Molecularly tethered amphiphiles as 3-D supramolecular assembly platforms: unlocking a trapped conformation

A fluorous biphasic hexa(3,5-substituted-phenyl)benzene (HPB), analogous to semifluorinated alkanes, was synthesized such that precise chemical and orthogonally directed, supramolecular placement of amphiphilic side chains at their bulk density was achieved. The grafting or tethering of incommensurate hydrocarbon and fluorocarbon chains to the rotationally flexible HPB core inextricably links intermolecular phase separation with intramolecular conformational behavior and results in rich self-assembly. The self-assembled structure was studied with polarized optical microscopy, differential scanning calorimetry, X-ray scattering, and (19)F magic-angle spinning solid-state NMR and found to be kinetically trapped with mixed fluorocarbon and hydrocarbon side chains, despite packing into a lattice defined by the HPB scaffold. The addition of 1% of the parent biphasic diphenylacetylene unlocks the frustrated conformation in the HPB, resulting in the formation of a thermodynamically favorable bilayer structure.