The transition from the dynamics of isolated molecules to that of a bulk liquid is observed for the first time by analyzing the dielectric relaxation $({10}^{-2\mathrm{}}–{10}^9\mathrm{Hz})$ of ethylene glycol (EG) guest molecules confined to zeolitic host systems of different topology. Beyond a threshold channel size the liquid character is lost, indicated by a dramatically increased relaxation rate and an Arrhenius-like temperature dependence. Computer simulations of the molecular arrangement in a confining space prove that an ensemble as small as six molecules is sufficient to exhibit the dynamics of a bulk liquid.

• Received 15 September 1998

DOI:https://doi.org/10.1103/PhysRevLett.82.2338