Effect of hard confinement on the phase state and dynamics of 1-propanol/water mixtures

Abstract

1-propanol/water mixtures are structurally and dynamically heterogeneous over several length and time scales. Their phase diagram comprises liquid droplet phases of 1-propanol or water, as well as crystalline phases (hexagonal ice and different hydrates). We study the effect of hard confinement on the phase state and dynamics of 1-propanol/water mixtures. The mixtures were confined within self-ordered nanoporous alumina templates having long cylindrical nanopores. We show that the remote hard interface influences the phase state and the molecular dynamics. In the propanol-rich regime, where water exists in droplets, water could be supercooled below the homogeneous nucleation temperature and well within “no man’s land” where water crystallizes rapidly. Within the water-rich regime, the remote interface breaks the 1-propanol chain-like hydrogen bonded assemblies as reflected in the suppression of the Debye process. Calculation of the Hamaker constants provided quantitative information on distant intermolecular forces and their role in the structure and dynamics.