ИСТИНА

It is well known that lecithin, a zwitterionic surfactant, can self- assemble into characteristic structures as spherical micelles and vesicles in water [1]. Addition of bile salt induces formation of elongated structures as ellipsoidal and cylindrical (rod-like) micelles [1]. Using computer simulation by means of dissipative particle dynamics (DPD) method [2], we have explored the effects of adding inorganic salt, as sodium chlorine (NaCl), to lecithin – bile salt mixtures in water. We take into account that the inorganic salt screens the ionic repulsions between the surfactant head groups and can promote the growth of ellipsoidal and cylindrical structures into long worm-like micelles. Such long flexible worm-like micelles can induce the increasing of viscosity of lecithin solution due to formation of cross-links between them, and this increasing of viscosity has been observed experimentally [1]. In our simulation, we have studied the influence of the molar ratio of bile salt to lecithin (B0) and of the inorganic salt concentration (c) on the formed structure. Quite dilute solutions have been studied where the volume fraction of lecithin and bile salt in the solution was equal to 0.1. We have found that cylinders start growing at the value B0=1. Addition of inorganic salt was taken into account in our model by decreasing of Flory-Huggins parameter between lecithin and bile salt, and decreasing of this value favors increasing of the length of cylindrical micelles.