Surface Chemical Properties and Micellization of Disodium Hexadecyl Diphenyl Ether Disulfonate in Aqueous Solution

The surface tension of disodium hexadecyl diphenyl ether disulfonate (C 16 ‐MADS) was measured at different NaCl concentrations (0.00–0.50 mol L −1 ) and temperatures (298.0–318.0 K) using the drop‐volume method. The results show that, with increasing temperature, the critical micelle concentration (CMC) of C 16 ‐MADS increases slightly, but the maximum surface adsorption capacity ( Γ max ) at the air–water interface decreases. When the concentration of NaCl was increased from 0.00 to 0.50 mol L −1 , the CMC of C 16 ‐MADS decreased from 1.45 × 10 −4 to 4.10 × 10 −5 mol L −1 , but the surface tension at the CMC ( γ cmc ) was not affected. When the concentration of NaCl was increased at 298.0 and 303.0 K, the Γ max of C 16 ‐MADS increased. When the temperature was increased from 308.0 to 318.0 K, the surface excess concentration ( Γ max ) of C 16 ‐MADS abnormally decreased from 2.26 to 1.41 μmol m −2 with increasing NaCl concentration. The micellization free energy ( Δ G m ∘ ) decreased from −63.98 to −76.20 kJ mol −1 with increase of temperature and NaCl concentration. The micellar aggregation number ( N m ) of disodium hexadecyl diphenyl ether disulfonate (C 16 ‐MADS) was determined using the molecule fluorescence probe method with pyrene as probe and benzophenone as quencher. The results show that an appropriate N m could be measured only at surfactant concentration above the CMC. The N m increased with an increase in C 16 ‐MADS concentration, but the micropolarity in the micelle nucleus decreased. The temperature had little effect on N m . Compared with typical single hydrophilic headgroup surfactants, aggregates of C 16 ‐MADS exhibit different properties.