Sagisaka, Masanobu ORCID: 0000-0001-9685-7524 , Endo, Takumi, Fujita, Kazuki, Umetsu, Yasushi, Osaki, Suzuna, Narumi, Tsuyoshi, Yoshizawa, Atsushi ORCID: 0000-0003-4272-3410 , Mohamed, Azmi, Guittard, Frédéric, Hill, Christopher ORCID: 0000-0002-9257-5244 and Eastoe, Julian (2021) Very low surface tensions with “Hedgehog” surfactants. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 631:127690. ISSN 0927-7757 (Print), 1873-4359 (Online) (doi:https://doi.org/10.1016/j.colsurfa.2021.127690)

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Abstract

Previous studies [Langmuir, 2014, 30, 21, 6057–6063, Phys. Chem. Chem. Phys., 2017,19, 23869-23877] have shown that surfactants bearing highly-methylated alkyl tails (so-called “hedgehog” groups) are able to reduce the limiting surface tension at the aqueous critical micelle concentration (CMC) to γCMC ~24 mN m-1, which is considerably lower than for common n-alkyl tail surfactants (30-40 mN m-1). In the quest to develop even more effective and efficient non-fluorinated surfactants, this study introduces new amphiphiles having double and triple hedgehog tails and examines relationships between surfactant structure and aqueous solution properties. Of particular interest are links between γCMC, the effective hydrophobic-tail layer density (ρ
layer) and total number of carbon and silicon atoms in the hydrophobic tails (N
C+Si). Interestingly, γCMC is seen to depend on ρ
layer rather than N
C+Si, and ρ
layer ~0.63gcm-3 appears to be an optimal surface layer density for promoting low γCMC. For a surfactant bearing trimethysilyl (TMS) chain tips, exchanging the surfactant counterions from Na+ to Mg2+ reduced γ
CMC from 23.8 mN m-1 to 21.5 mN m-1, which is very low for a hydrocarbon surfactant, and comparable to typical fluorinated surfactants. A new measure of the ability of different surfactants to lower surface tension is proposed, which is helpful for targeting low surface energy (tension) non-fluorinated surfactants. In terms of both γ
CMC and CMC TMS-terminal tips are shown to be key groups for promoting hydrophobicity and/or low surface tensions.

Item Type:	Article
Additional Information:	** Article version: AM ** Embargo end date: 31-12-9999 ** From Elsevier via Jisc Publications Router ** History: accepted 04-10-2021; issued 08-10-2021. ** Licence for AM version of this article: This article is under embargo with an end date yet to be finalised.
Uncontrolled Keywords:	highly-methyl-branched-tail (hedgehog) surfactants; hydrophobicity
Subjects:	Q Science > Q Science (General) T Technology > T Technology (General)
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Science (SCI)
SWORD Depositor:	Publications Router
Last Modified:	24 May 2024 14:04
URI:	http://gala.gre.ac.uk/id/eprint/34046

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