AGGREGATION KINETICS OF OIL-IN-WATER MICROEMULSION DROPLETS STABILIZED BY C12E5

We have measured the kinetics of aggregation of oil-in-water microemulsion droplets stabilized by the nonionic surfactant n-dodecyl pentakis(ethylene glycol) ether (C12E5). The rate of droplet aggregation, which is induced by increasing temperature, was determined by using an iodine laser temperature-jump (ILTJ) technique. The second-order rate constant for the droplet aggregation is found to be significantly lower than the diffusion-controlled limiting value, indicating an energy barrier of magnitude several kT must be overcome before the equilibrium aggregated state is reached. This energy barrier is found to decrease with increasing droplet size.