Critical dynamics in the presence of a silica gel

Abstract

Dynamic and static light scattering results are reported for isobutyric acid and water in a 4 wt. % silica network with a crossover length of 300 \AA{}. In the one-phase region, well away from the critical point, the decay rate for order parameter fluctuations is unaffected by the network. Near the critical point, the order-parameter correlation function is well fitted by the sum of an exponential with decay rate ${\mathrm{\ensuremath{\Gamma}}}_{1}$ and a term of the form exp[ln(\ensuremath{\tau}/${\mathit{t}}_{0}$)/ln(${\mathrm{\ensuremath{\Gamma}}}_{2}$${\mathit{t}}_{0}$)${]}^{3}$, with ${\mathrm{\ensuremath{\Gamma}}}_{2}$\ensuremath{\simeq}${\mathrm{\ensuremath{\Gamma}}}_{1}$. When the system reaches conditions where the correlation length of the pure system is \ensuremath{\sim}100 \AA{}, it spontaneously orders.