Synergy, competition, and the “hanging” polymer layer: Interactions between a neutral amphiphilic ‘tardigrade’ comb co-polymer with an anionic surfactant at the air-water interface

Anna Slastanova, Richard A. Campbell, Tim Snow, Elizabeth Mould, Peixun Li, Rebecca J.L. Welbourn, Meng Chen*, Eric Robles, Wuge H. Briscoe

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

2 Citations (Scopus)


Understanding the structure of polymer/surfactant mixtures at the air-water interface is of fundamental importance and also of relevance to a variety of practical applications. Here, the complexation between a neutral ’tardigrade’ comb co-polymer (consisting of a hydrophilic polyethylene glycol backbone with hydrophobic polyvinyl acetate grafts, PEG-g-PVAc) with an anionic surfactant (sodium dodecyl sulfate, SDS) at the air-water interface has been studied. Contrast-matched neutron reflectivity (NR) complemented by surface tension measurements allowed elucidation of the interfacial composition and structure of these mixed systems, as well as providing physical insights into the polymer/surfactant interactions at the air-water interface. For both polymer concentrations studied, below and above its critical aggregation concentration, cac, (0.2 cac and 2 cac, corresponding to 0.0002 wt% or 0.013 mM and 0.002 wt% or 0.13 mM respectively), we observed a synergistic cooperative behaviour at low surfactant concentrations with a 1–2 nm mixed interfacial layer; a competitive adsorption behaviour at higher surfactant concentrations was observed where the polymer was depleted from the air-water interface, with an overall interfacial layer thickness ~1.6 nm independent of the polymer concentration. The weakly associated polymer layer “hanging” proximally to the interface, however, played a role in enhancing foam stability, thus was relevant to the detergency efficacy in such polymer/surfactant mixtures in industrial formulations.

Original languageEnglish
Pages (from-to)181-194
Number of pages14
JournalJournal of Colloid and Interface Science
Early online date30 Nov 2019
Publication statusPublished - 1 Mar 2020



  • Air-water interface
  • Comb co-polymer
  • Competition
  • Foaming
  • Neutron reflectivity
  • Polymer/surfactant interactions
  • Synergy

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