The physicochemical properties and contact angle of sodium dodecyl sulfate in water–acetone with and without sodium nitrate (NaNO3)

Abstract

Conductivity measurements at room temperature were performed to study the physicochemical behavior of anionic surfactant SDS in water and acetone–water mixture in the presence and absence of NaNO3.The concentration of SDS was 0.05 M and the concentration of NaNO3 was 0.01 M and 0.05 M. We calculated the degree of dissociation (α) and critical micelle concentration (CMC) from the pre-micellar (S1) and post-micellar slopes (S2). When acetone is added to SDS, CMC and α increase, but decreased with an increase in NaNO3.The standard free energy of micellization (ΔGm°) was evaluated using CMC and α. Micellization becomes less likely when the acetone content is higher as the negative values of ΔGm° decrease, indicating less spontaneous micellization. Due to the electrostatic repulsion of the head groups, adding salt NaNO3 decreases the CMC of SDS. A drop shape analyzer (DSA-25E) was used to measure the contact angles (CAs). For SDS, acetone and NaNO3 molecules mixed at varying concentrations, simulations were conducted.