  We present a new model of patchy particles in which the interaction sites can
be activated or deactivated by varying the temperature of the system. We study
the thermodynamics of the system by means of Wertheim's first order
perturbation theory, and use Flory-Stockmayer theory of polymerization to
analyse the percolation threshold. We find a very rich phase behaviour
including lower critical points and reentrant percolation.
