Stabilizing strands: Exploring the kinetic stability of polymer-coated emulsions with surface specific spectroscopy

Emulsions on the scale of 100 s of nm in diameter traditionally achieve long-term colloidal stability (> 1 month) through surfactants or a combination of surfactant and polymer. The stability of emulsions coated with only polyelectrolyte remains largely unknown. Here, we introduce an emulsion system coated with the surface-active polymer, poly(acrylic acid) (PAA) that stabilizes hexadecane-in-water emulsions with a marked dependence on pH and ionic strength. Surface specific vibrational sum frequency scattering spectroscopy (VSFSS) provides a molecular picture of PAA organization at the hexadecane-water droplet interface while dynamic light scattering and zeta potential measures the colloidal stability as a function of pH and salt concentration. We find that a steric layer of polymer alone stabilizes emulsions despite having a low zeta potential (