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NMR study of the influence of n‐alkanol co‐surfactants on reverse micelles in quaternary microemulsions of cetyltrimethylammonium bromide (CTAB)
Author(s) -
Mills Amanda J.,
Britton Melanie M.
Publication year - 2017
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4392
Subject(s) - microemulsion , chemistry , micelle , pulmonary surfactant , bromide , alcohol , hexane , analytical chemistry (journal) , chromatography , organic chemistry , aqueous solution , biochemistry
The effects of different n ‐alkanol co‐surfactants on the size, shape, composition and dynamics of reverse micelles (RMs) in cetyltrimethylammonium bromide (CTAB)/ n ‐alkanol/ n ‐hexane/water and CTAB/ n ‐alkanol/ n ‐pentane/water microemulsions were investigated using T 2 relaxation and pulsed gradient stimulated echo nuclear magnetic resonance (NMR) measurements and molecular modelling. NMR T 2 relaxation times and diffusion coefficients were determined for the surfactant and co‐surfactant in these CTAB quaternary reverse microemulsions, for a range of medium chain length alcohol co‐surfactants, from 1‐butanol to 1‐heptanol. These data revealed a slight RM size dependency on co‐surfactant chain length, with RM sizes tending to decrease with increasing alcohol chain length. Molecular modelling of CTAB/ n ‐alkanol/ n ‐hexane/water RMs suggested a variation in RM shape with co‐surfactant chain length, where those formed with pentanol were found to be least spherical and those formed with heptanol the most spherical. The NMR data also revealed differences in the behaviour of the micellar structures in the CTAB/ n ‐pentanol/ n ‐hexane/water reverse microemulsion, compared with the other reverse microemulsions in this study, where CTAB was found to be distributed between two environments, which then combined to form larger micelles. The origins of these differences remain unclear. Copyright © 2016 John Wiley & Sons, Ltd.