Spreading of aqueous surfactant solutions on oil substrates: Superspreaders vs non-superspreaders

Nina M Kovalchuk; Masanobu Sagisaka; Hinata Komiyama; Mark J H Simmons

doi:10.1016/j.jcis.2024.02.031

Spreading of aqueous surfactant solutions on oil substrates: Superspreaders vs non-superspreaders

J Colloid Interface Sci. 2024 May:661:1046-1059. doi: 10.1016/j.jcis.2024.02.031. Epub 2024 Feb 6.

Authors

Nina M Kovalchuk¹, Masanobu Sagisaka², Hinata Komiyama², Mark J H Simmons³

Affiliations

¹ School of Chemical Engineering, University of Birmingham, B15 2TT, UK. Electronic address: n.kovalchuk@bham.ac.uk.
² Graduate School of Science and Technology, Hirosaki University, 036-8561, Japan.
³ School of Chemical Engineering, University of Birmingham, B15 2TT, UK.

PMID: 38335789
DOI: 10.1016/j.jcis.2024.02.031

Abstract

Hypothesis: The question of why aqueous solutions of some surfactants demonstrate a rapid spreading (superspreading) over hydrophobic solid substrates, while solutions of other similar surfactants do not, has no definitive explanation despite numerous previous studies. The suggested hypothesis for this study assumes that once the spreading coefficient of surfactant is positive, there is a concentration range for solutions of any surfactant which demonstrates rapid spreading. As it is impossible to calculate spreading coefficients for solid substrates, we compare the spreading performance of known superspreaders and non-superspreaders on liquid (oil) substrate.

Experiments: The kinetics of spreading of aqueous solutions of a series of branched ionic surfactants and non-ionic trisiloxane surfactants on two liquid substrates was studied and compared with the spreading of a surfactant-free liquid, silicone oil. Both dynamic and equilibrium spreading coefficients were calculated using measured surface and interfacial tensions.

Findings: There is no difference in spreading rate on liquid substrate between solutions of surfactants proven as superspreaders (while spreading on solid substrate) or non-superspreaders. A rapid spreading (superspreading) with the characteristic rate of spreading O(10²-10³) mm²/s occurs if the dynamic spreading coefficients exceeds the positive threshold value. If the dynamic spreading coefficient is negative or slightly positive, complete wetting still occurs, but the spreading is slow with the spreading rate is O(1) mm²/s. Spreading exponents for surfactant solutions in the rapid spreading regime are considerably larger than for the surfactant-free liquid. A number of spreading and dewetting patterns were observed depending on the surfactant type, its concentration and substrate.

Keywords: Branched ionic surfactants; Interfacial tension; Mineral oil; Rapeseed oil; Spreading coefficient; Spreading exponent; Spreading patterns; Superspreading; Trisiloxane non-ionic surfactants.