Surface properties of aqueous systems of new nonionic double-chain surfactants and their mixtures with dilauroylphosphatidylcholine

Three new double-chain nonionic surfactants with the same chain length as dilauroylphosphatidylcholine (DLPC) have been synthesized with polar groups based on lysine. They are monodisperse (NNepsilon)-N-alpha dilauroyl-lysine methyl diethyleneglycolamide (1111KO2 or KO2) and its analogs with 4 or 6 ethylene glycol units (KO4 and KO6, respectively). The equilibrium and dynamic surface tensions of 0.1 wt.% dispersions of these compounds were studied at 37 and 25 degrees C, and were compared with those of DLPC and DLPC-KO2 (or KO4 or KO6) mixtures. The spread monolayer pressure-area isotherms were also determined. The equilibrium surface tensions of KO2 (or KO4, or KO6) are higher than those of DLPC. The DLPC-KO2 (or KO4 or KO6) mixtures have equilibrium and dynamic tension behavior closer to that of DLPC alone. The lack of a zwitterionic polar group produces a big difference in their surface activity, in part because of differences in their phase behavior. (C) 1997 Elsevier Science B.V.