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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

DOI: 10.1016/j.jcis.2019.11.017 DOI Help

Authors: Anna Slastanova (University of Bristol) , Richard A. Campbell (Institut Laue-Langevin) , Tim Snow (University of Bristol; Diamond Light Source) , Elizabeth Mould (University of Bristol) , Peixun Li (ISIS Facility) , Rebecca J. L. Welbourn (ISIS Facility) , Meng Chen (Procter & Gamble Beijing Innovation Centre) , Eric Robles (Procter & Gamble Newcastle Innovation Centre) , Wuge H. Briscoe (University of Bristol)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Journal Of Colloid And Interface Science

State: Published (Approved)
Published: November 2019

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.

Journal Keywords: Polymer/surfactant interactions; air-water interface; synergy; competition; foaming; comb co-polymer; neutron reflectivity

Subject Areas: Chemistry

Technical Areas: