(272h) Self-Assembly in Ternary Systems Containing Symmetric Amphiphilic Chains and Hybrid Organic-Inorganic Precursors

Porous functional materials can be obtained by self-assembly of surfactant and hybrid organic-inorganic precursors. The chemical nature of the precursor and the surfactant/inorganic ratio determines, to a large extent, the structure of the final material [1]. When inorganic condensation reaction can be decoupled from the formation of ordered phases, assuming that the reaction is slower than the self-assembly process, it is possible to assume that these systems can reach thermodynamic equilibrium.

In this work, we have calculated the phase behaviour of ternary systems containing a symmetric surfactant and simple representations of hybrid inorganic precursors. The effect of the hybrid organic-inorganic precursor can be similar to that observed in systems where cosurfactants and cosolvents are used [2]. The type of aggregates and their structure have been characterized by their shape and size (principal radii of gyration and aggregation number), as well as by their structure, calculating the composition profile of the aggregates when a well defined structure is obtained, or the radial distribution function when it is difficult to identify a priori the structure of the aggregates. When spherical aggregates are formed, increasing the hybrid precursor content decreases the number of surfactant chains in the aggregates. In the systems studied where self-assembled structures are observed, the hybrid precursors are located in the corona of the aggregates, and their concentration profile strongly depends on the precursor miscibility with the solvent. In systems where no ordered structures are obtained, the phase behaviour is well described by the quasichemical theory, but when ordered structures are obtained, the agreement is only qualitative.

[1]Hatton, B.; Landskron, K.; Whitnall, W.; Perovic, D.; Ozin, G. A. Accounts of Chemical Research 2005, 38, 305-312.

[2] N. Chennamsetty, H. Bock, L.F. Scanu, F.R. Siperstein, and K.E. Gubbins "Cosurfactant and cosolvent effects on surfactant self-assembly in supercritical carbon dioxide" J. Chem. Phys. 2005, 122, 094710