On the determination of Ostwald ripening rates from dynamic light scattering measurements

The Ostwald ripening rate of several alkane in water emulsions stabilized b y a nonionic surfactant is determined from dynamic light scattering (DLS) m easurements. With the aid of computer simulations, the intensity weighted d roplet radii obtained with DLS are converted to number averages, by taking the form of the droplet size distribution-which evolves continuously toward a stationary distribution-into account. Thereby the effect of the transiti on from an initial, log-normal size distribution toward its stationary form is included. Second a model is proposed to account for the effect of the f inite size of the surfactant layer (surrounding each oil droplet) on the me asured particle size and thus on the ripening rate. It is found that both t he effect of the transition from a nonstationary regime toward the stationa ry Lifshitz-Slyozov-Wagner regime and the effect of the finite size of the surfactant layer influence the ripening rates significantly.