Mucus as an Arrested Phase Separation Gel

We investigate the spontaneous restructuring and aging behavior of pig gastric mucus gels by combining rheology and nonconventional static and dynamic light scattering. We find that the mucus elasticity weakens over time, concomitantly to structural evolution toward a locally more compact configuration and the onset of large scale density fluctuations. We interpret this behavior as stemming from an arrested phase separation, as observed in many gel-forming polymer systems. This scenario is confirmed by space and time resolved dynamic light scattering data, showing that the gel restructuring is due to intermittent bursts of spatially correlated rearrangements, leading to ballistic dynamics.