Some recent developments of polysilsesquioxanes chemistry for material science

This review is focused on a new class of materials, the Monophasic Organic-Inorganic Hybrid Materials (MOIHM). These solids correspond to a unique phase prepared from a molecular precursor using the hydrolytic polycondensation which is used in the sol-gel preparation of oxides from alkoxides precursors. In these materials, the oxide matrix is elaborated around the organic moiety, and covalent bonds (mainly SiC bonds) link together the oxide matrix and the organic part. These solids are metastable solids of which their formation is kinetically controlled: all parameters able to modify the kinetics of the hydrolysis polycondensation process are of importance for both the physical and chemical properties of the solids, The organic moieties are also a main factor in both the short range organisation and the texture of the solid: weak interactions are able to control the solid formation and a substructure between the organic units can be evidenced in the case of thienyl units from polymerisation in the solid state. These materials are also a convenient way for the introduction of physical properties in the oxide matrix. (C) 1998 Elsevier Science S.A. All rights reserved.