Understanding the Mechanistic Behavior of Highly Charged Cellulose Nanofibers in Aqueous Systems

Abstract

Mechanistic behavior and flow properties of cellulose nanofibers (CNFs) in aqueous systems can be described by the crowding factor and the concept of contact points, which are functions of the aspect ratio and concentration of CNF in the suspension. In this study, CNFs with a range of aspect ratio and surface charge density (380–1360 μmol/g) were used to demonstrate this methodology. It was shown that the critical networking point of the CNF suspension, determined by rheological measurements, was consistent with the gel crowding factor, which was 16. Correlated to the crowding factor, both viscosity and modulus of the systems were found to decrease by increasing the charge density of CNF, which also affected the flocculation behavior. Interestingly, an anomalous rheological behavior was observed near the overlap concentration (0.05 wt %) of CNF, at which the crowding factor was below the gel crowding factor, and the storage modulus (G′) decreased dramatically at a given frequency threshold. This behavior is discussed in relation to the breakup of the entangled flocs and network in the suspension. The analysis of the mechanistic behavior of CNF aqueous suspensions by the crowding factor provides useful insight for fabricating high-performance nanocellulose-based materials.

Alcohol induced gelation of TEMPO-oxidized cellulose nanofibril dispersions

“…These oxidized cellulose nanofibrils (OCNFs) are anionic particles and form stable dispersions of individualized nanofibrils in water. [20][21][22] OCNFs can selfassemble in an aqueous environment due to the influence of concentration, 23 OCNF aspect ratio, 24 co-solutes, such as surfactants, 16 salts, 9,25,26 or block copolymers 27 as well as pH. [28][29][30] This flexibility makes OCNFs a good choice as building blocks in self-assembled hydrogels.…”

Rheology of Dispersions of High-Aspect-Ratio Nanofibers Assembled from Elastin-Like Double-Hydrophobic Polypeptides

“…Despite the aforementioned differences in nanofiber structures, GPG and GPPG behaved similarly in rheological experiments except for the poor reproducibility in frequency sweep measurements for GPG ( Figure 6). The steep drop in G' that was seen at higher frequencies, which was most probably due to a change in the nanostructure of the dispersion, was detected in other nanofiber dispersion systems [39]. GPG nanofibers may be locally aggregated in a dispersion, as suggested by the TEM observation (Figure 5a), which causes a slight sample-to-sample variation in the rheological readings.…”

“…The viscoelastic properties that were presented in this paper were also uncommon among other fiber dispersion systems to the best of our knowledge. For example, Hsiao, Söderberg, and coworkers reported on the mechanistic behavior of charged cellulose nanofibers (CNF) in aqueous systems [39]. The dispersion behaved solid-like (G' > G") at 0.1 wt% nanofiber concentration with G' of ca.…”

Explaining the Exceptional Wet Integrity of Transparent Cellulose Nanofibril Films in the Presence of Multivalent Ions—Suitable Substrates for Biointerfaces

“…The estimated aspect ratio was measured to be 400–480 for medium charge TO‐CNFs and has previously been determined to be 200–250 for high charge TO‐CNFs . An increase in the degree of TEMPO‐oxidation leads to a degradation of the cellulose macromolecules, which in turn results in shorter fibrils . Short fibrils reduce the stress transfer within the CNF network and hence lead to a weaker material.…”

“…Short fibrils reduce the stress transfer within the CNF network and hence lead to a weaker material. The fibril dimensions have previously been shown to influence the mechanical properties of dry films and the viscosity of dispersions prepared from TO‐CNFs …”