Combining Light Scattering and Small Angle X-ray Scattering for Particle Characterization*

Aqueous solutions of polystyrene microspheres (PS) of varying diameter (25nm – 490nm) were used as a test system of known size distribution to master a combined approach to particle characterization using Static Light Scattering (SLS) and Small Angle X-ray Scattering (SAXS), before applying the combined SLS/SAXS approach to studying polymeric microgels of similar sizes. SAXS is a scattering technique that can be used to determine the average size, shape, and internal structure of nanoparticles in solution. SLS can also be used to determine the size and shape distribution of particles, but SAXS probes systems over a wider range of scattering vectors (q). The higher q-range allows the examination of smaller particles, as well as portions of large particles, and elements of internal structure. Also, unlike light scattering, SAXS yields information on the internal structure of particles as X-rays penetrate many non-transparent materials and have enough resolution to probe small internal structural elements. By utilizing both methods we can learn more about the system of interest such as polymeric microgels and develop a more complete understanding of its internal structure. This presentation will highlight our successful use of combined SLS and SAXS (done with Xenocs Xeuss 3.0) in studying the test system of polystyrene microspheres. The preliminary SAXS results on polysaccharide microgels will also be presented together with an attempt to reconcile these SAXS results with the earlier multiangle SLS measurements on the same system.