Phospholipid black foam films: dynamic film tension of DMPC bilayer films

The film tension of bilayer Newton black films (NBF) from aqueous dispersions of dimyristoylphosphatidylcholine (DMPC) has been studied in dynamic conditions. The dynamic film tension values γ have been measured using the capillary method for direct measurement of the film tension. Two different solutions have been used: DMPC vesicle suspension in water obtained through sonication, denoted as ‘DMPC(Son)’ (the DMPC adsorption layers are insoluble monolayers) and DMPC dissolved in ethanol plus water mixed solvent, denoted as ‘DMPC(EthW)’ (the DMPC adsorption layers are soluble). Both solutions contain 0.1 M NaCl. The behavior of the dynamic film tension is different for NBF from the two types of solutions. In the case DMPC(Son) γ strongly depends on the film area, while in the case DMPC(EthW) this dependence is less pronounced but still exists. The dependence of the film tension on the film area in case DMPC(Son) is well described by the Frumkin equation modified for bilayer films. Reasonable values of the parameters of Frumkin equation are determined from its fit to the experimental data.