Investigation of Micellar Media Containing â-CDs
J. Phys. Chem. B, Vol. 101, No. 38, 1997 7389
(2) (a) Sanemasa, I.; Akamine, Y. Bull. Chem. Soc. Jpn. 1987, 60,
2059. (b) Fujiki, M.; Deguchi, T; Sanemasa, I. Bull. Chem. Soc. Jpn. 1988,
61, 1163. (c) Sanemasa, I.; Takuma, T.; Deguchi, T. Bull. Chem. Soc. Jpn.
1989, 62, 3102.
(3) Tee, O. S. AdV. Phys. Org. Chem. 1994, 29, 1.
(4) Jezequel, D.; Mayaffre, A. Letellier, P. Can. J. Chem. 1991, 69,
1865.
light on the influence of cyclodextrin on the behavior of the
surfactant. Cyclodextrin has no effect on the properties of
surfactant micelles once these have formed (in particular, it does
not alter â, km, or Ks, the partition constant governing the
distribution of MNTS between the aqueous and micellar
pseudophases), but it increases the total surfactant concentration
(5) (a) Okubo, T.; Kitano, H.; Ise, N. J. Phys. Chem. 1976, 80, 2661.
(b) Satake, I.; Ikenoue, T.; Takeshita, T.; Hayakawa, K.; Maeda, T. Bull.
Chem. Soc. Jpn. 1985, 58, 2746. (c) Satake, I.; Yoshida, S.; Hayakawa, K.;
Maeda, T.; Kusumoto, Y. Bull. Chem. Soc. Jpn. 1986, 59, 3991. (d) Palepu,
R.; Reinsborough, V. C. Can. J. Chem. 1988, 66, 325. (e) Palepu, R.;
Reinsborough, V. C. Can. J. Chem. 1989, 67, 1550.
(6) (a) Park, J. W.; Song, H. J. J. Phys. Chem. 1989, 93, 6454. (b)
Park, J. W.; Choi, N. H.; Kim, J. H. J. Phys. Chem. 1996, 100, 769.
(7) (a) Diaz, A.; Quintela, P. A.; Schuette, J. M.; Kaifer, A. E. J. Phys.
Chem. 1988, 92, 3537. (b) Dharmawardana, U. R.; Christian, S. D.; Tucker,
E. E.; Taylor, R. W.; Scamehorn, J. F. Langmuir 1993, 9, 2258.
(8) (a) Junquera, E.; Aicart, E.; Tardajos, G. J. Phys. Chem. 1992, 96,
4533. (b) Junquera, E.; Tardajos, G.; Aicart, E. J. Phys. Chem. 1993, 97,
1243. (c) Junquera, E.; Tardajos, G.; Aicart, E. Langmuir 1993, 9, 1213.
(9) Hersey, A.; Robinson, B. H.; Kelly, H. C. J. Chem. Soc., Faraday
Trans. 1 1986, 82, 1271.
(10) Mwakibete, H.; Cristantino, R.; Bloor, D. M.; Wyn-Jones, W.;
Holzwarth, J. F. Langmuir 1995, 11, 57 and references therein.
(11) (a) Bunton, C. A.; Savelli, G. AdV. Phys. Org. Chem. 1986, 22,
213. (b) Cordes, E. H. Pure Appl. Chem. 1978, 50, 617.
(12) (a) Romsted, L. S. Surfactants in Solution; Lindman, B., Mittal,
K. L., Eds.; Plenum Press: New York, 1984; Vol. 2. (b) Romsted, L. S. J.
Phys. Chem. 1985, 89, 5107, 5113.
(13) (a) Bunton, C. A.; Romsted, L. S.; Sepulveda, L. J. Phys. Chem.
1980, 84, 2611. (b) Al-Lohedan, H.; Bunton, C. A.; Romsted, L. S. J. Phys.
