Influence of surfactants on a pre-adsorbed cationic layer: Removal and modification

Finian J Allen; Chris L Truscott; Rebecca J L Welbourn; Stuart M Clarke

doi:10.1016/j.jcis.2020.12.047

Influence of surfactants on a pre-adsorbed cationic layer: Removal and modification

J Colloid Interface Sci. 2021 Apr 15:588:427-435. doi: 10.1016/j.jcis.2020.12.047. Epub 2020 Dec 19.

Authors

Finian J Allen¹, Chris L Truscott², Rebecca J L Welbourn³, Stuart M Clarke⁴

Affiliations

¹ Department of Chemistry and BP Institute, University of Cambridge, Cambridge, UK. Electronic address: fa316@cam.ac.uk.
² Department of Chemistry and BP Institute, University of Cambridge, Cambridge, UK. Electronic address: clt45@cam.ac.uk.
³ ISIS Pulsed Neutron Facility, Harwell Science and Innovation Campus, STFC, Rutherford Appleton Laboratory, Didcot, Oxon, UK. Electronic address: becky.welbourn@stfc.ac.uk.
⁴ Department of Chemistry and BP Institute, University of Cambridge, Cambridge, UK. Electronic address: stuart@bpi.cam.ac.uk.

PMID: 33429339
DOI: 10.1016/j.jcis.2020.12.047

Abstract

Removal of organic species from solid surfaces is a crucial process. The use of oppositely charged surfactants provides a potential method for enhanced removal. Neutron reflectometry has been used to investigate the complex behaviour of a pre-adsorbed and tenacious layer of the cationic surfactant didodecyldimethylammonium bromide (DDAB) on a mica surface, during exposure to different organic species in solution. The anionic surfactant sodium dodecylsulfate (SDS) was shown to be able to remove the cationic layer, but only if anionic micelles were present in solution. To facilitate comparison with the behaviour of a non-ionic surfactant, the direct adsorption of pentaethylene glycol monododecyl ether (C₁₂E₅) to mica was also studied; low surface coverage adsorption was seen at the critical micelle concentration and above. C₁₂E₅ was then found not to remove the cationic layer, but did include into the layer to some degree. The presence of cationic surfactant on the mica was however shown to significantly modify the adsorption behaviour of the non-ionic surfactant.

Keywords: Adsorption; C(12)E(5); DDAB; Mica; Neutron reflectometry; SDS; Surfactant.