Agarose gelation beyond equilibrium through distributed kinetic pathways and apparent thermodynamic signatures

The gelation of agarose in aqueous solution is studied by differential scanning calorimetry (DSC) under non-isothermal cooling at different rates. The thermograms show a clear exothermic peak whose position and shape depend on the cooling rate, highlighting the coupling between the imposed thermal protocol and the intrinsic timescales of network formation. The sol–gel transition is described through a temperature- and rate-dependent degree of transformation, defined as the normalized fraction of exchanged enthalpy. This model-free parameter yields sigmoidal conversion curves that progressively shift and distort at higher cooling rates, indicating a deviation from quasi-equilibrium conditions. Extrapolation to zero cooling rate identifies a unique gelation temperature, independent of protocol and conversion level, thereby providing an operational gel point. The derivative of the conversion yields a kinetic profile whose broadening at high rates reflects cooperative, distributed, non-equilibrium gelation dynamics.