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

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

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
Volume561
DOIs
StatePublished - Mar 1 2020
Externally publishedYes

Funding

We acknowledge funding from the Engineering and Physical Science Research Council (EPSRC Case Awards). We also thank Procter & Gamble for financial support. We thank the Institut Laue-Langevin for allocations of neutron beam time on FIGARO (DOI: https://doi.org/10.5291/ILL-DATA.9-12-380 ) and STFC ISIS Neutron and Muon Source on INTER (DOI: https://doi.org/10.5286/ISIS.E.RB2000016 ). Dr Luisa Islas is thanked for her help with the ISIS experiment, as Dr Andrew Mellor (Krüss) for helpful discussions on the bubble pressure measurement. Prof Craig Butts, Paul Lawrence and Sarah Michel are thanked for assistance with NMR analysis. Dr Frank Hülskötter at Procter & Gamble Service GmbH is thanked for many helpful discussions. Mr Gerard Langley is thanked for the tardigrade illustration. We acknowledge funding from the Engineering and Physical Science Research Council (EPSRC Case Awards). We also thank Procter & Gamble for financial support. We thank the Institut Laue-Langevin for allocations of neutron beam time on FIGARO (DOI: https://doi.org/10.5291/ILL-DATA.9-12-380) and STFC ISIS Neutron and Muon Source on INTER (DOI: https://doi.org/10.5286/ISIS.E.RB2000016). Dr Luisa Islas is thanked for her help with the ISIS experiment, as Dr Andrew Mellor (Krüss) for helpful discussions on the bubble pressure measurement. Prof Craig Butts, Paul Lawrence and Sarah Michel are thanked for assistance with NMR analysis. Dr Frank Hülskötter at Procter & Gamble Service GmbH is thanked for many helpful discussions. Mr Gerard Langley is thanked for the tardigrade illustration.

Keywords

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

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