Molecular engineering of lignin toward Organic-Inorganic Shell-Core Nano–Hybrids for High–Performance Styrene-Butadiene rubber composites

Owing to the growing interest in lignin-derived hybrid fillers for biomass valorization and sustainable rubber applications, molecular engineering of lignin has emerged as an effective strategy. This work designed a versatile organic–inorganic nano-hybrid via the in-situ assembly of quaternized lignin (Q n L) and SiO 2 . Lignin was first quaternized yielding a series of Q n L with tunable grafting content (4.40–17.95 wt%). Driven by electrostatic interactions, Q n L and SiO 2 assembled into shell-core structured nanohybrids (Q n LSi), exhibiting a denser packing morphology and higher hydrophobicity compared to the unmodified lignin/SiO 2 reference. These structural characteristics promoted uniform dispersion of hybrid particles when incorporated into styrene-butadiene rubber (SBR) via latex mixing. The hybrids with a higher degree of lignin quaternization enabled the SBR vulcanizates to achieve improved vulcanization efficiency ( t 90 reduced from 21.90 to 13.16 min), enhanced mechanical properties (tensile strength increased from 24.2 to 29.5 MPa) and reduced dynamic losses (tan δ 60 °C decreased from 0.111 to 0.104). This superior performance stems from the small particle size, favorable surface functionalities and strong rubber-filler affinity. Overall, this study highlights the molecular engineering strategy to shape lignin into multifunctional hybrids for high-performance, energy-efficient, and sustainable rubber materials.