Lignin nanoparticles with high interfacial activity and pickering emulsion stability prepared from hemp stem bark via a ‘one-pot’ method

Hemp straw bark, a high-yield renewable resource, faces sustainable development challenges due to underutilized lignin in traditional fractionation processes, often discarded as low-value waste. Herein, a one-pot strategy using choline chloride/lactic acid (ChCl/LA, 1:5) deep eutectic solvent (DES) enables controllable depolymerization and nanoscale self-assembly of lignin from it. Optimal conditions (solid-liquid ratio 1:80, 6 h) achieve a 98.6 % lignin yield relative to the initial lignin content in the raw material. FTIR and HSQC NMR confirm a selective β-O-4 ether bond cleavage with preserved aliphatic hydroxyls; 31 P NMR shows 3.1 mmol/g phenolic hydroxy and 1.28 mmol/g carboxy, enhancing interfacial activity. GPC reveals regulated molecular weights (M n 2160, M w 3632 g/mol, PDI = 1.68). Depolymerized lignin (L33) self-assembles into 190.1–220.2 nm nanoparticles (−32.5 mV zeta potential, good stability) with high thermostability (40 % char at 800 °C) and antioxidant activity (DPPH scavenging 73.9 % ± 1.1). LNPs (0.1 mg/mL) show potential as Pickering emulsion stabilizers, valorizing lignin into high-value materials. This study realized the effective and efficient separation of lignin from hemp straw bark, thereby offering a promising method for the industrial application of this lignin.