Enhanced dispersion and interface compatibilization of crystalline nanocellulose in polylactide by surfactant adsorption

In this study, the surface polarity of sulfated crystalline nanocellulose (CNC) was tailored using an ecologically compatible surface modification strategy. Lauric arginate, a novel biologically-derived cationic surfactant, was ionically bonded to the CNC surface sulfate groups forming a monolayer that significantly increased surface hydrophobicity. Both unmodified (P-CNC) and surfactant modified (F-CNC) were incorporated into a non-polar PLA matrix to study their reinforcing effect. The P-CNC, ascribed to its inherent hydrophilic characteristic, had limited nucleating and reinforcing effect on the PLA matrix. Large nanoparticle aggregation and interface debonding were easily discernable in P-CNC/PLA nanocomposite films. The hydrophobic F-CNC, by contrast, had a much better dispersibility and interface compatibility within the PLA matrix. The cold crystallization rate, crystallinity, storage modulus (glassy and rubbery states), glass transition temperature, and tensile strength and modulus of F-CNC/PLA nanocomposite films were remarkably enhanced with appropriate loading level of F-CNC (<5 wt%). These results demonstrate an efficient route to increase the hydrophobicity of CNC for its enhanced nanoreinforcing effect in various non-polar matrices.