Regioselectively Carboxylated Cellulose Nanofibril Models from Dissolving Pulp: C6 via TEMPO Oxidation and C2,C3 via Periodate–Chlorite Oxidation

Abstract

Regioselective C6 and C2,C3 carboxylated cellulose nanofibrils (CNFs) have been robustly generated from dissolving pulp, a readily available source of unmodified cellulose, via stoichiometrically optimized 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO)-mediated and sequential sodium periodate-sodium chlorite (PC) oxidation coupled with high-speed blending. Both regioselectively optimized carboxylated CNF series possess the widest ranges of comparable charges (0.72–1.48 mmol/g for T-CNFs vs. 0.72–1.10 mmol/g for PC-CNFs), but similar ranges of thickness (1.3–2.4 nm for T-CNF, 1.8–2.7 nm PC-CNF), widths (4.6–6.6 nm T-CNF, 5.5–5.9 nm PC-CNF), and lengths (254–481 nm T-CNF, 247–442 nm PC-CNF). TEMPO-mediated oxidation is milder and one-pot, thus more time and process efficient, whereas the sequential periodate–chlorite oxidation produces C2,C3 dialdehyde intermediates that are amenable to further chemical functionalization or post-reactions. These two well-characterized regioselectively carboxylated CNF series represent coherent cellulose nanomaterial models from a single woody source and have served as references for their safety study toward the development of a safer-by-design substance evaluation tool.

Aqueous exfoliation and dispersion of monolayer and bilayer graphene from graphite using sulfated cellulose nanofibrils

“…Therefore, SCNF are expected to have similar ability to interact with graphene ( via similar proportions of exposed hydrophobic planes) but may exhibit varied charge-dependent aqueous dispersibilities. This SCNF series also provides a range of well represented C6 sulfated CNFs along with C6 and C2/C3 carboxylated CNFs by respective TEMPO and periodate–chlorite oxidation of the same dissolving pulp 26 toward the development of a toolbox of safer by design substance evaluation tools linking the biological behavior of functionalized CNFs to their surface chemistries, charges, and dimensions. 27…”

In-Depth Understanding of the Effect of the Distribution of Substituents on the Morphology and Physical Properties of Ethylcellulose: Molecular Dynamics Simulations Insights

“…Other regioselectively modified cellulose include TEMPO-oxidized cellulose (at carbon C6) and dialcohol cellulose (with broken C2−C3 bonds). 8,9 Ethylcellulose (EC) is a cellulose derivative that has been utilized in pharmaceutical formulations, 10,11 heat-resistant chocolates, 12 films, 13 food packaging, 14 ink formulations, 15,16 etc., owing to its attributes such as being hydrophobic, lightstable, heat-resistant, and with the ability to stabilize dispersions. With these desirable properties, EC can be used as an excipient in various pharmaceutical formulations to enable production by, for example, being used as an additive in wet granulation liquids or to control the formulation properties, like masking the taste or controlling the drug release rate.…”

“…They also observed that the regioselectively substituted compounds were soluble in water, whereas randomly substituted compounds were insoluble. Other regioselectively modified cellulose include TEMPO-oxidized cellulose (at carbon C6) and dialcohol cellulose (with broken C2–C3 bonds). , …”

“…Other regioselectively modified cellulose include TEMPO-oxidized cellulose (at carbon C6) and dialcohol cellulose (with broken C2–C3 bonds). 8 , 9 …”