Investigation of the micellization of cationic tetradecyltrimethylammonium bromide in aqueous solution of crystal violet dye: Understanding of the impacts of alcohols and temperature

Abstract

Exploring dye-surfactant interactions is crucial for understanding the properties of their mixtures in various applications. It is of utmost importance to explore the effects of experimental factors on the dye-surfactant interactions. This study examines the micellization of the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) in the presence of crystal violet (CV) dye in different alcohol solutions including methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), and 1-butanol (1-BuOH). Through conductometric analysis, the effects of varying alcohol compositions and temperature on the critical micelle concentration (CMC), degree of ionization ($\alpha$), counterion binding ($\beta$), and thermodynamic parameters ($∆G_m^0$, $∆H_m^0$, and $∆S_m^0$) were investigated. The findings show that alcohol causes an increase in CMC, with longer-chain alcohols (1-PrOH and 1-BuOH) having a stronger effect on TTAB + CV aggregation. The CMC values of the investigated system in 5 % alcohol solutions were found to follow this order: CMC (aq. 1-BuOH) > CMC (aq. MeOH) > CMC (aq. EtOH) > CMC (aq. 1-PrOH). As temperature rises at a constant alcohol concentration, CMC initially decreases but then increases due to dehydration of the surfactant’s hydrophilic and hydrophobic regions. Thermodynamic analysis reveals that micellization is mainly entropy-driven at lower temperatures, with dominant hydrophobic interactions. As temperature increases, both enthalpy and entropy play significant roles, on the micellization to be occurred through hydrophobic and ion-induced dipole interactions. The molar heat capacity (${∆C}_m^0$) assessment indicates the identical orientation of the alcohol chain within the TTAB micellar core. The study also highlights the enthalpy-entropy compensation effect, revealing a strong correlation. By exploring these relationships between alcohol chain length and temperature with thermodynamic and physicochemical properties of surfactant systems, this research offers valuable insights for developing surfactant-based applications in academic and industrial fields.