Open AccesspH Changes in the Micelle–Water Interface of Surface-Active Ionic Liquids Dictate the Stability of Encapsulated Curcumin: An Insight Through a Unique Interfacial Reaction between Arenediazonium Ions and t-Butyl Hydroquinone
Author(s) -
Saima Afzal,
Mohd Sajid Lone,
Nighat Nazir,
Aijaz Ahmad Dar
Publication year - 2021
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.1c01119
Subject(s) - chemistry , pulmonary surfactant , counterion , micelle , alkyl , critical micelle concentration , ionic bonding , colloid , ion , inorganic chemistry , sodium dodecyl sulfate , kinetics , vesicle , chemical engineering , organic chemistry , aqueous solution , membrane , biochemistry , physics , quantum mechanics , engineering
The chemical kinetic (CK) method, which involves the reduction of 4-hexadecylbenzenediazonium ions (16-ArN 2 + ) by antioxidants (in the present case, TBHQ) occurring exclusively at the interface of the association colloids, was employed to establish the changes in the chemical reactivity of anionic surface-active ionic liquids (SAILs) as a function of the concentration and the composition in their mixed states. We used sodium dodecyl sulfate and different SAILs based on the dodecylsulfate surfactant containing 1-alkyl-3-methylimidazolium cations as counterions having a varying alkyl chain length of 4 (bmim), 8 (omim), and 12 (ddmim) carbon atoms. The structural transitions of aggregates of the SAILs from the micellar to vesicular form were observed as a function of concentration in single surfactant systems and as a function of composition in mixed surfactant systems. Results of the reduction kinetics of 16-ArN 2 + at the interface of such aggregates, which depends on the acid/base equilibria at the interface, gave an insight into the changes in the interfacial H + ions with the change in the hydrophobicity of the counterions of SAILs and the morphological changes from micelles to vesicles as a function of concentration or composition. These changes in the interfacial pH correlate very well with the stability of curcumin within these self-assemblies, which exclusively depends on the pH of the medium and highlights the importance of the results obtained from the CK method in selecting the appropriate medium/conditions for the stabilization of the bioactive molecules.