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Updated: Mar 17, 2026

Temperature-Controlled Assembly and Characterization of a Droplet Interface Bilayer
Published on: April 19, 2021
Duolayers at the Air/Water Interface: Improved Lifetime through Ionic Interactions
Emma L Prime1, David H Solomon1, Ian J Dagley2
1Department of Chemical & Biomolecular Engineering, University of Melbourne , Parkville, VIC 3010, Australia.
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 ionic interactions are formed along each polymer chain. Brewster angle microscopy showed decreased domain size with increased ratios of polyDADMAC, indicating that the polymer is interspersed across the surface. This new method to stabilize and increase the viscoelastic properties of charged monolayer films, using a premixed composition, will have application in areas such as water evaporation mitigation, optical devices, and foaming.
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