Factors Controlling the Stability of a Kinetically Hindered Lamellar−Lamellar Transition

Abstract

We show that we can manipulate the stability of a metastable gel phase, either to enhance its transitory nature or to "lock" it in. Using simple additives such as salt and fatty alcohol we were able to examine both the long-range effect, acting between charged bilayers, and short-range effects on the metastability. We found that the addition of salt to the cationic surfactant diethanolamine ester dimethyl ammonium chloride destabilized the gel phase, and at high concentrations it was able to decrease the length of time taken for the gel phase to revert to a hydrated solid "coagel" phase by an order of magnitude. The growth of the coagel phase was also found to be affected by increasing salt concentration, changing from needle-like (1D) to spherical growth. In contrast to the marked destabilization of the gel phase by salt, the addition of 1-octadecanol was found to prolong the lifetime of the gel phase almost indefinitely by disrupting the short-range packing between the surfactant molecules. This suggests that counterion binding plays a major role in the stability of metastable lamellar gel phases.