Effect of hydrocarbon incorporation in the RH12A(EO)9 system: Preparation of porous materials

We have investigated the preparation, in a direct one-step reaction, of mesoporous and/or macroporous silica materials from the RH12A(EO)9 surfactant-based system. We have to look at the phase behavior of the RH12A(EO)9 surfactant in water as well as the effect of the solubilization of various hydrocarbons in this system. The phase diagram proved that hexadecane, decane and cyclohexane can be incorporated into the micelles (L1). Results also show that whatever the liquid crystal phases [direct hexagonal (H1) and lamellar (Lα)] both the swelling and the penetration effects take place upon addition of decane, while only the swelling effect occurs with hexadecane. Moreover, for these two hydrocarbons, at high oil concentration, oil-in-water concentrated emulsion is formulated. The stability of the emulsion is enhanced from days to several weeks with the addition of oil.Starting from the various systems, porous silica materials were then synthesized. The present work shows that in contrary to cyclohexane, hexadecane and decane are effective expanders for the mesopore size enlargement. This suggests that in the micelles hexane and decane form a core of oil, whereas cyclohexane is incorporated between the hydrophobic chains of the surfactant. The variations of the pore diameter upon the addition of oil have been related to the solubilization properties of the oil in the surfactant. Our study also reveals that hydrogenated systems behave as the fluorinated ones, i.e., the formation of macroporous materials templated by emulsions is favored with systems, which exhibit a high value of the PIT.