Static and dynamic electric birefringence in model colloidal dispersions of intrinsically anisotropic particles

Piazza, Roberto and Degiorgio, Vittorio and Giardini, Mario Ettore and Mantegazza, Francesco (1992) Static and dynamic electric birefringence in model colloidal dispersions of intrinsically anisotropic particles. In: Structure and Dynamics of Strongly Interacting Colloids and Supramolecular Aggregates in Solution. NATO ASI Series . Springer, pp. 557-570. ISBN 9789401051224

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Abstract

Electric birefringence measurements in model solutions of fluorinated polymer colloids provide a sensitive way to understand the mechanisms of electric polarization in colloidal systems, thanks to the high intrinsic optical anisotropy of these materials. We present here static and dynamic measurements in suspensions of charged PTFE (polytetrafluoroethylene) rods and PFA (alkoxyvinylether -tetrafluoroethylene copolymer ) spheres. In particular we show that the contribution of counterion clouds is strongly related to interparticle interaction effects and is almost negligible in the dilute limit, that the volume fraction dependence of the second virial coefficient of the Kerr constant seems to scale with the inverse of the ionic strength and that the experimental evidence of an apparent permanent dipole moment may be explained in terms of a fluctuational model of surface charge distribution on the colloidal particle.