Thermal and mechanical properties of dried foam films and their incorporation of water-soluble compounds.

Dried foam films (DFFs), which are free-standing reversed bilayers covering the holes of micrometers, are obtained by using several types of surfactants. In this article, we examined the formation of DFFs from a wide range of surfactants, systematically changing the headgroup, the counterion, the length and number of alkyl chains, and so forth. Some DFFs showed thermal stability higher than 150 degrees C. The interaction among headgroups in each monolayer of DFFs significantly contributed to the high thermal stability. The elastic moduli of DFFs were in the range of 4-42 MPa, as determined by a nanoindentation technique using AFM. A nonionic surfactant (Brij-35) formed stable DFFs only when urea was incorporated to form hydrogen bonds with the ethylene oxide units. The thermal stability of DPC (dodecylphosphocholine) films was increased up to 220 degrees C by adding Cd(2+) because of the formation of a coordination network with the phosphate groups. Then the elastic modulus increased from 15 to 32 MPa. It was also possible to incorporate polyelectrolytes (Na(2)SiO(3) and PAH) and a cadmium polynuclear complex ([Cd(10)(SCH(2)CH(2)OH)(16)] x (ClO(4))(4)) into the interlayer space of DFFs by tuning the proximal electrostatic interaction with the headgroups of surfactants.