ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We present a detailed comparison between the low frequency behavior of the electric birefringence (as measured by the Kerr constant, B) and of the real part of the dielectric increment Δcursive-epsilon′, in aqueous colloidal dispersions of nearly monodisperse, elongated, polytetrafluoroethylene (PTFE) particles with adjustable surface charge. The electric charge and, consequently, the ζ-potential of the particles, is modified by adding a nonionic surfactant to the dispersion, as discussed in the first paper of this series [J. Chem. Phys. 103, 8228 (1995)]. We find that both B and Δcursive-epsilon′ decrease upon decreasing the absolute value of the ζ-potential. Upon increasing the ionic strength, B and Δcursive-epsilon′ display opposite behavior: B decreases while Δcursive-epsilon′ increases. We propose an expression which connects B to the standard electrokinetic model and compare the experimental data to a calculation based on spheroids with thin double layers. If we calculate B and Δcursive-epsilon′ using the particle ζ-potential obtained from electrophoretic mobility measurements, the theory qualitatively reproduces the experimental results, but systematically underestimates the values of both B and Δcursive-epsilon′. If, instead, we take the ζ-potential as an adjustable parameter, we can reconcile both B and Δcursive-epsilon′, although the values of ζ are larger than those derived from electrophoretic mobility measurements. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.477257
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