Comparing Soft Semicrystalline Polymer Nanocomposites Reinforced with Cellulose Nanocrystals and Fumed Silica

This work compares solvent-cast poly­(ethylene oxide) (PEO) nanocomposites reinforced with cellulose nanocrystals (CNCs) and fumed silica. Mechanical properties and crystallization behavior were investigated over a range of polymer molecular weights (10 000–100 000 g/mol) and particle loadings (1–10 wt %). Polymer adsorption to CNCs and fumed silica was found to alter PEO undercooling and inhibit crystal nucleation. Atomic force microscopy revealed PEO adsorbs to CNCs in a shish-kebab morphology that is readily incorporated into the crystalline domains of the polymer. Tensile testing and nanoindentation showed that Young’s modulus increased by more than 60% for CNC reinforced nanocomposites, and that the Halpin–Kardos model could effectively describe the mechanical properties. Fumed silica reinforced nanocomposites were fit to the Guth–Gold micromechanical model using effective particle volume fractions. Although only solvent-cast nanocomposites were investigated, this work provides new insight into the interactions that control dispersion, crystallization, and mechanical reinforcement.