Photoactive perylenediimide-bridged silsesquioxane functionalized periodic mesoporous organosilica thin films (PMO-SBA15): synthesis, self-assembly, and photoluminescent and enhanced mechanical properties.

Well-organized periodic mesoporous organosilica thin films (designated as PMO-SBA15), having covalently bonded perylene-bridged silesquioxane (PTCDBS) inside their pore channels, are successfully synthesized via sol-gel self-assembly of 1,2-bis(triethoxysilyl)ethane and perylene-bridged silsesquioxane, using micelles of pluronic surfactant (P123) as a template for the first time. The surfactant is successfully removed from the pore channels of PMO-SBA15 by an acidic solvent extraction procedure. The final PMO-SBA15 thin films are characterized by high resolution X-ray diffraction (HRXRD), transmission electron microcopy (TEM), solid-state 29Si and 13C NMR CP/MAS NMR spectroscopy, nitrogen adsorption-desorption measurements, photoluminescence (PL) spectroscopy, and nanoindentation. HRXRD data reveal the formation of well-organized hexagonal channels in the pure PMO-SBA15 films. The intensity of the diffracted X-ray, however, systematically attenuates after incorporation of the perylene functionality inside the hexagonal channels. This is attributed to the low X-ray scattering contrast between the mesostructured organosilica walls and organic moieties (perylene) inside the channels, suggesting the successful incorporation of the photoactive perylene molecules inside the nanochannels. This was further confirmed by photoluminescence spectroscopy and nitrogen adsorption-desorption measurements. Additionally, the mechanical hardness of the functionalized PMO-SBA15 thin films, measured by nanoindentation, is significantly enhanced as compared with that of the pure PMO film. Thermogravimetric analysis (TGA) and elemental analysis suggested the functionalized PMO-SBA15 materials with PTCDBS.