Evaporation-induced self-assembly of mesoscopically ordered organic/organosilica nanocomposite thin films with photoluminescent properties and improved hardness

We report the use of evaporation-induced self-assembly (EISA) to organize and chemically bind a functionalized organic material, N,N′-bis(4-tert- butylphenyl)-N,N′-bis(4-((E)-2-(triethoxysilyl)vinyl)phenyl)biphenyl-4, 4′-diamine (3), into the ordered nanochannels within an organosilica matrix based on 1,2-bis(triethoxysilyl)ethane (BTSE). Characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and nitrogen absorption/desorption (BET) were used to show that the EISA derived thin films and powders are highly ordered with compound 3 occupying and chemically bound within the nanochannels. Furthermore, photoluminescent spectroscopy (PL) and nanoindentation show these materials have unique PL properties with hardness values twice of their nonordered counterparts. © 2008 American Chemical Society

Self-assembly, optical, and mechanical properties of surfactant-directed biphenyl-bridged periodic mesostructured organosilica films with molecular-scale periodicity in the pore walls

Self-assembly, optical, and mechanical properties of surfactant-directed biphenyl-bridged periodic mesoporous organosilica thin films (PMOF-Bp's) with molecular-scale periodicity in the pore walls were successfully demonstrated for the first time. The biphenyl-bridged organosilica precursor, 4,4-bis(triethoxysilyl)biphenyl (Bp-TES) has been used as the sole precursor (100%) for preparing PMOF-Bp films with molecular-scale periodicity in the pore walls via the surfactant-mediated one-step mild acidic self-assembly process. High-resolution X-ray diffraction (HRXRD) patterns and transmission electron microscope (TEM) images of PMOF-Bp materials confirmed the formation of a biphenylbridged periodic mesophase with molecular-scale periodicity in the organosilica framework. Fourier transform infrared (FT-IR) and NMR spectroscopic data also strongly suggested that the biphenyl organic segment is covalently bonded with silicon atoms in the acidic ethanol-washed biphenyl-bridged mesoporous framework. The emission behavior is sensitive to synthesis and thermal treatment temperatures. The biphenyl-bridged PMO films show absorption and emission due to the presence of biphenyl segment in pore walls. Nanoindentation hardness of the PMOF-Bp films could be controlled by temperature, degree of pore ordering and molecular periodicity, and even thickness of films. For example, well-organized PMOF-Bp film with molecular-scale periodicity in the pore walls showed a higher hardness value (0.23 GPa) than that of less mesoordered PMOF-Bp film (0.13 GPa). For all solvent-extracted PMO samples, N2 gas sorption experiments showed the surface area (from 714 to 688 m2/g), the pore volume (from 0.76 to 0.68 cm3/g), and pore size (2.81 to 3.1 run). The solid-state NMR and FT-IR spectroscopic data were used to propose plausible interpretations of the formation of hydrogen-bonded molecular periodicity in the pore walls. The experimental periodicity value 1.40 nm was strongly supported by the periodicity obtained by the structural model (1.389 nm). © 2009 American Chemical Society