New highly cross-linked polysiloxanes were prepared by sol−gel polymerization of 1,6-bis(diethoxymethylsilyl)hexane (1) and 1,4-bis(diethoxymethylsilyl)benzene (2). Hydrolysis and condensation of 1 and 2 under acidic and basic conditions with 4 equiv of water led to the rapid formation of hexylene- and phenylene-bridged polysiloxane gels. The dry gels (xerogels) were intractable, insoluble materials that were noticeably hydrophobic, exhibiting no swelling in organic solvents or water. Most of the xerogels were high surface area, mesoporous materials. Hexylene-bridged polysiloxanes prepared under acidic conditions were always nonporous regardless of whether they were processed to afford xerogels or supercritically dried as aerogels. Hexylene-bridged polysiloxanes prepared under basic conditions and all of the phenylene-bridged polysiloxanes were mesoporous with surface areas as high as 1025 m2/g.

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Two new surfactant molecules are reported that contain thermally labile Diels-Alder adducts connecting the hydrophilic and hydrophobic sections of each molecule. The two surfactants possess identical hydrophobic dodecyl tail segments but have phenol and carboxylic acid hydrophilic headgroups, respectively. Deprotonation with potassium hydroxide affords the formation of water-soluble surfactants. Room temperature aqueous solutions of both surfactants exhibit classical surface-active agent behavior similar to common analagous alkylaryl surfactant molecules. Critical micelle concentrations have been determined for each surfactant through dynamic surface tension and dye solubilization techniques. Small-angle neutron scattering measurements of the aqueous surfactant solutions indicate the presence of spherical micelles with radii of 16.5 angstroms for the carboxylate and 18.8 angstroms for the phenolate. When these surfactants are exposed to elevated temperatures (>50 degrees C), the retro Diels-Alder reaction occurs, yielding hydrophilic and hydrophobic fragments. Aqueous solutions of each surfactant subsequently exhibit a loss of all surface-active behavior and the micellar aggregates are no longer detectable.