In-situ catalyst generation and controlled hydrolysis in the sol-gel precipitation of zirconia and titania particles in poly(dimethylsiloxane)

The usual sol-gel hydrolysis-condensation technique for the in-situ generation of reinforcing silica particles within an elastomer was recently modified by (i) controlling the required water of hydrolysis by simply absorbing it from the air, and (ii) generating the required catalyst in-situ from a tin salt. In the case of the silica, which is generated in poly(dimethylsiloxane) (PDMS), the technique had the advantages of producing well dispersed, highly reinforcing particles that did not significantly reduce the transparency of the composite. Applying the new technique to the in-situ generation of zirconia and titania in the same polymer also gave small well-dispersed particles, good reinforcement, and improved thermal stability. Although transparency was not maintained as well as in the case of the controlled hydrolysis producing silica, it was definitely better than that of composites prepared by the usual excess water method.