| Abstract
| - Arylene-bridged polysilsesquioxanes are an interesting class of porous materials preparedby sol−gel processing of ethoxysilane monomers in which there are two or more trialkoxysilylgroups positioned about an arylene bridging group. The majority of these materials are highlyporous with surface areas as high as 1880 m2/g. In an effort to understand the nature ofporosity in these materials, small-angle X-ray and neutron scattering were employed tocharacterize phenylene-, biphenylene-, and terphenylene-bridged polysilsesquioxanes. Phenylene-bridged polysilsesquioxane xerogels and aerogels were also compared to understandthe effect of drying protocol on pore structure. The effect of catalyst concentration is alsoreported for the base-catalyzed system. In all cases studied here, we find evidence for domainsin the nanometer range with distinct fractal character. We associate these domains withporosity rather than microphase separation of organic and inorganic moieties. The natureof this porosity depends on the bridging group in a systematic way, but is only weaklydependent on other synthetic parameters such as catalyst type, catalyst concentration, anddrying protocol.
- Small-angle X-ray and neutron scattering are used to determine the morphology of porous xerogels and aerogels synthesized from arylene-bridged polysilsesquioxanes. In all cases studied here, we find evidence for domains in the nanometer range with distinct fractal character. The nature of this porosity depends on the bridging group in a systematic way, but is only weakly dependent on other synthetic parameters.
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