  Low-density networks of molecules or colloids are formed at low temperatures
when the interparticle interactions are valence limited. Prototypical examples
are networks of patchy particles, where the limited valence results from highly
directional pairwise interactions. We combine extensive Langevin simulations
and Wertheim's theory of association to study these networks. We find a
scale-free (relaxation) dynamics within the liquid-gas coexistence region,
which differs from that usually observed for isotropic particles. While for
isotropic particles the relaxation dynamics is driven by surface tension
(coarsening), when the valence is limited, the slow relaxation proceeds through
the formation of an intermediate non-equilibrium gel via a geometrical
percolation transition in the Random Percolation universality class.
