  We study volume transition phenomenon in hydrogels within the framework of
Flory-Rehner thermodynamic modelling; we show that starting from different
models for the Flory parameter different conclusions can be achieved, in terms
of admissible coexisting equilibria of the system. In particular, with explicit
reference to a one-dimensional problem we establish the ranges of both
temperature and traction which allow for the coexistence of a swollen and a
shrunk phase. Through consideration of an augmented Flory-Rehner free-energy,
which also accounts for the gradient of volume changes, we determine the
position of the interface between the coexisting phases, and capture the
connection profile between them.
