Elastomeric organosilicon micronetworks

Trifunctional methyltrimethoxysilane and bifunctional dimethyldimethoxysilane monomers were cocondensed in water in the presence of surfactant. Strictly spherical micronetworks of narrow size distribution were obtained for particle sizes 10 nm < R < 30 nm. By special ''endcapping'' reactions all reactive SiOH groups were removed quantitatively, and the resulting micronetworks become soluble in common organic solvents like toluene, THF, or chloroform. For contents of trifunctional monomer larger than 50 mol % the particles do not swell irrespective of the choice of the solvent, whereas for lower mole fractions of trimethoxysilane an increasing swelling ratio is observed. Below 2.5 mol % trifunctional monomer the reaction within a microparticle remains subcritical and nonspherical, branched molecules are obtained. Subsequent addition of the bi- and trifunctional units leads to a micronetwork topology with different physical properties as compared to the simultaneously cocondensed one at identical overall particle composition. For instance, at 57 mol % trifunctional monomer content the ''homogeneously'' cross-linked microgel exhibits no glass transition before decomposition whereas the core-shell particle with linear chains in the core shows a weak glass transition at T-g = -107 degrees C.