A new method to determine micellar aggregation numbers: positron annihilation lifetime spectroscopy

Micellar Radii and High Aggregation Numbers in a 0.6 M NaCl Sodium Dodecylsulfate Solution Determined through Positron Annihilation Lifetime Spectroscopy

“…2 However, the o-Ps org lifetime of those micelles containing one or more molecules of quencher was found to be not as short, as compared to τ 4 0 , as one would have expected from its high reaction rate constant with Ps measured in pure dodecane; this was attributed to some localization of the quencher molecules near the water/micelle interface. 2 The aim of the present paper is to extend and further establish the usefulness of our method based on PALS to determine both R mic and N ag by selecting cases where other, more conventional techniques have shown limitations. To this end, we have undergone the study of aqueous SDS solutions in the presence of large amounts (0.6 M) of NaCl, as a function of temperature (T).…”

“…For the sake of space, the final equation is not given but can be deduced from the treatments developed in our previous work. 1,2 The Ps radius, R Ps in eq 6, was calculated on the basis of one of the simplest bubble models: 15 in the T range explored, R Ps varies very smoothly, from 0.312 to 0.315 nm between 305 and 343 K, respectively; it was verified that moderate changes in these values would not affect significantly the results to come. The viscosity of the (SDS + NaCl) solutions, η in eq 6, was calculated from the viscosity of pure water, η w , at each T, and the NaCl concentration, C NaCl , according to 16…”

“…2 Once added to the system, a solute (quencher) known to react effectively with Ps and soluble only in the organic core of the micelles will distribute over the micelles according to Poisson's law. 6,7 In those micelles which happen to contain no quencher molecules, the o-Ps lifetime remains the same as in the absence of quencher, τ 4 0 .…”

Positron annihilation lifetime spectroscopy (PALS): a probe for molecular organisation in self-assembled biomimetic systems

“…In this 'bubble' state the oPs occupies a much larger volume than the 'free' oPs, B0.4 nm as compared to 0.053 nm. [12][13][14][15] 2.2 6.0 0.12 Fig. [12][13][14][15] As oPs aqu can be distinguished from oPs micelle , and diffusion occurs from the aqueous phase to the hydrocarbon core, then reaction kinetics or solubilisation dynamics of additives may be examined.…”

“…[12][13][14] A potentially exciting and fruitful application of PALS is in the unique insight it can lend to the effect of drugs on these matrices and further, the interaction of the delivery vehicle with biological membranes, to aid in developing therapeutic interventions. [12][13][14] A potentially exciting and fruitful application of PALS is in the unique insight it can lend to the effect of drugs on these matrices and further, the interaction of the delivery vehicle with biological membranes, to aid in developing therapeutic interventions.…”