Preparation of cellulose nanofibers from Miscanthus x. Giganteus by ammonium persulfate oxidation

Carboxylic acid functionalized cellulose nanofibers (MxG-CNFA-CO2H) were successfully isolated from a sustainable grass hybrid Miscanthus x. Giganteus by a new two-step chemical oxidation, that involves bleach treatment and ammonium persulfate oxidation, followed by ultrasonication. The resulting MxG-CNFA-CO(2)Hs have ca. 1200 mmol/kg carboxylic acid surface groups, an aspect ratio of 230 (height of ca. 3.8 +/- 0.8 nm and length of ca. 880 +/- 300 nm) and 70% crystallinity. Interestingly, these MxG-CNFA-CO(2)Hs exhibit better thermal stability (as measured by thermal gravimetric analysis) and better dispersibility in DMF than corresponding cellulose nanocrystals (CNC) obtained from same biosource (MxG-CNC-CO(2)Hs) via acid hydrolysis. Poly(vinyl acetate): MxG-CNFA-CO2H composites show an increase in storage modulus (above T-g) with increasing filler content. Importantly, the mechanical properties of the poly(vinyl acetate):nanocellulose composites showed that the MxG-CNFA-CO(2)Hs exhibit significantly better reinforcement than the MxG-CNC-CO2H at the same weight percent filler content.