  The stability of a thin liquid film bounded by two free surfaces is examined
in the presence of insoluble surface active agents. The surface active agents
not only cause gradients in surface tension, but could also render surface
viscosity to be significant, and variable, as a function of their
concentration. A set of three coupled nonlinear evolution equations are derived
for the film height, concentration of surface active agents, and the horizontal
liquid velocity which governs the dynamics of the free film. Suitable
phenomenological models for variation of surface tension and surface viscosity
with the concentration of surface active agents are incorporated in the
interfacial stress boundary condition. Linear stability analysis reveals the
effect of various non-dimensional parameters, specifically the retarding nature
of surface viscosity and Marangoni effects on film rupture. An analysis of the
`jamming' limit of surfactant concentration reveals that $\Gamma_0^{(nl)}<3
\mathbb{D}/M$ is a sufficient criteria for instability of the system, where
$\Gamma_0^{(nl)}$ is a normalized initial surface particle concentration,
$\mathbb{D}$ is the disjoining pressure number and $\textit{M}$ is the
Marangoni number. Nonlinear simulations suggest film profiles at rupture are
also qualitatively different from those reported in earlier studies, revealing
that free films in the jamming limit are remarkably stable and their free
surfaces behave like immobile interfaces. Furthermore, self-similar exponents
extracted from our nonlinear simulations are used to explain topological
differences between zero and constant surface viscosity in the vicinity of
rupture.
