FORMATION AND CHARACTERIZATION OF NOVEL ORGANODISILICATE GLASSES

Novel organodisilicate xerogel glasses have been prepared through sol-gel processing of several organo-bridged hexachlorodisilane compounds, namely, p-(Cl3SiCH2)(2)C6H4, 1,4-(Cl-3-SiCH2)(2)-2,5-Me(2)C(6)H(2), 1,4-(Cl-3-SiCH2)(2)-2,3,5,6-Me(4)C(6), and 9,10-(Cl3SiCH2)(2)-anthracene. These new xerogels have been characterized by SEM, thermal analysis (TGA), nitrogen sorption measurement, and solid-state C-13 and Si-29 NMR spectroscopy, All of the materials are stable up to about 430 degrees C. The xerogels from p-(Cl3SiCH2)(2)C6H4 have high surface areas with the bulk of the pore sizes being less than 50 Angstrom. Xerogels derived from the precursor 1,4-(Cl3SiCH2)(2)-2,3,5,6-Me(4)C(6) are only slightly porous with low surface areas, while those from 1,4-(Cl3SiCH2)(2)-2,5-Me(2)C(6)H(2) and 9,10-(Cl3SiCH2)(2)-anthracene are nonporous, Low or complete absence of porosity in xerogels with more sterically hindering organic bridges may be associated with a high percentage of fully uncondensed silicon sites, The Si-29 NMR results show that the degree of condensation ranges from 55 to 75%, and decreases markedly with increased size of the organic group.