Counteranion Effect on Micellization of Cationic Gemini Surfactants 14-2-14: Hofmeister and Other Counterions

Abstract

The effect of counterions was investigated and analyzed to probe the principal ionic effects influencing the micellization behavior of dimeric cationic surfactant ethanediylbis(dimethyltetradecylammonium), referred to as gemini 14-2-14. The 30 counterions were classified to four different families depending on their nature: (1) small and inorganic counterions which are typically taken from the Hofmeister series were studied to focus on the effect of ion type; (2) n-alkyl carboxylate counterions were studied to focus on the effect of the hydrophobicity of counterions; (3) aromatic carboxylate counterions were included to focus on the effect of the position of substitutions; and (4) other counterions were included in order to shed light on other parameters. By investigating the critical micelle concentration (CMC), ionization degree of micelle (alpha), free energy of micellization (DeltaG(M)), and aggregation numbers N of the gemini surfactant with these different types of anions, we demonstrated the effect of different ion properties independently. This approach allowed us to describe the effect of counterions on the micellization behavior of the gemini surfactant in terms of complex interplay between hydrophobicity of anions and other ion properties such as counterion hydration, interfacial packing of ions, and ionic morphology. Indeed, our results clearly demonstrate that a counterion effect on micellization properties cannot be described as a result of one single parameter of ions, as is too often assumed, but rather the balancing effects cooperatively affect the propensity of counterions to form ion pairs with surfactant headgroups and the entropy gain upon micellization. These results provide new insight in understanding the effect of ions on the delicate balance of forces controlling aggregate morphology and solution properties of charged amphiphilic molecules.

Cooperative and Reciprocal Chiral Structure Formation of an Alanine‐Based Peptide Confined at the Surface of Cationic Surfactant Membranes

“…[3e, 4,7] FTIR measurements: To monitor the inter-and intramolecular interactions and molecular organization, FTIR measurements were performed on 100 mm solutions. We focused on two domains of the frequencies in particular, one region for the amide I bands of the peptides and another region for the symmetric and antisymmetric stretching bands n s and n as of the CH 2 chains.…”

Tuning Thermoresponsive Properties of Cationic Elastin-like Polypeptides by Varying Counterions and Side-Chains

“…23,24 and can also alter the micellization properties of gemini surfactants. 25,26,27 To study the effects of different counterions on thermoresponsive behavior, we focused on the …”

Specific ion effects on the micellization of aqueous mixed cationic/anionic surfactant systems with various counterions

“…The self-assembly of ionic surfactants is easily influenced by the factors affecting these forces. The factors include the chemical structure of surfactant molecules [5][6][7][8], such as the nature of headgroups and the nature of counterions, and the solution conditions [9][10][11][12][13][14][15][16][17][18], such as concentration, temperature, the pH, the ionic strength, and the presence of additives. The nature of surfactant counterion or the nature of counterions from the salts added to the surfactant solution [3][4][5][9][10][11][12][13][14][19][20][21][22][23] significantly affects the cmc, micelle size, micelle shape, micellar catalysis, emulsion size, interfacial property, rheological property, phase behavior, etc.…”