Synthesis, surface and interface tension of N-lauroyl-L-Valine sodium

Abstract

N-lauroyl-L-Valine sodium (NLLVS) was synthesized and characterized by FT-IR, 1H-NMR spectrometry. Surface and interface tension were measured by wilhelmy plate and spinning drop method. The effects of surfactant concentration, salt, polymer and mixed surfactant on interfacial tension were studied in detail. The critical micelle concentration (cmc) was 6 × 10−3 mol/L and cmc oil was 8 × 10−3 mol/L. The equilibrium interfacial tension (IFTequ) first decreased and then increased with NLLVS increasing. Mixed salts were less effective at reducing interfacial tension than NaCl and CaCl2, while the higher concentration of NaCl was needed to obtain the same IFT as added CaCl2 and NaCl/CaCl2. The lowest IFTequ obtained at the NaCl concentration of 10% when the ratio of NLLVS and Alkyl polyoxypropylene polyoxyethylene ether sulfate (P12) was 2:8. Polyacrylamide was disadvantage to reduce IFT, while polyacrylamide was arranged more tightly by NLLVS.