cles until a magnetic field is applied to align the spins in Commercially available latex particles with superparamagnetic the superparamagnetic inclusions. Then a strong, dipolar ininclusions have been characterized by polarized and depolarized teraction develops and the MLP form linear aggregates, large dynamic light scattering. The particles are spherical, but the larger enough to be seen in an optical microscope, that are readily ones (R g Ç 0.1 mm) with many magnetic inclusions behave in pulled toward the magnet. This ''chaining'' interaction, and dynamic light scattering experiments like symmetric tops while indeed all effects of an applied magnetic field (2-4), are the smaller particles do not. The as-received materials had a broad beyond the scope of the present study. In fact, it is the optical size distribution, but more narrowly distributed particles were preanisotropy of the magnetite inclusions that is important here.
pared by selective filtration for use in probe diffusion and stability
Optically anisotropic colloids are appealing choices for studies. The interaction of these negatively charged particles with ''probe diffusion '' experiments (5-20) where the motion a linear polyelectrolyte, negatively charged sodium polystyrene sulfonate, was studied by static and dynamic light scattering. De-of a particle is monitored to assess the local structure of some polarized dynamic light scattering is particularly sensitive to complex polymeric matrix, such as an entangled solution or changes in the stability of the colloids or interaction with the gel. These studies are commonly performed by dynamic light polyelectrolyte. The polyelectrolyte can prevent or reverse saltscattering, and one of the complexities is scattering arising induced aggregation of the superparamagnetic latex particles. Flufrom the matrix itself. The scattering from most polymer orescence photobleaching recovery experiments to monitor the momatrices is almost completely excluded in depolarized light bility of fluorescently labeled polyelectrolyte suggest that it is not scattering studies using a strongly depolarizing probe partibound to the latex particles; apparently, a mechanism other than cle. This advantage is particularly appealing in aqueous solusteric stabilization is involved. The dependence of the diffusion of tions where it is not possible to match the index of refraction the superparamagnetic latex particles upon added salt is discussed of the solvent and matrix component. Although the MLP in terms of the ion atmosphere surrounding the polyelectrolyte.
are fairly large probes, their rotational motion could provide