Contrast Variation and optical polydispersity in colloidal suspensions

BANCHIO, A. J.; NÄGELE, G.; FERRANTE, A.; KLEIN, R.

PROGRESS IN POLYMER SCIENCE

Springer

Año: 1998 vol. 110 p. 54 - 60

0340-255X

  We present theoretical results on the effect of refractive index variations on static and dynamic light scattering in strongly correlated charge-stabilized suspensions which are optically and size polydisperse. The equilibrium microstructure and the short-time dynamics of these systems are calculated using a HNC integral equation scheme, and a coreshell model of optical polydispersity is discussed. Our calculations show that, close to an index matching point, the scattered intensity I(k), the measurable structure factor SM(k), and the measurable hydrodynamic function HM(k) become very sensitive to the refractive index contrast with respect to the solvent. Various definitions of index matching points are considered. The incoherent part of the scattered intensity is particularly strong close to these points. The anomalous behaviour of I(k) and H M(k) in the corresponding range of the solvent refractive index can be semi-quantitatively described by a simple approximative scheme. Consequences for scattering experiments aimed to determine size distributions or structural properties near index matching are discussed.