Synthesis and study of the surface properties of long‐chain alkylnaphthalene sulfonates

Abstract Long‐chain alkylnaphthalene sulfonates were synthesized by means of a Wurtz‐Fittig reaction, and the basic properties were studied in water at 30°C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γCMC). The following values were calculated: area per molecule at the CMC (ACMC), standard free energy change of micellization (ΔGmico), standard free energy of adsorption (ΔGado), and the “efficiency” of a surfactant in reducing surface tension (pC20). The micelle aggregation numbers were measured through steady‐state fluorescence‐quenching methods. As the chain length of the hydrocarbon of n‐alkylnaphthalene sulfonate increased, the Krafft temperature increased, the surface tension decreased, the value of CMC decreased, pC20 increased, ΔGado and ΔGmico became more negative, and the micelle aggregation number increased. The results showed that sodium α‐(n‐decyl)naphthalene sulfonate (DNS) had a high pC20, low Krafft temperature, and lower CMC than other surfactants in this study. Thus, DNS and the other n‐alkylnaphthalene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency, oil recovery, and dyes.