Dynamic and molecular association in premicellar aqueous solutions of dicarboxylate amino acid‐based surfactant as studied by ¹H NMR

Abstract

We examined a series of amino acid-based surfactants with two carboxylic groups separated by a spacer of one, two, or three carbon atoms with sodium and calcium counterions in the premicellar concentration region near the CMC. 1 H nuclear magnetic resonance (NMR) spectroscopy and NMR diffusometry techniques were used to study the local environment, association, and translational dynamics of the surfactant's molecules. We measured the self-diffusion coefficients of the micelles, calculated the effective hydrodynamic radii, and determined the temperature region in which the premicelles exist. With an increase in temperature from 295 to 335 K, the premicellar state of the surfactant is replaced by the monomeric state.

An Investigation of the Effect of pH on Micelle Formation by a Glutamic Acid-Based Biosurfactant

“…Divalent cations, however, can balance the surfactant's negative charge and reduce this repulsion. Arkhipov, et al used 1 H NMR to show that the addition of divalent calcium ions to solutions containing Glutamic acid-based surfactants leads to the formation of premicellar aggregates [25]. These structures dissociated when the solution temperatu re was increased above 315 K [25].…”