Kinetic pathways of multiphase surfactant systems
Relaxation following a temperature quench of two- (L(alpha) and L3) and three-phase (L(alpha), L3, and L1) samples has been studied in a sodium dodecyl sulfate-octanol-brine system. In the three-phase case we have observed samples that are initially mainly of the sponge phase, with lamellar and micellar phases on the top and bottom of the sample, respectively. Upon decreasing the temperature, most of the volume of the sponge phase is replaced by the lamellar phase. During equilibration we have observed three regimes of behavior within the sponge phase: (i) first there is disruption in the L3 texture, then (ii) after the sponge phase homogenizes there is a L(alpha) nucleation regime; finally (iii), a bizarre plume connects the L(alpha) phase with the L1 phase. The relaxation of the two-phase sample proceeds instead in two stages. First L(alpha) drops nucleate in L3, forming an onion "gel" structure. Over time the L(alpha) structure compacts while equilibrating into a two-phase L(alpha)-L3 sample. We offer possible explanations for some of these observations in the context of a general theory for phase kinetics in systems with one fast composition variable and one slow.
Buchanan
M
Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom.
Starrs
L
Egelhaaf
SU
Cates
ME