Articles you may be interested inSmall-angle neutron-scattering study on a structure of microemulsion mixed with polymer networks Small angle neutron scattering near the wetting transition: Discrimination of microemulsions from weakly structured mixtures Small angle neutron scattering near Lifshitz lines: Transition from weakly structured mixtures to microemulsions Microemulsions are colloidal systems which are made by a dispersion of minute droplets (a few hundred A in diameter) of one component (e.g. water) in a continuous medium formed by another immiscible component (e.g. oil); the droplets are surrounded by a mixed film of surfactants. New information has been obtained about the distribution of the various components in the elementary droplet. The hydrodynamical interface is shown to contain an important amount of the continuous phase and a quantity of alcohol which increases with the amount of solubilized water. In contrast. the corresponding variation of the area per polar head of the surfactant molecule is relatively small. Small angle neutron scattering indicates that a portion of the interfacial film, 9 A thick, is not penetrated by the oily phase. The droplets are weakly correlated.
The development of porous films presenting accessible high specific surface area is important to design new adsorbents, sensors or catalyst supports. Here, we describe a simple method to prepare a foam silica coating by using an evaporation induced emulsification method assisted by calcium chloride. An alcoholic silica sol containing calcium chloride and a poly(ethylene oxide) containing polymer is deposited on a substrate by dip-coating. The alcohol evaporation induces a phase separation between a silica-rich phase and a calciumrich one. The droplets size increases via a coalescence process until the sol gelation, which determines the final pore size comprised between 100 nm and 3 µm. Thermal analysis and droplet evaporation monitoring both confirm that the solvent departure is delayed by the presence of calcium chloride into the sol. Influence of the polymer nature on the porosity is discussed. Using a block copolymer such as the Pluronic F-127, which strongly stabilizes the emulsion, allows to reach a low pore size (400 nm) while on the opposite, we propose to use a short poly(ethylene glycol) (PEG) such as the PEG-400, which weakly stabilizes it, leading 2 to larger pores (2-3 microns). Moreover, we show that adding a zirconium salt (ZrOCl 2 .8H 2 O) into the silica sol speeds up the condensation step of the silica network and leads to the decreasing in the pore size.
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