Tuning of Micellar Structure and Dynamics in Aqueous Salt-Free Solutions of Cetyltrimethylammonium Mono- and Dichlorobenzoates
1996; American Chemical Society; Volume: 12; Issue: 3 Linguagem: Inglês
10.1021/la950965+
ISSN1520-5827
AutoresM. T. Carver, Tiffany Smith, Jeffrey C. Gee, A. Delichere, Eugenio Caponetti, L. J. Magid,
Tópico(s)Photochemistry and Electron Transfer Studies
ResumoMicelle formation and growth in salt-free aqueous solutions have been investigated for five cetyltrimethylammonium (CTA) mono- and dichlorobenzoates using small-angle neutron scattering (SANS) and rheological measurements. Manipulation of the chlorine substitution pattern provides an excellent means of tuning micellar morphology and solution properties. Two of the surfactants, CTA 2,6-dichlorobenzoate and CTA 2-chlorobenzoate, form Newtonian aqueous solutions containing roughly spherical micelles below ca. 70 mM. There follows a region with increasing concentration of significant micellar growth to prolate ellipsoids (or rigid, short cylindrical micelles), micellar overlap, and apparent maximum aggregation numbers, 〈n〉's, at ca. 200 and 167 mM (φ = 0.095 and 0.073), respectively. Above these latter concentrations, the SANS Qmax values scale as C1/2, characteristic of an entangled polymer-like micellar network. The three surfactants having chlorine substituents para and/or meta to the counterion's COO- gro...
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