1 research outputs found
Nanoconfinement-Induced Phase Segregation of Binary Benzene–Cyclohexane Solutions within a Chemically Inert Matrix
Binary
solutions provide a fertile arena to probe intermolecular
and molecular/surface interactions under nanoconfinement. Here, the
phase segregation of a solution comprising 0.80 mol fraction benzene
and 0.20 mol fraction cyclohexane confined within SiO<sub>2</sub> nanopores
was evaluated using small-angle neutron scattering with hydrogen–deuterium
contrast matching. It is demonstrated that benzene and cyclohexane
are fully miscible at 303 K (30 °C), yet they unambiguously phase
segregate by 153 K (−120 °C), which is below their respective
freezing points and below the cubic-to-monoclinic phase transition
of cyclohexane. Specifically, the cyclohexane and benzene separate
into a core|shell morphology with cyclohexane concentrated toward
the nanopore centers. Additionally, pure benzene is shown to form
a frozen core of bulk density with a thin shell of slightly reduced
density immediately adjacent to the SiO<sub>2</sub> nanopore wall
at 153 K. Because the SiO<sub>2</sub> matrix is chemically inert to
cyclohexane and benzene, the observed radially dependent phase segregation
is strong evidence for the effects of confinement alone, with minimal
host–wall attraction