Supramolecular assembly and surfactant behavior of triblock rod-coil amphiphiles at liquid interfaces using classical density functional theory

In the framework of Wertheim's perturbation theory we present a classical density functional theory for rod-coil molecules with one rigid block and one or two flexible blocks. The theory is validated against molecular simulation for the case of an amphiphilic molecule in a selective pore. The theory is then applied to study the interfacial properties of the oil-water interface in the presence of triblock rod-coil amphiphiles (TBRCA's) consisting of a center rigid hydrophobic rod portion with flexible hydrophilic tails attached to each end. It is shown that TBRCA's preferentially adsorb to the interface in either a parallel or perpendicular orientation. The fraction of TBRCA's in each orientation can be manipulated by varying the length of the flexible hydrophilic tails, temperature, length of the hydrophobic rod or the total number of TBRCA's at the interface. Also it is shown that the structural properties of TBRCA's can be adjusted to yield a broad range of surfactant behavior.