Susceptibility of I_α- and I_β‑Dominated Cellulose to TEMPO-Mediated Oxidation

The susceptibility of I_α- and I_β-dominated cellulose to TEMPO-mediated oxidation was studied in this work since the cellulose I_α-allomorph is generally considered to be thermodynamically less stable and therefore more reactive than the cellulose I_β-allomorph. Highly crystalline Cladophora nanocellulose, which is dominated by the I_α-allomorph, was oxidized to various degrees with TEMPO oxidant via bulk electrolysis in the absence of co-oxidants. Further, the Cladophora nanocellulose was thermally annealed in glycerol to produce its I_β-dominated form and then oxidized. The produced materials were subsequently studied using FTIR, CP/MAS ¹³C NMR, XRD, and SEM. The solid-state analyses confirmed that the annealed Cladophora cellulose was successfully transformed from an I_α- to an I_β-dominated form. The results of the analyses of pristine and annealed TEMPO-oxidized samples suggest that I_α- and I_β-dominated cellulose do not differ in susceptibility to TEMPO-oxidation. This work hence suggests that cellulose from different sources are not expected to differ in susceptibility to the oxidation due to differences in allomorph composition

Surface Modified Nanocellulose Fibers Yield Conducting Polymer-Based Flexible Supercapacitors with Enhanced Capacitances

We demonstrate that surface modified nanocellulose fibers (NCFs) can be used as substrates to synthesize supercapacitor electrodes with the highest full electrode-normalized gravimetric (127 F g^–1) and volumetric (122 F cm^–3) capacitances at high current densities (300 mA cm^–2 ≈ 33 A g^–1) until date reported for conducting polymer-based electrodes with active mass loadings as high as 9 mg cm^–2. By introducing quaternary amine groups on the surface of NCFs prior to polypyrrole (PPy) polymerization, the macropore volume of the formed PPy-NCF composites can be minimized while maintaining the volume of the micro- and mesopores at the same level as when unmodified or carboxylate groups functionalized NCFs are employed as polymerization substrates. Symmetric, aqueous electrolyte-based, devices comprising these porosity-optimized electrodes exhibit device-specific volumetric energy and power densities of 3.1 mWh cm^–3 and 3 W cm^–3 respectively; which are among the highest values reported for conducting polymer electrodes in aqueous electrolytes. The functionality of the devices is verified by powering a red light-emitting diode with the device in different mechanically challenging states