ARRESTED-VOLUME PHASE-TRANSITION OF A GEL AROUND A HOLE

When there is a hole in a chemically cross-linked gel, the phase trans ition from swollen to shrunken phase starts at the free surface of the hole. The growth of the new phase is, however, arrested eventually ar ound the hole with a finite thickness depending on controlling paramet ers such as temperature. This phenomenon is in strong contrast with th e condensation of vapour under constant pressure, and exemplifies the inapplicability of Gibbs's phase rule to coherent solids. We give a qu alitative argument for it and then demonstrate it by a simple model ca lculation.