Modified Cellulose Nanocrystals Enabled Antimicrobial Polymeric Films

Abstract

AbstractThis study presents an antimicrobial polymeric material comprising cellulose nanocrystals (CNCs) grafted with an antimicrobial oligomer, polyhexamethylene guanidine hydrochloride (PHGH). A one‐pot reaction is implemented to graft PHGH onto CNCs, creating a non‐leaching and nano‐sized antimicrobial additive (mCNC). The mCNC is subsequently incorporated into a model polymer, polylactic acid (PLA), with concentrations of 2.5 to 10 wt.% and tested for its antimicrobial activity during dynamic and static contact with Escherichia coli and Bacillus subtilis bacteria. The grafting of PHGH onto CNC is confirmed with Fourier transform infrared spectroscopy (FTIR), X‐ray spectroscopy (XPS) and elemental analysis. The effect of mCNC incorporation at various loading levels on the morphology and physicomechanical properties of PLA is investigated with polarized optical microscope (POM), scanning electron microscope (SEM), dynamic mechanical analysis (DMA), tensile testing, and differential scanning calorimetry (DSC). In terms of the antimicrobial action, the films exhibited potent efficacy against Gram‐positive bacteria (B. subtilis), with growth inhibition of 3.97 to 4.66‐log reduction. However, 10 wt.% of mCNC loading is needed to achieve a significant bacterial inhibition (>6.24‐log) of the Gram‐negative bacteria (E. coli). Overall, the incorporation of PHGH grafted CNCs in polymers provided a non‐leaching antimicrobial film that has potential application in food packaging.