  By means of extensive equilibrium molecular dynamics simulations we have
investigated, the behavior of the interfacial tension $\gamma$ of two
immiscible symmetrical Lennard-Jones fluids. This quantity is studied as
function of reduced temperature $T^{*}={{k_{_B} T}\over \epsilon}$ in the range
$0.6 \leq T^{*} \leq 3.0$. We find that, unlike the monotonic decay obtained
for the liquid-vapor interfacial tension, for the liquid-liquid interface,
$\gamma (T)$ has a maximum at a specific temperature. We also investigate the
effect that surfactant-like particles has on the thermodynamic as well as the
structural properties of the liquid-liquid interface. It is found that $\gamma$
decays monotonically as the concentration of the surfactant-like particles
increases.
