The Role of Intermolecular Interactions in the Micellization Process of Alkyltrimethyl Ammonium Bromides in Water

Abstract

The micellization process of model cationic surfactants, alkyltrimethylammonium bromides with different alkyl chain length: dodecyl-(C12TAB), tetradecyl-(C14TAB) and hexadecyl- (C16TAB) has been investigated by the conductivity measurements over the temperature range 298.2 K–313.2 K. Understanding micelle formation requires its complete thermodynamic parameters, which were estimated by applying the proposed alternative derivation of pseudo-phase model. The critical micelle concentration (CMC), standard free Gibbs energy (ΔmicG0), enthalpy (ΔmicH0) and entropy (ΔmicS0) of micellization were analysed as a function of the increase in alkyl chain and temperature. At lower temperatures, the micellization in each case was found to be entropy-driven due to the increase in bulk water entropy. London or dispersion interactions are responsible for the cohesion between the apolar chains in the micelles and increase as the length of chains increases. ΔmicH0 reflects the contribution of London interactions, electrostatic repulsion between head groups and removing the alkyl chains from water (dehydration of CH2 and CH3 groups). As the temperature is increased, less energy is required for dehydration and hence the enthalpy of micellization became more exothermic and its effect more significant. The enthalpy-entropy compensation phenomenon was observed for all studied surfactants.

Synthesis and Micellization of Carbosilane Sulfonate Surfactants with Short Alkyl Chains

“…The β value is reduced as the alkyl group is elongated in the following order: methyl < ethyl < propyl < butyl < pentyl < hexyl. Furthermore, this result was also confirmed by dynamic light scattering experiments. , …”

Photo-Responsive Control of Adsorption and Structure Formation at the Air–Water Interface with Arylazopyrazoles

“…1 This dominant influence of the alkyl chain length on the bulk CMC and on interfacial properties is consistent with that of classical surfactants with different alkyl tails where the length of the hydrophobic tail increases the surfactants' surface activity. 42,43 At this point, we have to note that also the photo-stationary state (PSS) of the photoswitches can have an influence on their performance in the bulk and at the interface. The PSS of both H-AAP and octyl-AAP is, however, >91% for switching in both directions, as discussed in the Supporting Information (Figure S2).…”

Amphiphilic azobenzenes: Antibacterial activities and biophysical investigation of their interaction with bacterial membrane lipids

“…As it was commonly observed with surface-active molecules [19] including alkyl derivatives of quaternary ammonium compounds [20,21], an increase in the length of the nonpolar alkyl chain reduces the value of the CMC. The γ CMC observed for the 4b-4d compounds are similar and much lower than that observed for 4a.…”