The preparation and properties of bamboo lignocellulosic nanofibers based on deep eutectic solvent system

<p indent="0mm">In this study, by designing four lactic acid (LA)-based DES systems (DES1: 2-mercaptopropionic acid/LA; DES2: 3-mercaptopropionic acid/LA; DES3: L-alanine/LA; and DES4: L-cysteine/LA), a systematic study was carried out to investigate the mechanisms of the types of groups (–OH, –NH₂, and –SH) and their steric effects on the pretreatment and preparation of lignocellulosic nanofibers (LCNF). The DES1, DES2, and DES4 systems, containing –SH groups, exhibited excellent separation ability during the pretreatment process, significantly enhancing the removal of lignin and hemicellulose while effectively retaining cellulose. Notably, the DES4 system demonstrated the best pretreatment effect due to the synergistic effect of the –NH₂ and –SH groups in L-cysteine, resulting in the highest LCNF yield, the best thermal stability, and good dispersion and stability of the LCNF. In contrast, the DES3 system showed an inferior pretreatment effect, lower LCNF yield, and performance, due to the alkaline property of the –NH₂ group that reduced the acidity of the system. Additionally, molecular dynamics simulations revealed the microscopic mechanism of interaction between hydrogen bonding properties (including the number of hydrogen bonds, bond angles, and bond lengths) and the interaction energies between the fibers and the pretreatment system, as well as the diffusion coefficients of the cellulose into DES systems.