Comparative evaluation of physicochemical and structural properties of polyester-modified lignocellulose nanofibers...

Lignocellulosic nanofibers (LCNF) produced from different agricultural residues vary in crystallinity and non-cellulosic components, which significantly influence their dispersion behavior and interfacial interactions with hydrophobic polyesters. However, systematic comparisons of the grafting of poly lactic acid (PLA) and poly ε-caprolactone (PCL) onto LCNFs derived from multiple biomass under identical conditions remain limited. In this study, eight agricultural residues, e.g. sweet potato residues (SPR), sweet potato vines (SPV), potato residues (P), potato vines (PV), cassava residues (CA), cassava stalks (CAS), rice husks (RH), and maize stalks (MS) were selected. LCNFs were prepared via enzymatic-acid extraction-high pressure homogenization, followed by grafting with PLA and PCL through in-situ ring-opening polymerization (in-situ ROP). LCNF exhibited nanofibrillar morphologies with diameters of 5-30 nm and lengths of 0.5-2.0 μm, while showing clear source-dependent differences in crystallinity and chemical composition. SPR-LCNF showed the lowest crystallinity and the most negative ζ-potential, and achieved the highest grafting rates of 82.12% (PLA) and 85.68% (PCL). In contrast, RH- and MS-LCNFs displayed the lowest PLA grafting rates (51.30%-55.09%), consistent with their higher lignin and ash contents. Grafting altered thermal decomposition behavior, with T_max spanning 312.78-328.44 °C for PLA-grafted samples and 308.48-347.27 °C for PCL-grafted samples. Correlation analysis indicated that grafting efficiency decreased with increasing crystallinity in PLA and PCL systems and was further suppressed in lignin and ash-rich samples. Overall, this study provided guidance for selecting agricultural residues and understanding their effects on the grafting behavior of polyester-grafted LCNF.