This second lecture introduced us to a less explored area of research into the synthesis of materials by soft chemistry. Non-hydrolytic polycondensation processes can be used to generate a wide variety of metal oxides in non-aqueous media. The condensation reactions involved generate metal-oxygen-metal bridges, but it is the organic solvent that is the source of oxygen and not water as in the more conventional polycondensation reactions presented in the previous lesson.
Historical analysis of this subject shows that these methods were initiated in the first part of the twentieth century (1928-1955), but that a strong revival of interest associated with highly relevant developments in the field of nanomaterial synthesis took place under the impetus of French and then German teams between 1992 and 2000.
These synthesis methods, commonly referred to as "water-free" sol-gel processes, are generally carried out at higher temperatures (100°C-200°C), using thermal energy to react the organic components that generate the oxolation reactions. These non-hydrolytic syntheses are generally classified according to the nature of the leaving group (removal of ether, ester, alkyl halide, enolate, benzylacetamide...). In the simplest cases, we have presented the mechanisms for the formation of the first oxometallic species and the associated organic leaving groups. We have also illustrated the subject extensively by presenting numerous examples of gels and nanocrystals obtained by these processes, and their physical properties, which are of particular interest in the fields of catalysis, photocatalysis, nanophotonics, nanoionics...
