Experiments and modeling of growth of myelinic figures in Aerosol OT/water system

A quantitative penetration scan in a vertically oriented cell was used to determine behavior when water was brought into contact with neat Aerosol OT (AOT) at 30 °C. Myelinic figures developed having roots at the initial surface of contact between the phases and length proportional to the square root of time, in agreement with previous observations for AOT and other surfactants by various workers. However, the present experiments also included measurement of positions of the interfaces between lamellar and cubic and cubic and reverse hexagonal phases, which were also proportional to the square root of time. A similar experiment in which a thin layer of AOT was contacted with a large quantity of water was also conducted. A model is presented which includes both growth of myelinic figures and diffusion in the various liquid crystalline phases. With this model and data from the two experiments effective diffusion coefficients for all three liquid crystalline phases and the composition of the myelinic figures were calculated. The former were found to be of order 10−10 m2/s, the latter approximately 50 wt.% AOT.