Incorporating Intermicellar Interactions in the Fitting of SANS Data from Cationic Wormlike Micelles

Abstract

Small-angle neutron scattering (SANS) from cationic wormlike micellar solutions composed of hexadecyltrimethylammonium bromide (CTABr) and hexadecylpyridinium bromide (CPyBr) in deuterated water was studied at 40 degrees C as a function of surfactant and salt concentrations. Two scattering functions of semiflexible chains incorporating excluded volume effects, with and without the intermicellar interactions, were used in SANS data model fitting. Two needed changes were made in the well-accepted models. Extensive and systematic SANS data analysis suggests the robustness of these corrected scattering functions when the intermicellar interactions are included. The influence of the headgroups and ionic strength on the contour length and micellar flexibility of these two systems was demonstrated on the basis of the quantitative structural information obtained from the model fitting. Micellar flexibility was found to depend on surfactant concentration, even when intermicellar interactions were taken into account, despite predictions to the contrary.

Wormlike micelles in poly(oxyethylene) surfactant solution: Growth control through hydrophilic-group size variation

“…New experiments may be devised based on such techniques. For example, since the nonionic systems of our study are free from electrostatic interactions, they can be profitably investigated utilizing recent developments in neutron scattering [45] and atomistic simulation [46]. Such research may provide deeper understanding of the elusive flexibility of wormlike micelles as well as bring out improvements for the computational aspects of colloid and interface science.…”

“…Thus, these systems are very interesting from scientific and industrial standpoints. Therefore a large amount of research employing different materials and various techniques (such as rheology, cryo-TEM, light scattering, small-angle X-ray, and neutron scattering) has been carried out to characterize these systems [2,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. However, most of the past and recent work is focused on ionic surfactant systems [20][21][22][23][24][25].…”

On the dissolution state of cellulose in cold alkali solutions

“…As a comparison, we show as a dashed curve the pure form factor scattering, i.e., assuming SðqÞ ¼ 1 for semi flexible chains with excluded volume interactions. This parametrized form factor was derived by Pedersen and Schurtenberger (1996) from computer simulations (Chen et al 2006). In the present calculation we have used the experimentally determined M w ¼ 29 kg/mol corresponding to an average contour length of L h i % 82 nm, assuming a length of 0.515 nm (Schulz et al 2000) for every glucose unit, a cross sectional radius of 0.25 nm and a Kuhn length l K ¼ 2:3 nm (corresponding to approximately 4 glucose units).…”

Morphology of Comb-Shaped Proton Exchange Membrane Copolymers Based on a Neutron Scattering Study

“…Therefore, the wormlike elongated aggregates model proposed for wormlike micelles is chosen to be the form factor, F WL (q). 22 Because the TEM image shows that these objects are compactly arranged, a hard disk structure factor, S HD (q), is employed to account for such interference. 23 The use of the hard disk structure factor is based on the assumption that the radial interparticle interaction among the long aggregates is expected to be much more significant than the axial interaction in the current q range.…”