Collect. Czech. Chem. Commun. 1993, 58, 2272-2281

Optics of Heterogeneous Media. Comparison of Some Light Scattering Model Calculations

Jaroslav Holoubek

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague, Czech Republic


Typical dependences of turbidity as a function of diameter of scattering elements and their volume fractions as well as a function of the wavelength of the incident light were calculated, based both on the Lorenz-Mie theory and the fluctuation theory of Debye and Bueche. Such dependences calculated for the polyethylene, polypropylene and polyamide inclusions differing slightly in their reactive index from the surrounding matrix of the same material were compared. The multiple scattering correction of the Lorenz-Mie theory based on the asymmetry factor affects the turbidity similarly as the use of mixing rule for refractive indices of multicomponent systems. A good correspondence between both theories was found only for small scattering inclusions fulfilling the approximate condition for diameter d < 0.3 λ. Only approximate agreement of the turbidity and refractive index fluctuations up to the diameters d < 5 λ can be observed for the present systems using both theories. The results obtained for the solid polymers were compared with model calculations for polystyrene latex under identical conditions: the latter are in a reasonable agreement with the expected trends (more pronounced dispersion and larger turbidity).