EFFECT OF LIPID PHASE STATE AND FOAM FILM TYPE ON THE PROPERTIES OF DMPG STABILIZED FOAMS

The drainage and stability of DMPG (L-alpha-phosphatidyl-DL-glycerol d imyristoyl) foams were studied by a microconductivity method under con ditions where three different foam film types could be formed-thin foa m films (TFF), common black foam films (CBF), and Newton black foam fi lms (NBF). Foaming properties were investigated at 20 and 28 degrees C where DMPG is in the gel and liquid-crystalline states. Higher conduc tivity signals were observed at the higher temperature where DMPG was in the liquid-crystalline state, which is indicative of wetter or more stable foams under these conditions. This effect was observed indepen dent of foam film type. However, for a given phase state, the type of foam films formed significantly influenced the stability and rate of d rainage of the foam. Indeed, the water content of the foams, obtained under conditions for formation of different foam films, is ranked in t he order TFF > CBF > NBF. When the temperature was increased to 28 deg rees C (i.e., in the liquid-crystalline state), CBF and NBF showed a s light decrease in film thickness and an increase in film lifetime and surface molecular diffusion coefficient in the adsorbed layer. It is l ikely that the fluidity of the interfacial layer is an important facto r contributing to DMPG foam stabilization. (C) 1997 Academic Press.