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 (ΔG°mic), standard free energy of adsorption (ΔG°ad), 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, ΔG°ad and ΔG°mic 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. Copyright © 2004 by AOCS Press.