Non-covalent surface modification of cellulose nanocrystals by polyethyleneimine

Cellulose nanocrystals (CNCs) are bio-derived, natively hydrophilic nanomaterials that disperse well in water according to their surface chemistry upon extraction. However, to be suspended in non-polar, hydrophobic media such as most polymers [1], the CNCs are chemically modified by reactions that are environmentally unfriendly and not cost-effective for the industry. The present work reports the preliminary findings of the non-covalent surface modification of CNCs using polyethyleneimine (PEI), a common additive used in the paper industry [2], through a low-cost process and without any use of organic solvents. The successful surface modification was confirmed through different techniques, including Fourier transform infrared (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Dynamic Light Scattering (DLS) and Zeta Potential (ζ-potential) measurements. The CNC agglomerates formed in aqueous suspensions as a result of the modification showed improved dispersion in toluene and were found to precipitate in deionized water. The turbidity measurements of the water suspensions of pristine and modified CNCs (mCNCs) were performed using UV-Visible (UV-Vis) transmission spectroscopy.