Streamlined Synthesis of Sulfated Cellulose Nanofibrils using Chlorosulfonic Acid and Their Applications in Conducting Materials

Cellulose nanofibrils (CNF) are one-dimensional semicrystalline nanomaterials liberated from native cellulose through chemical or mechanical processes, or some combination thereof. Individually, they possess high mechanical strength, with estimated tensile strength and Young’s modulus as high as 7.5 GPa and 150 GPa, respectively. They also serve as a diverse platform for further chemical modification due to their abundant surface hydroxyl groups, which can be functionalized through a wide array of chemical reactions. Isolating CNF from cellulose can be an energy intensive process and chemical pretreatments are often utilized to reduce the required energy expenditure.Herein a streamlined scheme for producing sulfated cellulose nanofibrils (SCNF) is proposed and optimized, utilizing chlorosulfonic acid to simultaneously functionalize cellulose while also acting as a pretreatment to facilitate defibrillation into nanofibrils. Through careful manipulation of reaction conditions, SCNF are produced with a wide range of sulfation levels without destroying the underlying cellulose 1β crystalline structure. Utilizing wet-spinning, SCNF was spun into fibers with a tensile strength and Young’s modulus of 675 MPa and 26 GPa, respectively. It was also demonstrated that SCNF could serve as host polyelectrolytes for the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) to create dispersible polyelectrolyte complexes, with shear-mediated alignment of nanofibrils allowing for the creation of fibers with a conductivity of more than 6000 S/cm. Additionally, SCNF were able to aid in aqueous exfoliation of graphite flakes and dispersion of graphene, producing exclusively monolayers and bilayers