Sulfated Cellulose Nanofibrils from Chlorosulfonic Acid Treatment and Their Wet Spinning into High-Strength Fibers
Benjamin Pingrey, You‐Lo Hsieh
Abstract
This paper presents the proof of concept for a facile sulfation-disintegration approach toward generating sulfated cellulose nanofibrils (SCNF) via direct sulfation of rice straw cellulose with chlorosulfonic acid (HSO3Cl) followed by blending. The direct sulfation of cellulose with chlorosulfonic acid (HSO3Cl) was optimized at acid ratios of 1–1.5 HSO3Cl per anhydroglucose unit (AGU) and short reaction times (30–60 min) at ambient temperature to produce SCNF with tunable charges of 1.0–2.2 mmol/g, all in impressively high yields of 94–97%. SCNF were characterized via AFM, TEM, FTIR, and XRD. SCNF lengths (L: 0.75–1.24 μm) and widths (W: 3.9–5.9 nm) decreased with harsher sulfation, while heights (H: 1.23–1.32 nm) remained relatively static. The SCNF had uniquely anisotropic cross sections (W/H: 3.0–4.7) and high aspect ratios (L/H: 568–984) while also exhibiting amphiphilicity, thixotropy, and shear thinning behaviors that closely followed a power law model. Aqueous SCNF dispersions could be wet spun into organic and mixed organic/ionic coagulants, producing continuous fibers possessing an impressively high tensile strength and Young’s modulus of up to 675 ± 120 MPa and 26 ± 5 GPa, respectively.