Lucent Technologies Inc.

Jorge Sanchez

Jorge L Valdes

Michael J Cauda

An aqueous dispersion of silica particles is mixed with a dialkyldialkoxysilane monomer, e.g., dimethyldiethoxysilane (DMDES), typically under basic conditions. Optionally, the monomer, or a portion thereof, is partially reacted prior to mixing, such that it is possible for a polydialkylsiloxane oligomer, e.g., polydimethylsiloxane (PDMS), to be added either with or instead of the monomer. The addition of the monomer (or oligomer) induces gelation of the silica. The contemplated mechanism is that the silanol groups on the growing polydialkylsiloxane chains are able to condense with silanol groups found on the silica particle surfaces, thereby anchoring the chains to the particles. These chains appear to have the ability to form bridges between particles and/or loops on individual particles. Such bridges appear to initiate formation of a silica particle network, and both the bridges and loops increase the silica particles' hydrophobicity. Both of these features contribute to gelation of the silica particles, substantially independent of the particles' surface charge.

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Geneva, Switzerland

Jorge Sanchez