Controlling interfacial film formation in mixed polymer-surfactant systems by changing the vapor phase.

摘要: Here we show that transport-generated phase separation at the air-liquid interface in systems containing self-assembling amphiphilic molecules and polymers can be controlled by relative humidity (RH) of air. We also our observations described quantitatively with a theoretical model describing interfacial water gradient published previously. These phenomena arises from fact chemical potential corresponding to ambient RH will, general, not match open aqueous solution. This implies nonequilibrium conditions air-water interface, which turn have consequences on molecular organization this layer. The experimental setup is such control boundary thereby verify predictions model. polymer-surfactant studied here are composed polyethylenimine (PEI) hexadecyltrimethylammonium bromide (CTAB) or didecyldimethylammonium (DDAB). Grazing-incidence small-angle X-ray scattering results phases hexagonal lamellar structure form dilute micellar solutions. From spectroscopic ellipsometry data conclude variations used growth micrometer-thick films reducing leads thicker films. For CTAB-PEI system, compare behavior equilibrium bulk behavior. film resembles formed high surfactant polymer ratio reduced contents, predict composition phase. convection vapor strongly reduces formation, likely due reduction unstirred layer, where diffusive transport dominating.