Abstract
We present a comprehensive study of the aggregation properties of zwitterionic micelles of oxime-functionalized surfactants and their mixed micellar systems with conventional cationic CTABr and nonionic Tween® 80 surfactants. Analysis of the micellar effects on the reaction rates toward activated esters is also completed. Specifically, aggregation properties of micelles of amphiphilic 1-alkyl-3-methyl-2-(oximinomethyl)imidazolium and 1-alkyl-3(1-oximinoethyl)pyridinum bromides (alkyl=CnH2n+1, where n=12, 16) and their mixed micellar systems with CTABr and Tween® 80 have been investigated. The changes in micellar properties and reaction rates toward 4-nitrophenyl esters of diethyl phosphoric (NPDEP), diethyl phosphonic (NPDEPN), and toluenesulphonic (NPOTos) acids, with increase of pH ensuring deprotonation of specific oximate moiety, have been studied. We focused on the changes of micellar properties of mixed micelles depending on the mixture composition and the deprotonation degree of the functional oximate group. The critical micelle concentration (cmc) values, degrees of counterion binding (β), and size of micellar aggregates were obtained using surface tension measurements, dynamic light scattering method, bromide selective electrode, and by solubilization of hydrophobic dye Orange OT. The surface excess concentration (Гmax, μmol/m2), minimum area per molecule (Amin), interaction parameters (βm), standard Gibbs free energy of adsorption (ΔGadso) and micellization (ΔGmo), and excess free energy of micellization (ΔGex) have been evaluated. Micellar effects of the systems studied on the acyl transfer reaction rates were shown to increase with higher fraction of deprotonated oxime and can be treated in the framework of a pseudophase partitioning model. These results provide new information on (i) control the reactivity of the organized molecular systems and (ii) elaboration the basis for designing pH-responsive supramolecular assemblies.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Colloids and Surfaces A: Physicochemical and Engineering Aspects
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
