Imaging aerogels at the molecular level

Aerogels are a special class of open-cell foams that have an ultrafine cell/pore size (<50 nm), high surface area (400–1000 m² g^–1), and an ultrastructure composed of interconnected colloidal-like particles or polymeric chains with characteristic dimensions of 10 nm. The purpose of this paper is to directly image a series of resorcinol-formaldehyde (RF) and silica aerogels by high resolution transmission electron microscopy (HRTEM). A new vertical replication technique allows us to examine aerogels at the molecular level in situ so that differences in polymeric and colloidal aerogels can be visualized. Such information is crucial for nano-engineering the structure and properties of these novel materials.