Phosphorylated cellulose nanofibrils from sugarcane bagasse with pH tunable gelation

A facile strategy is reported to convert sugarcane bagasse (SCB) cellulose into phosphorylated cellulose nanofibrils (PCNFs) whose gelation is pH-dependent via the different ionic forms of phosphoric groups (H2PO4−, HPO4−2, PO4−3). Cellulose was isolated from SCB at a 42.1% yield, then phosphorylated at an optimized 1:0.5:2 anhydroglucose (AHG)/(NH4)2HPO4/CO(NH2)2 molar ratio and, at pH 12, was in the most charged phosphate (PO4−3) to be disintegrated to generate 84.3% PCNFs. PCNFs were 3.84 nm wide, 0.73 nm high, up to 500 nm long, and highly charged (2.56 mmol g−1). Aqueous PCNF exhibited strongly pH-dependent gelation, gelling at 1.4 wt.% at pH 12 and at lowered 1.0 and 0.8 wt% at pH 7 and 2, respectively, enabling potential applications in full range of pH.