning (MAS) NMR spectroscopy provide additional evidence of the lower degree of organosilica condensation in these PMO thin films. High-resolution transmission electron microscopy (TEM) images reveal both the presence of mesopores and lattice fringes from the ordered packing of the hydrolyzed precursor molecules. The interior wall silanol groups are accessible, and their conversion into Si-O-Si(CH3)(3) groups has been demonstrated.