Simple multiangle, multicorrelator depolarized dynamic light scattering apparatus

Dynamic light scattering is a powerful, noninvasive technique for the study of particles and macromolecules in solution. While commercial instruments are widely available, at any one time most of them can only measure the signal from a single detector positioned at a particular angle. For many systems, such as gels, solutions of nonspherical particles with dimensions exceeding about 100 nm, and polydisperse samples containing large components, proper characterization requires measurements at multiple angles. Such complete experiments are tedious, requiring the detector to be moved to each new angle. Even if the detector is motorized, the process is slow and this limits the study of evolving systems. To improve the situation, a multicorrelator apparatus for simultaneous multiple angle dynamic light scattering has been constructed. Provision is made for depolarized dynamic light scattering, and it is shown that in favorable cases a particle size can be obtained without prior knowledge of viscosity. Once that particle size is determined, the viscosity of the suspension can be measured. The instrument is well suited to the observation of kinetics of aggregation, growth, or gelation, but its utility is demonstrated with simple particulate systems. (c) 2006 American Institute of Physics.