  Signatures of glassy dynamics have been identified experimentally for a rich
variety of materials in which molecular networks provide rigidity. Here we
present a theoretical framework to study the glassy behavior of both passive
and active network materials. We construct a general microscopic network model
that incorporates nonlinear elasticity of individual filaments and steric
constraints due to crowding. Based on constructive analogies between structural
glass forming liquids and random field Ising magnets implemented using a
heterogeneous self-consistent phonon method, our scheme provides a microscopic
approach to determine the mismatch surface tension and the configurational
entropy, which compete in determining the barrier for structural rearrangements
within the random first order transition theory of escape from a local energy
minimum. The influence of crosslinking on the fragility of inorganic network
glass formers is recapitulated by the model. For active network materials, the
mapping, which correlates the glassy characteristics to the network
architecture and properties of nonequilibrium motor processes, is shown to
capture several key experimental observations on the cytoskeleton of living
cells: Highly connected tense networks behave as strong glass formers; intense
motor action promotes reconfiguration. The fact that our model assuming a
negative motor susceptibility predicts the latter suggests that on average the
motorized processes in living cells do resist the imposed mechanical load. Our
calculations also identify a spinodal point where simultaneously the mismatch
penalty vanishes and the mechanical stability of amorphous packing disappears.
