Dual-functionalized cellulose nanofibrils prepared through TEMPO-mediated oxidation and surface-initiated ATRP

- Analyses have revealed the successful achievements of (i) nanosized cellulose nanofibers through surface TEMPO-oxidation; (ii) retained high molecular weights (MWs) of cellulose; and (iii) maintained the integrity of the cellulose crystallinity.
- The first example of a suitably oxidized TOCN functionalized with atom transfer radical polymerization (ATRP) initiating sites was conducted to overcome the obstacle of performing ATRP in the presence of neutral carboxylic acid sodium salt groups.
- Through surface-initiated ATRP from the TOCN with styrene, the fashion of controlled/living polymerization was confirmed by first-order kinetic plots, MW evolution, and low polydispersity, allowing control over the graft length and composition for being highly efficient at removing an organic pollutant and heavy metal ions from aqueous media.

Although several analogues of cellulose nanofibres displaying unprecedented physical properties have been developed recently (e.g., fibrillated cellulose nanofibrils; cellulose nanocrystals; bacterial nanocellulose; 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs)), only a few reports have described using these cellulose nanofibrils for advances in macromolecular engineering with the powerful tool of surface-initiated atom transfer radical polymerization (SI ATRP). In this paper, we describe the first example of a suitably oxidized TOCN that can be further functionalized with initiating sites at the residual primary OH groups and overcome the obstacle of performing ATRP in the presence of neutral carboxylic acid sodium salt groups. Characterization of the modified TOCNs and of the products from SI ATRP of the (nano)celluloses was performed using Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, viscometry, scanning electron microscopy, electron spectroscopy for chemical analysis, X-ray diffraction, contact angle measurements, and thermogravimetric analysis. We demonstrate, through SI ATRP from the TOCN using a vinyl monomer (i.e., styrene), a simple and facile approach for controlling the graft length and composition. We then investigated the efficacy of using the dual-functionalized TOCN nanomaterials to remove a commonly persistent organic pollutant and heavy metal ions from water.

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