Dynamics and kinetics of structure formation in molecularly tethered fluorocarbon/hydrocarbon amphiphiles

Biphasic fluorocarbon/hydrocarbon amphiphiles tethered to cores at distances commensurate with their packing requirement can provide thermodynamic pathways toward equilibrium. This contrasts with the analogous semifluorinated alkanes. The dynamics of a fluorous biphasic hexa(3,5-substituted-phenyl)benzene (HPB) is studied with dielectric spectroscopy as a function of temperature and pressure in comparison to the parent biphasic diphenylacetylene (DPA). Dielectric spectroscopy is a sensitive probe of the fluorocarbon environment through the end C-F dipole. Four dielectrically active processes were observed that associate with the CF₃ environment within the different phases (isotropic, liquid-like lamellar, solid lamellar, glassy state). Pressure facilitates the construction of the equilibrium phase diagram. The kinetic pathways to fluorocarbon organization are explored by pressure-jump experiments. A highly cooperative process was found that is atypical of a nucleation and growth process expected for first-order transitions.