Extraction, characterization and chemical functionalization of phosphorylated cellulose derivatives from Giant Reed Plant

In this work, cellulose microfibers (CMFs) and cellulose nanocrystals (P-CNCs) having phosphoric groups on their surfaces were prepared by phosphorylation of cellulose extracted from Giant Reed plant, using ammonium dihydrogen phosphate (NH₄H₂PO₄) in a water-based urea system and phosphoric acid (H₃PO₄) without urea as phosphorous agents, respectively. Phosphorylated samples were studied in terms of their charge content, chemical structure, crystallinity, morphology, and thermal stability using several characterization techniques. Conductometric titration results showed higher charge content after phosphorylation with urea for P-CMFs about 3133 mmol kg⁻¹, while without urea P-CNCs exhibited 254 mmol kg⁻¹. FTIR analysis confirmed the total removal of non-cellulosic compounds from microfibers’ surface and their partial oxidation after phosphorylation. XRD analysis proved that the P-CMFs and P-CNCs exhibited cellulose I structure, with a crystallinity index of 70 and 83%, respectively. SEM and AFM observations showed micro-sized and needle-like morphologies for P-CMFs and P-CNCs with an average diameter of 15 µm and 20.5 nm, respectively. The thermal properties of P-CMFs indicate early dehydration with high char formation, while the high thermal stability of P-CNCs (T_max = 352 °C) was similar to that of microcrystalline cellulose. The present work showed new routes for preparing phosphorylated micro- and nano-cellulose from a new natural source, having new functions that benefit various applications.