Aggregation Behavior of Nonionic Surfactants Synperonic A7 and A50 in Aqueous Solution

Li, Mei; Rharbi, Yahya; Winnik, Mitchell A.; Hahn, Kenneth G.

doi:10.1006/jcis.2001.7625

Cited by 7 publications

(7 citation statements)

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“…Analysis of these fluorescence decays in terms of the Poisson quenching model yielded an aggregation number N agg of 300 for A7 and 40 for A50. That study found that N agg values for freshly prepared samples of A7 increase modestly with increasing surfactant concentration 13b. While the A50 micelles were stable, the A7 micelles grow over a period of a month to N agg = 700.…”

Section: Resultsmentioning

confidence: 89%

“…While the A50 micelles were stable, the A7 micelles grow over a period of a month to N agg = 700. Quasielastic light scattering experiments gave a hydrodynamic radius of 3.4 nm for A50 and 5.5 nm for A7, and diffusion coefficients of 2.2 × 10 -7 cm 2 /s for A50 and 1.4 × 10 -7 cm 2 /s for A7 13c. The large aggregation number for micelles of A7 make it unlikely that these micelles are spherical in shape .…”

Section: Resultsmentioning

confidence: 99%

“…Characterization of Aqueous A50 and A7 Solutions. Recently Li et al investigated aqueous solutions of Synperonic A7 and A50 by means of dynamic (DLS) and static light scattering (SLS) as well as by fluorescence probe techniques using 1-ethylpyrene as the probe. UV−vis and steady-state fluorescence experiments showed that aqueous A7 and A50 solutions can solubilize pyrene and ethylpyrene.…”

Section: Resultsmentioning

confidence: 99%

“…The dependence of k obs for 1 on the concentration of empty A7 micelles is shown as the bottom line in Figure . The concentration of micelles is calculated with eq 4 with N agg = 300 and cmc = 0.22 mM . Values of k obs were calculated by fitting individual I E decays to an exponential profile.…”

Section: Resultsmentioning

confidence: 99%

“…The nonionic surfactants Synperonic A7 and A50 ((CH 3 -(CH 2 ) x -CH 2 -(OCH 2 -CH 2 ) y -OH) were supplied by ICI Americas Inc., Wilmington, Delaware and were used as received. In our laboratory, Li et al carried out 1 H NMR measurements at 400 MHz on solutions of these surfactant in CDCl 3 . They found x = 8, y = 6.5 for A7 and x = 9.2, y = 53.7 for A50.…”

Section: Methodsmentioning

confidence: 99%

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Solute Exchange in Synperonic Surfactant Micelles

et al. 2002

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We describe experiments that examine the rates of solute exchange in micelles formed from the surfactants Synperonic A7 and Synperonic A50. These surfactants are linear alkane (mixed C13 and C15) ethoxylates with mean degrees of ethoxylation of 6.5 for A7 and 53.7 for A50. The solute is gycerol-1,2-distearate-3-pyrenebutyrate, 1. Solutions containing on average 0.4 molecules of 1 per micelle show both excimer and monomer fluorescence. Excimer emission originates from micelles containing at least two pyrene chromophores. In A50, 1 forms aggregates that do not exchange on a time scale of weeks. When solutions of A7 are treated with an excess of empty micelles, the excimer fluorescence decays with a pseudo-firstorder rate that depends on the concentration of empty micelles. Because 1 is so insoluble in water, its exchange involves either fusion of two micelles to form a short-lived supermicelle, or fragmentation of a micelle into submicelles, which then grow back to form normal micelles. The corresponding rate constants are k 2 ) 8.7 × 10 4 M -1 s -1 for the second-order process and k1 ) 0.85 s -1 for the first-order process. These rates are more than an order of magnitude slower than the rates of micelle fusion and fragmentation for Triton-X100 micelles (Rharbi et al. J. Am. Chem. Soc. 2000, 122, 6242) determined by the same technique. We discuss possible sources for these differences.

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Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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