Surfactant property of linear alkanes with two pyrrolidone moieties in both termini

Linear alkanes with two pyrrolidone groups in both termini [abbreviation: 1,n‐dipyrrolidonyl alkane (1,n‐DPA) (n=3, 5, 9, and 12)] were synthesized. Their surface activities were evaluated in terms of surface tension, and compared with those of a few kinds of surfactants. Among 1,n‐DPAs, 1,3‐, 1,5‐, and 1,9‐DPAs were fully soluble in water and surface‐active: especially 1,9‐DPA showed a surface tension value of γW/A 32.8 mN/m at 5.9×10 −2 mol/L or 1.7 wt% and was suggested as a nonionic surfactant with simple structure and moderate activity. Critical miceller concentration (CMC) of 1,9‐DPA was 1.45×10 −2 mol/L. Surface tension values of 1,5‐ and 1,9‐DPAs were lower than those of the corresponding monofunctional pyrrolidones, N‐propyl and N‐pentylpyrrolidones. Minimum area per surfactant molecule (A min ) decreased with increase of methylene chain length in the series of 1,n‐DPAs. The results suggested that 1,n‐DPA favorably chooses a loop structure at air/water interface.