ISSN:
1435-1536
Keywords:
CMC
;
counterionbinding
;
CTAB
;
SDS
;
bile salt
;
Na-cholate
;
urea
;
mixedmicelles
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Micellization characteristics and counterion binding properties of cetyltrimethyl ammonium bromide (CTAB) in presence of urea and a nonionic surfactant polyoxyethylene sorbitan monolaurate (PSML), and of sodium dodecyl sulphate (SDS) in presence of urea as well as of several mixtures of CTAB with a bile salt, sodium cholate (NaC), and sodium chloride have been studied. Both urea and PSML have increased the critical micelle concentration (CMC) of the surfactants, the former being more effective than the latter. The analysis of the results supports the pseudophase micellar model to hold over the mass action model. Pure CTAB micelles bind more counterions (96 %) than pure SDS micelles (87 %), and the decreasing effect of urea on the binding is less in case of the former than the latter. A 4∶1 mixture of CTAB and sodium cholate (NaC) can micellize and the micelles bind 87 % bromide ion, whereas 2∶1 and 1∶1 mixtures do not micellize. Micelles of 1∶1 mixture of CTAB and NaCl can bind counter bromide ions to the extent of 92 %. The limiting concentrations of urea required to effect counterion binding by CTAB and SDS micelles are 0.15 mol dm−3 and 0.25 mol dm−3, respectively. Such effect is shown by PSML on CTAB at a ratio 0.28∶1. The activation energy of conduction of SDS has increased in the presence of urea up to a concentration of 4 mol dm−3, at higher concentrations the activation energy has decreased, the effect being more for surfactant concentration above CMC than below.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01410582
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