  In order to study the viscoelastic properties of certain complex fluids which
are described in terms of a multiconnected transient network we have developed
a convenient model system composed of microemulsion droplets linked by
telechelic polymers. The phase behavior of such systems has two characteristic
features: a large monophasic region which consists of two sub-regions (a fluid
sol phase and a viscoelastic gel phase) separated by a percolation line and a
two phase region at low volume fraction with separation into a dilute sol phase
and a concentrated gel phase. From the plausible origin of these features we
expect them to be very similar in different systems. We describe here the phase
behavior of four different systems we prepared in order to vary the time scale
of the dynamical response of the transient network; they consist of the
combination of two oil(decane) in water microemulsions differing by the
stabilizing surfactant monolayer (Cetyl pyridinium chloride/octanol or
TX100/TX35) and of two telechelic polymers which are end-grafted poly (ethylene
oxide) chains, differing by the end-grafted hydrophobic aliphatic chains
(C12H25 or C18H37).
