Diffusivity data and reaction kinetics as probes for self-assembling: Cationic surfactant–chloroform system

Herein two sensitive techniques, i.e., NMR self-diffusion measurements and dielcometry are involved to test the association of cationic surfactant 4-aza-1-tetradecyl-1-azoniabicyclo[2.2.2]octane bromide (BC-14) and polyethyleneimine hydrophobized with tetradecyl moieties (PEI-14) in their chloroform solutions. The data obtained make it possible to nominate these methods as highly powerful instruments for the identification of a very uncooperative aggregation. Mixed BC-14/PEI-14 association is probably observed only at a relatively high polymer concentration, which is indicated by a decrease in the diffusivity of surfactant molecules. Aggregation is strongly promoted by the addition of water, with a high [water]/[BC-14] molar ratio of 60 attained. Even a very slight association has a serious impact on the reactivity, the pre-concentration effect and the shift of acid–base equilibrium of solutes. A 4-fold acceleration of the reactivity of an organophosphorus pollutant occurs in the BC-14 reverse micelles due to the concentration of reagents and changes in their microenvironment, which strongly supports the very idea of association. The high binding constants derived from the analysis of kinetic data provide evidence on high degree of concentration of compounds, while changes in the microenvironment affect their ionization. These impacts may be of key importance in analytical procedures and the chemical reactivity of compounds in nonpolar media.