A molecular theory of the surface tension of surfactant solutions

摘要: Abstract Through the experimental investigations carried out by Motomura and co-workers it has been shown that for surfactant solution/air interfaces there is generally a Henry's law region at low concentrations ( c = 0.1 c.m.c. first-order surface phase transition occurs (corresponding with breakpoint in tension versus concentration curve) which results formation of condensed monolayer liquid-expanded type. Upon raising further range above (0.1 −1 . In order to account data this kind obtained et al. dodecylammonium chloride (C 12 NH + 3 Cl − ) solutions, we have modelled assuming following excess free energy contributions: (i) change associated transferring hydrocarbon chain from water liquid as quantified Tanford; (ii) electrostatic computed according Gouy—Chapman theory; (iii) configurational chains statistical mechanical calculations Gruen; (iv) hydrocarbon/water contact was set equal its macroscopic value oil/water (∼ 50 mJ m −2 ). The resulting computation scheme also includes options dodecyl alcohol OH) salt present solution. monolayer—solution equilibrium established means numerical iteration procedures. Satisfactory agreement demonstrated γ C 2 implying main contributions lowering (mechanical) are pressure (below about A /chain) packing-dependent layer. Furthermore, on basis can propose between gaseous state (stretched) (which gives rise step-isotherm) hydrophobically driven. addition, calculation concerning effects adding OH presented penetration an insoluble be readily analyzed molecular terms employing our theoretical approach.