Duolayers at the Air/Water Interface: Improved Lifetime through Ionic Interactions

Abstract

Ionic interactions to stabilize Langmuir films at the air/water interface have been used to develop improved duolayer films. Two-component mixtures of octadecanoic (stearic) acid and poly(diallyldimethylammonium chloride) (polyDADMAC) with different ratios were prepared and applied to the water surface. Surface pressure isotherm cycles demonstrated a significant improvement in film stability with the inclusion of the polymer. Viscoelastic properties were measured using canal viscometry and oscillating barriers, with both methods showing that the optimum ratio for improved properties was four octadecanoic acid molecules to one DADMAC unit (1:0.25). At this ratio it is expected multiple strong..