Sulfosuccinate and Sulfocarballylate Surfactants As Charge Control Additives in Nonpolar Solvents

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. (four double-chain sulfosuccinates and four triple-chain sulfocarballylates) were studied as charging agents for sterically-stabilized poly(methyl methacrylate) (PMMA) latexes in dodecane. Tail branching was found to have no significant effect on the electrophoretic mobility of the latexes, but the number of tails was found to influence the electrophoretic mobility. Triple-chain, sulfocarballylate surfactants were found to be more effective. Several possible origins of this observation were explored by comparing sodium dioctylsulfosuccinate (AOT1) and sodium trioctylsulfocarballylate (TC1) using identical approaches: the inverse micelle size, the propensity for ion dissociation, 1 the electrical conductivity, the electrokinetic or ζ potential, and contrast-variation small-angle neutron scattering. The most likely origin of the increased ability of TC1 to charge PMMA latexes is a larger number of inverse micelles. These experiments demonstrate a small molecular variation that can be made to influence the ability of surfactants to charge particles in nonpolar solvents, and modifying molecular structure is a promising approach to developing more effective charging agents.

The internal structure of poly(methyl methacrylate) latexes in nonpolar solvents

“…Fluorescence energy-transfer studies have shown that small molecules can distribute throughout the cores [103][104][105]. Other small molecules, such as residual hexane solvent [106] or surfactant charging agents [74,76], can also be distributed throughout the cores of the latexes. Given that molecules are able to partition throughout the volume of the latexes, the core polymers could be highly porous and therefore significantly less dense than the pure polymer.…”

“…Small-angle neutron scattering (SANS) has been used to study the composition and interaction of latexes by the Ottewill group at the University of Bristol [51,58,[67][68][69][70] and others [71,72] as well as to study the distribution of surfactants in charged latexes [73][74][75][76]. Small-angle X-ray scattering (SAXS) has also been used to study the interaction of such PMMA latexes [77,78].…”

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

“…These latexes are used because they have previously been shown to be amenable to analysis by small-angle scattering techniques. 10 Dispersions without AOT SAXS measurements were performed on the 76 nm latexes with no added surfactant and with 100 mM AOT added. As X-rays are sensitive to differences in electron density, the technique is sensitive only to the PMMA core of the latexes.…”

“…In water, λ B is ∼ 1 nm, which is why ions can be easily stabilized in the solvent. In hydrocarbon solvents, λ B is ∼ 30 nm, which means that dissociation fractions are low for moderately sized ions [6][7][8][9][10][11] or that very large diffuse ions must be used to attain high dissociation fractions. 12 Poly(methyl methacrylate) (PMMA) latexes with poly(12-hydroxystearic acid) (PHSA) graft copolymer stabilizer layers, developed in collaboration between the University of Bristol and ICI in the 1980s, 13 have long been established as a model system for studying interactions in nonpolar solvents.…”

“…Since it was reported in 2005 that these latexes could be charged by sodium dioctylsulfosuccinate (Aerosol OT or AOT) surfactant, 14 these particles have been increasingly used as a model for studying the nature of charged colloids in nonpolar solvents. 8,10,11,[15][16][17][18][19][20][21][22][23][24][25] From all the studies in the literature on these particles, the impact of systematically varying many of parameters of the system (such as particle size, surfactant concentration, surfactant polarity, and surfactant counterion) and the impact on the charge of the particle has been studied. 26 However, one of the variables that can impact the electrophoresis of charged particles has surprisingly not been reported for PMMA latexes charged by AOT: the particle volume fraction.…”