Spatial patterns formed by growing TEOS polymers

2014 Silicon tetraethoxyde (TEOS) monomers are dissolved in a water/ethanol mixture. Through hydrolysis and condensation they aggregate to form branched siloxane polymers ; in a few hours these polymers build a gel throughout the solution. The patterns formed by the growing polymers are studied through small angle neutron scattering. In the reaction bath, these patterns result from repulsive interactions, whose range 03BE is controlled by the smaller polymers of the bath. In diluted solutions, the patterns give the size Rz of the largest polymers, which limits the connectivity of the reaction bath. As the polymers recombine, the connectivity length diverges, whereas the interaction length remains microscopic and keeps growing regardless of the gel point. This growth leaves the network with a set of selfsimilar heterogeneities similar to those found in many other gels. J. Physique 48 (1987) 2131-2137 DTCEMBRE 1987,