title: Self-assembly, optical, and mechanical properties of surfactant-directed biphenyl-bridged periodic mesostructured organosilica films with molecular-scale periodicity in the pore walls.
abstract: 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 biphenyl-bridged 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, N(2) gas sorption experiments showed the surface area (from 714 to 688 m(2)/g), the pore volume (from 0.76 to 0.68 cm(3)/g), and pore size (2.81 to 3.1 nm). 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).
authors.affiliation: Department of Materials Synthesis and Integration, Institute of Materials Research and Engineering (IMRE), The Agency for Science, Technology, and Research (A*STAR), 3 Research Link, Singapore 117602, Republic of Singapore. a-wahab@imre.a-star.edu.sg
authors.forename: M Abdul
authors.initials: MA
authors.lastname: Wahab
authors.forename: Chaobin
authors.initials: C
authors.lastname: He
mesh_terms: D001713:Biphenyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D055620:Optical Phenomena; D017646:Organosilicon Compounds / Q000737:chemistry*; D010316:Particle Size; D016062:Porosity; D012821:Silanes / Q000138:chemical synthesis / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: C535258:4,4-bis(triethoxysilyl)biphenyl; D001713:Biphenyl Compounds; D005782:Gels; D008567:Membranes, Artificial; D017646:Organosilicon Compounds; D012821:Silanes; D013501:Surface-Active Agents