Effect of synergists on organic pigment particle charging in apolar media

Abstract

The current work investigates the apolar charging behavior of organic pigment particles and the role that synergists play in regard to particle charging. Organic pigments are often used in apolar paints, inks, and most recently electrostatic lithography. For electrolithography to work, the particles must be both stable and possess the correct polarity and magnitude of charge. It is therefore important to better understand the charging behavior and potential charging mechanisms of these particles that have received little or no attention in the literature. Unfortunately, these already complex systems are further complicated by the fact that the stability of organic pigments is often improved through the use of synergists. Synergists are designed to enhance the adsorption of steric stabilizers to the particles. However, their effect on particle charging has not been previously published. In this study, the particle zeta potential is determined for apolar dispersions of magenta and cyan particles in heptane (with and without synergist present). The particles are dispersed with three different surfactants commonly used in apolar charging studies: Span 80, Aerosol-OT, and OLOA 11000. Acid-base interactions appear to play an important role, particularly for cyan. However, due to the complexity of these systems, any general rule must be applied with caution as the particle, surfactant, and synergist chemistry all determine the nature of the particle charge.

Charging Mechanism for Polymer Particles in Nonpolar Surfactant Solutions: Influence of Polymer Type and Surface Functionality

“…To infer the particles' equilibrium charging state in the absence of external electric fields, we extrapolate the fielddependent mobility to zero field strength (zero-f ield mobility), following a widely adopted strategy from past studies. 21,22,25,30,37,38 Prior to the measurements, the glass cuvette and dip cell were sonicated in tetrahydrofuran, wiped in a hot aqueous detergent solution, rinsed with methanol, and dried with air.…”

CelebratingSoft Matter's 10th Anniversary: Influencing the charge of poly(methyl methacrylate) latexes in nonpolar solvents

“…4 The charge of many types of colloids in low dielectric media has been reported. In addition to polymer nanoparticles, carbon black, 5,6 mineral oxides, 7,8 pigments, [9][10][11] and aerosols 12 have all been studied. In this article, the focus is a specific system of charged colloids: polymer brush stabilized poly(methyl methacrylate) (PMMA) latexes, where typically poly(12-hydroxystearic acid) (PHSA) is used as the steric stabilizer.…”

Effects of Reverse Micellar Structure on the Particle Charging Capabilities of the Span Surfactant Series

“…Many variables must be considered when studying charging events in nonpolar environments. The environment in which the system is being studied, the components of the system, and the formation of the surfactants into reverse micelles all affect the charging events in the system. , Previous studies in this field have focused mainly on how surfactant and particle chemistries interplay to obtain a maximum particle mobility. − Other studies have determined the effects of water content on the conductivities and maximum colloidal particle charges of apolar systems. , Impedance spectroscopy has also been used to investigate the role reverse micelles have in charge transport in apolar systems. − The solvent dielectric constant and structure have been shown to affect the critical micelle concentration and conductivity of Aerosol OT, even to the point that micelles, reverse or normal, will no longer form . Recent studies have investigated the effects of temperature and surfactant structure on the critical micelle concentration and maximum particle mobilities .…”

“…Current studies have used inverse micelles of Span 60 and Span 85 − as means of protein extraction from solution, while other studies have used inverse micelles of Span 80 to synthesize mesoporous titania membranes for ultrafiltration purposes . Many recent studies have looked at the ability of Span surfactants to charge particles in apolar solvents, measuring the magnitudes and signs of the particle electrophoretic mobilities. ,,,, However, most studies have looked only at how the chemistry of the surfactant headgroup affects the charging behavior. − ,, The authors’ most recent study has shown that the magnitude of particle charge, of 30 nm magnesia particles, increases as the tail length of the Span species increases. Preliminary small-angle neutron scattering (SANS) data have suggested that this increase in charging corresponded to smaller inverse micelles.…”

“…3,6,7,27,28 However, most studies have looked only at how the chemistry of the surfactant headgroup affects the charging behavior. [4][5][6][7]28,29 The authors' most recent study 14 has shown that the magnitude of particle charge, of 30 nm magnesia particles, increases as the tail length of the Span species increases. Preliminary small-angle neutron scattering (SANS) data 14 have suggested that this increase in charging corresponded to smaller inverse micelles.…”