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Interaction between colloidal particles on an oil-water interface in dilute and dense phases

Parolini, Lucia; Law, Adam D.; Maestro, Armando; Buzza, D. Martin A.; Cicuta, Pietro


Lucia Parolini

Adam D. Law

Armando Maestro

Pietro Cicuta


The interaction between micron-sized charged colloidal particles at polar/non-polar liquid
interfaces remains surprisingly poorly understood for a relatively simple physical chemistry
system. By measuring the pair correlation function g(r) for different densities of polystyrene
particles at the decane–water interface, and using a powerful predictor–corrector inversion
scheme, effective pair-interaction potentials can be obtained up to fairly high densities, and
these reproduce the experimental g(r) in forward simulations, so are self consistent. While at
low densities these potentials agree with published dipole–dipole repulsion, measured by
various methods, an apparent density dependence and long range attraction are obtained when
the density is higher. This condition is thus explored in an alternative fashion, measuring the
local mobility of colloids when confined by their neighbors. This method of extracting
interaction potentials gives results that are consistent with dipolar repulsion throughout the
concentration range, with the same magnitude as in the dilute limit. We are unable to rule out
the density dependence based on the experimental accuracy of our data, but we show that
incomplete equilibration of the experimental system, which would be possible despite long
waiting times due to the very strong repulsions, is a possible cause of artefacts in the inverted
potentials. We conclude that to within the precision of these measurements, the dilute pair
potential remains valid at high density in this system.

Journal Article Type Conference Paper
Publication Date May 20, 2015
Journal Journal of Physics: Condensed Matter
Print ISSN 0953-8984
Electronic ISSN 1361-648X
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 27
Issue 19
Pages 194119
APA6 Citation Parolini, L., Law, A. D., Maestro, A., Buzza, D. M. A., & Cicuta, P. (2015). Interaction between colloidal particles on an oil-water interface in dilute and dense phases. Journal of physics. an Institute of Physics journal. Condensed matter, 27(19), 194119. doi:10.1088/0953-8984/27/19/194119
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Additional Information Journal title: Journal of Physics: Condensed Matter; Article type: paper; Article title: Interaction between colloidal particles on an oil–water interface in dilute and dense phases; Copyright information: © 2015 IOP Publishing Ltd; Date received: 2014-09-20; Date accepted: 2014-11-18; Online publication date: 2015-04-29