| Autor: |
Khokhar V; Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India., Anjali; Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India., Pandey S; Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India. |
| Jazyk: |
angličtina |
| Zdroj: |
Langmuir : the ACS journal of surfaces and colloids [Langmuir] 2023 Apr 11; Vol. 39 (14), pp. 5129-5136. Date of Electronic Publication: 2023 Mar 31. |
| DOI: |
10.1021/acs.langmuir.3c00189 |
| Abstrakt: |
Due to the ease of tailoring the physicochemical properties by simply changing a constituent or composition, deep eutectic solvents (DESs) possess widely varying capabilities for surfactant self-assembly that could depend on the surfactant headgroup charge. The self-aggregation process of three surfactants, sodium dodecylsulfate (SDS), cetyltrimethylammonium bromide (CTAB), and Triton X-100 (TX-100), dissolved in DESs composed of a lanthanide salt (Ln) and urea (U) is investigated. The role of the identity of the metal salt is assessed by using [La(NO 3 ) 3 ·6H 2 O] (La) and [Ce(NO 3 ) 3 ·6H 2 O] (Ce) and that of the composition is deciphered by systematically changing the mole ratio of the metal salt and urea in (La/U) DESs. The response to a fluorescence probe pyrene-1-carboxaldehyde along with electrical conductance and surface tension measurements is used to obtain the critical aggregation concentration (CAC). While the CACs in 1:3.5 (Ln/U) for SDS are significantly lower than that in water, the values are marginally higher for CTAB and TX-100. The CACs for all three surfactants are similar in 1:3.5 (La/U) and (Ce/U) DESs, implying that the identity of the metal in the salt is not so important. Increasing the urea composition in (La/U) DESs results in increased CAC for SDS and CTAB; however, a minimal decrease in CAC is observed for TX-100. From the temperature dependence of CAC, thermodynamic parameters, Δ G agg 0 , Δ H agg 0 , and Δ S agg 0 , of the surfactant self-aggregation process are estimated. These parameters reveal that while at a lower urea content, the SDS/CTAB self-assembly process is enthalpically driven, it becomes entropically favored at higher urea concentrations. The TX-100 self-aggregation in these DESs is found to be strongly enthalpically favored and entropically un-favored. These parameters are explained as a combination of passage of the solvophobic surfactant chain from the bulk DES to the aggregate pseudo-phase and differential orientation/organization of DES constituents around surfactant monomers and/or aggregates. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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