Charging Poly(methyl Methacrylate) Latexes in Nonpolar Solvents: Effect of Particle Concentration

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-d surfactant in latex core contrast-matched solvent were used to study the former, and electrokinetic modeling was used to study the latter. As the same amount of AOT-d 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.

A Neutron Scattering Study of the Structure of Poly(dimethylsiloxane)-Stabilized Poly(methyl methacrylate) (PDMS–PMMA) Latexes in Dodecane

“…In this work, we report the first use of SANS measurements to study a system of PDMS-stabilized PMMA colloids. This extends the body of work using small-angle scattering to study PMMA latexes ,− that was previously limited to the PHSA-stabilizer. We do this by synthesizing PMMA latexes using covalently linked PDMS stabilizers to produce smaller colloids than previously reported , with a goal of accessing a size regime suitable for small-angle scattering measurements.…”

“…Early interparticle scattering work confirmed that PHSA-stabilized PMMA nanoparticles in alkanes represented a good model hard-sphere system, even with bimodal size mixtures , and at high density. , More recently, it has been shown that through the addition of charge additives typically studied for electrophoretic display applications, similar PMMA nanoparticles display different structure at high densities because of their increased repulsion . Recently, their internal structure was also studied using small-angle neutron scattering (SANS), revealing the localization of absorbed surfactant charge-additives. − …”

Precise Self-Positioning of Colloidal Particles on Liquid Emulsion Droplets

“…Millipore Ultrapure 18.2 MΩ·cm water was used throughout. The hydrophobic PMMA (polymethymethacrylate, stabilized by polyhydroxystearic acid; fluorescently labeled by DiIC 18 ) − and the hydrophobic Sicastar silica (trimethylsilyl-coated) CPs used were spherical and fluorescently labeled and had diameters of ∼2.4 μm (PMMA) and 1.5 and 5–7 μm (silica). Nanoparticles (trimethylsilyl-coated silica, Sicastar), which are 250 nm in radius, have been employed as well.…”

Adjusting the charging behavior of TiO2 with basic surfactants in an apolar medium for electrophoretic displays

“…where e 1 and e 2 are particle charges, ε r is the relative dielectric constant of the medium, ε 0 is the dielectric constant of vacuum, k B is the Boltzmann constant, and T is the temperature. For instance, λ B of water is 0.7 nm at 25 °C, while that of apolar medium is around 30 nm (such as dodecane's is 28 nm) [15][16][17] . On the one hand, this means that the capacitance of the electric double layer on particles in apolar media is small, which will result in the difficulty for particles to obtain the surface charge 18 .…”