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Charging poly(methyl methacrylate) latexes in nonpolar solvents: Effect of particle concentration

DOI: 10.1021/acs.langmuir.7b02257 DOI Help

Authors: Gregory N. Smith (University of Bristol) , Silvia Ahualli (University of Granada) , Angel V. Delgado (University of Granada) , David A. J. Gillespie (University of Bristol) , Roger Kemp (Merck Chemicals Ltd) , Jocelyn Peach (University of Bristol) , Jonathan C. Pegg (University of Bristol) , Sarah Rogers (ISIS-STFC) , Olga Shebanova (Diamond Light Source) , Nathan Smith (Merck Chemicals Ltd) , Julian Eastoe (University of Bristol)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Langmuir

State: Published (Approved)
Published: October 2017
Diamond Proposal Number(s): 9753

Abstract: The electrophoresis of a well-established model system of charged colloids in nonpolar solvents has been studied as a function of particle volume fraction at constant surfactant concentration. Dispersions of poly(12-hydroxystearic acid)-stabilized poly(methyl methacrylate) (PMMA) latexes in dodecane were prepared with added Aerosol OT surfactant as the charging agent. The electrophoretic mobility (µ) of the PMMA latexes is found to decrease with particle concentration. The particles are charged by a small molecule charging agent (AOT) at finite concentration, and this makes the origin of this decrease in µ unclear. There are two suggested explanations. The decrease could either be due to the reservoir of available surfactant being exhausted at high particle concentrations or the interactions between the charged particles at high particle number concentrations. Contrast-variation small-angle neutron scattering measurements of PMMA latexes and deuterated AOT-d34 surfactant in latex core contrast-matched solvent were used to study the former, and electrokinetic modeling were used to study the latter. As the same amount of AOT-d34 is found to be incorporated with the latexes at all volume fractions, the solvodynamic and electrical interactions between particles are determined to be the explanation for the decrease in mobility. These measurements show that, for small latexes, there are interactions between the charged particles at all accessible particle volume fractions and that it is necessary to account for this to accurately determine the electrokinetic ζ potential.

Subject Areas: Chemistry

Instruments: I22-Small angle scattering & Diffraction