COLLOIDAL VS POLYMERIC AEROGELS - STRUCTURE AND VIBRATIONAL-MODES

Aerogels with very different structures can be obtained by varying the physicochemical conditions of preparation. The size of the elementary particles, the fractal dimension, and the average size of the fractal clusters strongly depend on the chemistry of the sol-gel process. The two extreme situations correspond to either a colloidal or a polymeric structure. These structural differences can be derived by comparing transmission electron microscopy and small-angle neutron scattering data from a broad set of materials. Some implications of these structural differences on the vibrational dynamics, investigated by inelastic light scattering, are discussed.