Closo-dodecaborate-based dianionic surfactants with distorted classical morphology : synthesis and atypical micellization in water

Hleli, Belhssen (author), Medoš, Žiga (author), Ogrin, Peter (author), Tošner, Zdeněk (author), Kereïche, Sami (author), Gradzielski, Michael (author), Urbič, Tomaž (author), Bešter-Rogač, Marija (author), Matějíček, Pavel (author)

Hypothesis: To challenge the classical concept of step-like micellization of ionic surfactants with singular critical micelle concentration, novel amphiphilic compounds with bulky dianionic head and the alkoxy tail connected via short linker, which can complex sodium cations, were synthesized in the form of disodium salts. Experiment: The surfactants were synthesized by opening of a dioxanate ring attached to closo-dodecaborate by activated alcohol, which allows for attachment of alkyloxy tails of desired length to boron cluster dianion. The synthesis of the compounds with high cationic purity (sodium salt) is described. Self-assembly of the surfactant compound at air/water interface and in bulk water was studied by tensiometry, light and small angle X-ray scattering, electron microscopy, NMR spectroscopy, MD simulations and by isothermal titration calorimetry, ITC. The peculiarities in the micelle structure and formation were revealed by thermodynamic modelling and MD simulations of the micellization process. Findings: In an atypical process, the surfactants self-assemble in water to form relatively small micelles, where the aggregation number is decreasing with the surfactant concentration. The extensive counterion binding is a key characteristic of the micelles. The analysis strongly indicates complex compensation between the degree of bound sodium ions and the aggregation number. For the first time, a three-step thermodynamic model was used to estimate the thermodynamic parameters associated with micellization process. Diverse micelles differing in size and counterion binding can (co–)exist in the solution over the broad concentration and temperature range. Thus, the concept of step-like micellization was found inappropriate for these types of micelles.

• Language: English
• Keywords: dodecaborate, surfactants, self-assembly, micelles, calorimetry, simulations
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2023
• Number of pages: Str. 809-819
• Numbering: Vol. 648
• PID: 20.500.12556/RUL-147049
• UDC: 544.27
• ISSN on article: 0021-9797
• DOI: 10.1016/j.jcis.2023.06.013
• COBISS.SI-ID: 156408323
• Publication date in RUL: 22.06.2023

Record is a part of a journal

• Title: Journal of colloid and interface science
• Shortened title: J. colloid interface sci.
• Publisher: Elsevier
• ISSN: 0021-9797
• COBISS.SI-ID: 5255941

Licences

• License: CC BY-NC 4.0, Creative Commons Attribution-NonCommercial 4.0 International
• Link: http://creativecommons.org/licenses/by-nc/4.0/
• Description: A creative commons license that bans commercial use, but the users don’t have to license their derivative works on the same terms.

Secondary language

• Language: Slovenian
• Keywords: dodekaborat, surfaktanti, samourejanje, micele, kalorimetrija, simulacije