Controlled polymerisation of silicic acids derived from mineral silicates. Part 3.— formation and reactions of QxMy(O1/2R)z
The preparation of reactive intermediates, of the type QxMy(O1/2R)z(where Q = SiO4/2; M = Me3SiO1/2; R = Et), has been studied. The intermediates (partially trimethylsilylated silicic acid esters) have been characterised and average structures have been determined. The formation and stability, and hence reactivity, of the intermediates, have been studied with respect to inter- or intra-molecular condensations under various reaction conditions: temperature, acidity and phase-transfer agent. The stability of the intermediates has been attributed to the formation of micelles in solution. The intermediates have been shown to undergo condensations with silicic acids from another source, e.g. a silicate mineral, yielding higher-molecular-weight polyorganosiloxanes. The intermediates have also been shown to react with various heteromolecules, yielding polymers which contain aluminium, phosphate, silicones, tetraethylsilicate, ethylenediaminetetraacetic acid and phenol groups.