Aerogels, emulsions, and composites: Controlling structure with organic sol-gel chemistry.

摘要

The sol-gel polymerization of resorcinol with formaldehyde is a proven synthetic route for the formation of organic aerogels. These materials can also be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. Both resorcinol-formaldehyde and carbon aerogels are characterized by high porosity (50--98%), ultrafine cell/pore sizes (< 100 mn), high surface area (400--1000 m(sup 2)/g), and a solid matrix composed of interconnected colloidal-like particles or fibrous chains with characteristic diameters of 10 nm. While this nanostructure and the low Z (atomic number) composition are responsible for the unique optical, thermal, acoustic, mechanical, and electrical properties of organic aerogels, there are certain applications in which a larger scale structure is also desired in combination with the unique features of the aerogel. In order to achieve this goal, we have been emulsifying our resorcinol-formaldehyde sols to form foams which retain the aerogel framework but have some cells/pores as large as 2 (mu)m. In another approach, we have infused an emulsion-derived polystryene foam with a resorcinol-formaldehyde sol to form a new composite foam. This paper addresses the chemistry-structure-property relationships of organic aerogels, their emulsion-derived derivatives, and composite foams.