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Brownian dynamics in strongly scattering porous media ‐ dynamic light scattering with single‐mode matching
Author(s) -
Rička Jaroslav
Publication year - 1994
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19940790106
Subject(s) - scattering , light scattering , dynamic light scattering , brownian motion , optics , matrix (chemical analysis) , opacity , porous medium , diffusion , physics , statistical physics , materials science , porosity , nanotechnology , quantum mechanics , nanoparticle , composite material
Brownian motions in porous media represent a challenging problem not only from a theoretical but also from an experimental point of view. A very powerful technique for the measurement of Brownian motions is Dynamic Light Scattering (DLS). For our problem, however, the classic version of DLS is useless because the porous matrix scatters very strongly and the particles to be measured are completely masked. Sometimes it is possible to suppress the background scattering by matching the refractive indices of the matrix and the confined liquid, but this restricts the applicability to a handful of suitable model systems. We have introduced a new technique which overcomes this difficulty: The keyword is single‐mode matching and the idea is to select from the complicated random light field generated by the strongly scattering medium only a single mode so that the contribution from the matrix to the selected mode vanishes because of destructive interference. The first experimental results on the dynamics of latex particles in aqueous suspensions confined in a packing of glass beads are very promising. Their quantitative analysis demonstrates clearly the feasibility of measuring the diffusion coefficient within an opaque strongly scattering porous medium.