We show that depletion forces induced by surfactant micelles can be profitably exploited to perform an efficient a posteriori size fractionation of suspensions of optically anisotropic colloids. Efficiency and limits of the fractionation protocol are discussed both on 'model' and technical polydisperse lattices. This method can be used to single out fractions composed by long fibrillar particles, showing evidence of mesogenic behaviour. Depolarized dynamic light scattering is used to extract the particle translational and rotational diffusion coefficients D-T and D-R as a function of particle volume fraction. Both the concentration behaviour of D-T and the full shape of the depolarized correlation functions show distinctive and partially unexpected features.
Depletion-induced fractionation of optically anisotropic particles
PIERNO, MATTEO AMBROGIO PAOLO;
2002
Abstract
We show that depletion forces induced by surfactant micelles can be profitably exploited to perform an efficient a posteriori size fractionation of suspensions of optically anisotropic colloids. Efficiency and limits of the fractionation protocol are discussed both on 'model' and technical polydisperse lattices. This method can be used to single out fractions composed by long fibrillar particles, showing evidence of mesogenic behaviour. Depolarized dynamic light scattering is used to extract the particle translational and rotational diffusion coefficients D-T and D-R as a function of particle volume fraction. Both the concentration behaviour of D-T and the full shape of the depolarized correlation functions show distinctive and partially unexpected features.
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