Abstract
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 1 cm2 silicon substrates. Powder XRD patterns of these thin films reveal the presence of a hexagonal phase mesostructure as well as highly ordered molecular scale structure. The strong diffraction peaks at 8.8, 17.6, and 26.6° 2θ identify the long-range molecular order within the organosilica framework. The mesostructure and molecular scale order can be preserved upon solvent extraction to remove the CTAB surfactant template. The degree of silica 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. This gives rise to the observed shift in the positions of the XRD peaks to slightly lower angles, as compared to the fully condensed state. FT-IR 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. High-resolution TEM images reveal both the presence of mesopores and lattice fringes from the ordered packing of the hydrolyzed precursor molecules. Results from the 29Si-NMR will also be presented to provide additional evidence of the lower degree of organosilica condensation in these PMO thin films. This is the first time in which PMO thin films with both hexagonal mesostructure and high molecular scale order have been successfully prepared.