New routes to silicic acid containing inorganic-organic hybrid precursors and polymers

Abstract

In view of the outstanding role that silica acids (s. a.) play in inorganic materials a survey will be presented regarding the possibilities of the integration of s. a. in organic matrices via chemical reactions. The objective is to combine the advantageous properties of the silicic acid with those of the organic compounds in order to generate novel materials. The reactions of silicic acids with organic molecules, as studied by 29Si NMR spectroscopy, are described using the silici acid H8Si8O20 with a defined double four-ring structure as an example. By silylation of the hydrophilic H8Si8O20 its functional organophilic derivatives were synthesized. The s. a. derivatives with epoxy-, alkoxy- HSi-, ketoester or unsaturated groups are capable of condensation, polymerization, complexation or additive reactions leading to reactive inorganic-organic precursors or polymers with the defined dilicic acid unit. The synthesis and structure of the following s. a. containing precursors and polymers will be reported: (a) inorganic-organic polymers with a high content of silanol groups, (b) microporous polymers free of silanol groups and (c) metal (Al, Zr) alkoxide complexes attached to defined silicic acid units. The model reactions of the double four-ring silicic acid derivatives can be transferred to technical silicic acid solutions prepared from water glass. The presented reaction pathways are a basis for the preparation of a great variety of new inorganic-organic compounds with tailor-made structures and properties which can be used for highly homogeneous and stoichiometric materials.