First Simultaneous Estimates of the Water Pool Core Size and the Interfacial Thickness of a Cationic Water-in-Oil Microemulsion by Combined Use of Chemical Trapping and Time-Resolved Fluorescence Quenching

Abstract

The first simultaneous experimental estimates of the water pool core size (R w) and the interfacial thickness (d) of a cationic water-in-oil microemulsion, CTAB/isooctane/n-hexanol/water, was achieved by the combined use of chemical trapping and the time-resolved fluorescence quenching. Our estimated values of R w = 29.1 ± 1.5 Å compares reasonably well with the reported size of the water pool core (32 Å) of a structurally and compositionally similar CTAB/dodecane/n-hexanol/water cationic water-in-oil microemulsion (Atik, S. S.; Thomas, J. K. J. Am. Chem. Soc. 1981, 103, 4367), and our estimated interfacial thickness (6.3 Å ± 0.3) is consistent with the recently estimated thickness for the hydration layer (10 Å) of the cationic CTAB/n-hexane/n-pentanol/water water-in-oil microemulsions (Giustini, M. et al. J. Phys. Chem. 1996, 100, 3190). To our knowledge, this is the first simultaneous experimental estimate of the size of the water pool core and interfacial thickness of a cationic water-in-oil microemulsion using a chemical reaction.

Solvation dynamics of coumarin 480 in neutral (TX-100), anionic (SDS), and cationic (CTAB) water-in-oil microemulsions

“…Hence, the observed dynamics is not the dynamics of 1-hexanol in isooctane/1-hexanol (9:1, v/v) mixture; rather it implies the dynamics inside the microemulsion. The size of the water pool (r w ) of the isooctane/CTAB/1-hexanol/water at w 0 ¼ 22:8 is 29.1 A A as reported by Das et al [19]. Whereas at w 0 ¼ 40:6, the size of the water pool (r w ) of a structurally and compositionally similar reverse micelle (dodecane/CTAB/1-hexanol/water) is 54 A A [20].…”

“…The previous work on SDS, CTAB, and TX-100 microemulsions suggests that like ternary microemulsions these are also spherical in nature and swell with increasing water content of the microemulsions [16][17][18][19][20]. Thus, only difference between these microemulsions and ternary systems is the presence of 1-hexanol at the interface in addition to the presence of headgroup, counterion, and Ôbound waterÕ.…”

“…Structural feature of the microemulsion (w/o) formed by TX-100, cyclohexane, 1-hexanol, and water has been well studied [17,18]. Cetyltrimethylammonium bromide (CTAB) is also formed by quaternary water-in-oil microemulsion in the presence of isooctane, 1-hexanol, and water [19]. Das et al [19] first simultaneously estimated the water pool size and the interfacial thickness of CTAB/isooctane/1-hexanol/ water microemulsion by combined use of chemical trapping and fluorescence quenching method.…”

“…Cetyltrimethylammonium bromide (CTAB) is also formed by quaternary water-in-oil microemulsion in the presence of isooctane, 1-hexanol, and water [19]. Das et al [19] first simultaneously estimated the water pool size and the interfacial thickness of CTAB/isooctane/1-hexanol/ water microemulsion by combined use of chemical trapping and fluorescence quenching method. Atik and Thomas [20] determined the size of the water pool of structurally and compositionally similar w/o microemulsion (CTAB/dodecane/n-hexanol/water) by fluorescence quenching method.…”

Morphology and size control of nanocalcium carbonate crystallised in reverse micelle system with cationic surfactant cetyltrimethylammonium bromide

“…There have been some investigations on the preparation of reverse micelles using cetyltrimethylammonium bromide (CTAB) as surfactant [26][27][28][29]. With the existence of the cosurfactant, it is liable for CTAB to form reverse micelles, and the droplets' dimensions can be controlled by changing the volume of water, surfactant and cosurfactant.…”