Chem. 1981, 85, 2123 and references therein.
at which micelles begin to form (cmcapp) and reduces [surfmon max
]
(cmcreal), the concentration of surfactant that remains in
monomer form at total surfactant concentrations greater than
cmcapp. The increase in cmcapp with [CD] is due to complex-
ation of surfactant by cyclodextrin, which reduces the concen-
tration of surfactant that is free to form micelles. The reduction
in cmcreal is unexplained but agrees with previous reports of
the effects of CD18 and other organic molecules19 on micelli-
zation.
At total surfactant concentrations higher than cmcapp, com-
petition between the micellization and complexation processes
results in the presence of an appreciable concentration of
uncomplexed cyclodextrin, which is the same for all total
surfactant concentrations above cmcapp. Traditionally, surfac-
tant-CD complexation constant values have been obtained from
changes in cmcapp caused by the presence of CD. These
methods would be useless due to the existence in the solution
of a significant amount of noncomplexed CD. The difference
between cmcapp and total CD concentration does not show the
monomer concentration present in the medium (cmcreal). In fact,
evidence was reported in the literature about cmcapp values lower
than the total CD concentration.21 The results in Tables 1 and
(14) Castro, A.; Leis, J. R.; Pen˜a, M. E. J. Chem. Soc., Perkin Trans. 2
1989, 1861.
(15) (a) Castro, A.; Leis, J. R.; Pen˜a, M. E. J. Chem. Soc., Perkin Trans.
2 1990, 1221. (b) Bravo, C.; Herve´s, P.; Leis, J. R.; Pen˜a, M. E. J. Phys.
Chem. 1990, 94, 8816. (c) Bravo, C.; Leis, J. R.; Pen˜a, M. E. J. Phys.
Chem. 1992, 96, 1957. (d) Garc´ıa-R´ıo, L.; Iglesias, E.; Leis, J. R.; Pen˜a,
M. E. J. Phys. Chem. 1992, 96, 7821.
2 show that free monomer concentration in equilibrium (cmcreal
)
depends on CD, in agreement with recent results18 that report
evidence that the presence of CD induces surfactant aggregation
under the cmc.
(16) Hashimoto, S.; Thomas, J. K. J. Am. Chem. Soc. 1985, 107, 4655.
(17) (a) Wan Yunus, W. M. Z.; Taylor, J.; Bloor, D. M.; Hall, D. G.;
Wyn-Jones, E. J. Phys. Chem. 1992, 96, 8979. (b) Sasaki, K. J.; Cristian,
S. D.; Tucker, E. E. J. Colloid Interface Sci. 1990, 134, 412. (c) Funasaki,
N.; Yodo, H.; Hada, S.; Neya, S. Bull. Chem. Soc. Jpn. 1992, 65, 1323
(and references therein).
(18) Jiang, Y. B.; Wang, X. J. Appl. Spectrosc. 1994, 48, 1428.
(19) (a) Hunter, R. J. Foundations of Colloid Science; Clarendon
Press: Oxford, 1987; Vol. 1. (b) Schwuger, M. Ber. Bunsen.-Ges. Phys.
Chem. 1971, 75, 167.
Acknowledgment. Financial support from Xunta de Galicia
(project XUGA 20906B93) and from the Direccio´n General de
Investigacio´n Cient´ıfica y Te´cnica of Spain (project PB93-0524)
is gratefully acknowledged.
References and Notes
(1) (a) Bender, M.; Komiyama, M. Cyclodextrin Chemistry; Springer-
Verlag: New York, 1978. (b) Saenger, W. Angew. Chem., Int. Ed. Engl.
1980, 19, 344. (c) Fendler, J. H.; Fendler, E. J. Catalysis in Micellar and
Macromolecular Systems; Academic Press: New York, 1975.
(20) Hoffmann, H.; Ulbricht, W. Z. Phys. Chem. (Munich) 1977, 106,
107.
(21) Aman, E. S.; Serve, D. J. Colloid Interface Sci. 1990, 138, 365.