4. Gels

The term "gel" covers several possible definitions. The gels in question here are, at the time of synthesis, polymeric semi-solids whose nanometer-sized pores are filled with the solvent in which they were created . However, the term "gel" also applies to these same materials, which have been dried in such a way that the initially liquid-saturated pores are now freed and filled with air. It will then be necessary to specify whether we are talking about fresh gels (often referred...