Supramolecular Jamming Transition in Concentrated Methacrylated Kraft Lignin Solutions: Rheological Scaling Laws for High-Loading Reactive Resins

Maximizing renewable carbon in reactive polymer resins is bottlenecked by viscosity of lignin-containing systems. We targeted the unentangled, ethyl acetate-soluble fraction of methacrylated Kraft lignin (ML-f) and formulated it in diethyl fumarate (DEF), a thermodynamically matched, bio-derived reactive diluent, yielding homogeneous solutions containing up to 60 wt % lignin. Through steady-shear and thermodynamic analyses, we defined the limit of room-temperature processability: a supramolecular jamming transition at [ML-f]* ≈36.5 wt %. Below this threshold, viscosity scales moderately (ν = 2.69), consistent with unentangled polymer solutions. Above it, viscosity diverges catastrophically (ν = 13.41), with an apparent activation energy of 74.5 kJ/mol at 60 wt %. Time−Temperature Superposition confirms the jammed state is thermorheologically simple, governed by reversible π−π stacking rather than permanent crosslinks. Moderate heat (45 °C) unlocks flow, and photo-patterning confirms dispersion below the colloidal scattering threshold. These scaling laws establish the physical framework for rational formulation of high-loading lignin-based reactive resins.