INVERSE ORGANIC-INORGANIC COMPOSITE-MATERIALS - HIGH GLASS CONTENT NON-SHRINKING SOL-GEL COMPOSITES

We, as well as others, have been interested in the sol-gel process for the synthesis of hybrid inorganic-organic composite materials. Since our first report on the application of tetraalkoxysilanes possessing p olymerizable alkoxides for the production of non-shrinking sol-gel com posites, we have extended our efforts towards increasing the glass con tent in these composite materials. The stoichiometry in the tetraalkox ysilanes limits the maximum glass content in the original non-shrinkin g composites to 10%-18%. In order to increase the glass content to gre ater than 50%, we focused our efforts on the use of silicic acid oligo mers. Molecular weights of the poly(silicic acid) materials were varie d from M(n) = 5000 to M(n) = 2 000000 by controlling reaction conditio ns. In addition, branching ratios (ie. linear vs. spherical particles) can be controlled by changing the catalysts used. The properties of t he resulting composite can range from a transparent flexible material to a transparent hard material simply by changing the organic polymer in the composite.