Aging of the linear viscoelasticity of glass- and gel-forming liquids

Glasses and gels are amorphous materials that experience dynamical arrest, preventing them from reaching thermodynamic equilibrium within experimentally accessible times. This leads to a slow and long-lasting evolution of their structural, dynamical and rheological properties after preparation, a phenomenon referred to as aging that remains far from being fully understood. Here we discuss a novel theoretical scheme that facilitates the description and interpretation of experimental data concerning the out-of-equilibrium rheological behavior of viscous liquids during their amorphous solidification. The predictive capability of our approach is illustrated here through quantitative comparisons of theoretical and experimental results for the linear viscoelastic properties of different glass-and-gel-forming materials, finding an almost perfect correspondence.