Quantitative correlation of counterion (x) affinity to ionic micelles and x- and temperature-induced micellar growth (spherical - wormlike micelles - vesicles) for x = 5-methyl- and 5-methoxysalicylate ions

Yusof , NS; Khan , MN. (2012) Quantitative correlation of counterion (x) affinity to ionic micelles and x- and temperature-induced micellar growth (spherical - wormlike micelles - vesicles) for x = 5-methyl- and 5-methoxysalicylate ions. Journal of Physical Chemistry B, 116 (7). ISSN 1520-6106

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Abstract

The semiempirical kinetic method has been used to determine the ratio of cetyltrimethylammonium bromide, CTABr, micellar binding constants of counterions X (K(X)) and Br (K(Br)), i.e., K(X)/K(Br) (= R(X)(Br)) for X = dianionic 5-methyl- and 5-methoxysalicylate ions. The values of K(X) and K(Br) have been derived from the kinetic parameters obtained in the presence of spherical/nonspherical and spherical micelles, respectively. The values of R(X)(Br) remain essentially independent of [CTABr] within its range 0.005-0.015 M for both dianionic 5-methyl- and 5-methoxysalicylate ions. The increase in temperature from 35 to 55 °C decreases the values of R(X)(Br) from 796 to 53 for 5-methylsalicylate ions and from 89 to 7.0 for 5-methoxysalicylate ions. Rheological properties of 0.015 M CTABr solutions containing ≥0.01 M counterionic salt, M(2)X, show indirectly the presence of unilamellar vesicles, ULV, and long linear, entangled, and branched wormlike micelles, WM, at, respectively, 35 and 55 °C for X = dianionic 5-methylsalicylate ion. However, such studies show WM and probable spherical micelles, SM, at, respectively, 35 and 55 °C for X = dianionic 5-methoxysalicylate ions. It has been shown that, at a constant [CTABr], the micellar structural transitions from SM-to-WM-to-vesicles may be correlated quantitatively with the values of R(X)(Br) regardless of whether such micellar structural transitions occur due to variation in the values of [M(2)X] at a constant temperature or due to variation in temperature at a constant [M(2)X].

Item Type: Article
Creators:
  1. Yusof , NS
  2. Khan , MN.
Journal or Publication Title: Journal of Physical Chemistry B
Additional Information: Department of Chemistry, Faculty of Science, University of Malaya , 50603 Kuala Lumpur, Malaysia
Uncontrolled Keywords: Chemistry
Subjects: Q Science > QD Chemistry
R Medicine
Divisions: Faculty of Science > Dept of Chemistry
Depositing User: Mr. Faizal Hamzah
Date Deposited: 22 Mar 2012 10:19
Last Modified: 22 Mar 2012 10:19
URI: http://eprints.um.edu.my/id/eprint/2963

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