Influence of morphological diversity of cellulose nanocrystals and nanospheres on nanocomposites with chitosan

In this work, we employed two distinct processes to produce rod-like cellulose nanocrystals (CNCs) and cellulose nanospheres (CNSs) from Juncus-cellulose using acid hydrolysis and TEMPO oxidation, followed by ultrasonication. The structural, thermal, and optical properties of the resulting nanocomposites were thoroughly evaluated. At the same time, the mechanical properties were experimentally measured and compared with theoretical predictions using three mechanical models, with correlations drawn to the nanocomposite microstructures. Our findings highlight distinct differences between short, rigid CNCs and spherical CNSs in their reinforcing mechanisms, offering practical insights for polymer nanocomposite development incorporating cellulose nanomaterials. Optimal performance was achieved with 5% of nanofillers loading, improving the thermal, optical, and mechanical properties, showing a significant increment in Young's modulus (YM) and in tensile strength (TS) by 137 and 22%, respectively, for CNSs and a slight increment for CNCs of 53.4 and 1.46%, respectively, over neat chitosan films (~ 4.77 × 10³ ± 0.16 MPa and 47.14 ± 7.86 MPa). The study reveals that the morphology of nanocellulose plays a crucial role in determining the mechanical properties of chitosan-based nanocomposites. These findings offer practical insights into the selection and optimization of nanocelluloses for enhancing polymer nanocomposites, with promising applications in developing materials with superior mechanical, thermal, and optical performance.