Versatile Surface Modification of Cellulose Fibers and Cellulose Nanocrystals through Modular Triazinyl Chemistry

Abstract

The ability to tune the interfacial and functional properties of cellulose nanomaterials has been identified as a critical step for the full utilization of nanocellulose in the development of new materials. Here, we use triazine chemistry in a modular approach to install various functionalities and chemistries onto cellulose fibers and cellulose nanocrystals (CNCs). The surface modification is demonstrated in aqueous and organic media. Octadecyl, monoallyl-PEG, benzyl, and propargyl triazinyl derivatives were grafted onto cellulose/ CNCs via aromatic nucleophilic substitution in the presence of base as hydrochloric acid scavenger. The covalent nature and degree of substitution of grafted aliphatic, polymeric, alkyne chains, and aromatic rings were characterized through Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, elemental analysis, and thermogravimetric analysis. In addition, AFM and DLS analysis showed minimal change in the geometry and individualized character of CNCs after surface modification. X-ray diffraction analysis confirmed that the modification happened only at the CNC surface, while the bulk crystalline core remained unmodified. Modified cellulose/CNCs showed hydrophilic or hydrophobic properties depending on the grafted functionality, which resulted in stable colloidal suspensions of CNCs in polar and nonpolar organic solvents. Furthermore, the reactive nature of propargyl-modified cellulose was demonstrated by the successful grafting of an azido-fluorescein dye via copper-catalyzed Huisgen 1,3-dipolar cycloaddition. The triazinyl chemistry thus presents a versatile route for tuning the interfacial properties of nanocellulose, with the possibility of postmodification for applications that require the conjugation of molecules onto cellulose through bio-orthogonal chemistries.

Nanocomposites Comprising Cellulose and Nanomagnetite as Heterogeneous Catalysts for the Synthesis of Biodiesel from Oleic Acid

“…However, the larger the number of OH functional groups, the greater the number of inter-or intramolecular hydrogen bonds, making cellulose less attractive as a catalyst-supporting substance. This can be avoided by modifying the cellulose surface so that the number of active sites will increase and efficiency will be higher (Habibi, 2014;Fatona et al, 2018). Modification of the cellulose surface functionalization can be made by acetylation (Sun et al, 2016) or phosphorylation (Wanrosli et al, 2013), among other processes.…”

Cellulose Nanocrystals as a Sustainable Raw Material: Cytotoxicity and Applications on Healthcare Technology

“…Another advantage of this biomaterial is the capacity of CNCs to be easily modified chemically. Surface functionalization of CNCs aims to improve surface properties and has been intensively investigated due to the reactive surface of —OH side groups that facilitate grafting chemicals species, for example, 3‐aminopropyltriethoxysilane, to achieve enhanced thermal stability, triazinyl derivatives, resulting in stable colloidal suspensions of CNCs in polar and non‐polar organic solvents, azetidinium salts, to improve the rheological properties of CNCs, polylactide, to improve barrier properties, or genetically engineered peptides (elastin like‐polypeptides) with temperature responsiveness to produce multifunctional biopolymers . It is worth noting the chemical alteration made by Hu et al, which have proposed and environmentally friendly procedure for the surface modification of CNC with tannic acid (TA), a plant polyphenol, acting as an intermediary for the Michael‐type addition covalent of decylamine (DA), an hydrophobe group.…”

Fabrication of hydrophobic cellulose nanocrystals

“…Most of these drawbacks and disadvantages can be resolved by chemical functionalization, since they are related to the chemical nature of the CNCs’ surface. Many chemical modifications by either covalent, or non‐covalent, approaches were developed to allow CNCs to generate functional nanocrystalline cellulose particles. This was done with the purpose of avoiding the aggregation of CNCs and improving their dispersion and compatibility with a nonpolar polymer matrix.…”