Three Different Sizes Obtained Using Light Scattering Techniques

The average scattered intensity is determined by the optical characteristics of particles in dispersion. The normalized time auto-correlation function of the scattered light intensity g (τ ) includes both the optical and hydrodynamic information of particles. From the different characteristics of particles, the particle sizes can be obtained. In this paper, three sizes: the static radius Rs, the hydrodynamic radius Rh and the apparent hydrodynamic radius Rh,app are discussed using dilute water dispersions of homogenous spherical particles poly(N-isopropylacrylamide) microgels, with a simple assumption that the hydrodynamic radius is in proportion to the static radius, when Rayleigh-Gans-Debye approximation is valid. Our results show that the difference between the mean static radii and the apparent hydrodynamic radii is large and the difference between the mean hydrodynamic radii and the apparent hydrodynamic radii is influenced by the particle size distribution.