Novel all-cellulose composite displaying aligned cellulose nanofibers reinforced with cellulose nanocrystals

Abstract

Aligned cellulose nanocrystals/cellulose coelectrospun nanofibers were successfully prepared by using a home-built coelectrospinning and collection system. Cellulose I was dissolved in N-methyl morpholine oxide at 120°C and diluted with dimethyl sulfoxide, which was used in the external concentric capillary needle as the sheath (shell) solution. A cellulose nanocrystal suspension obtained by sulfuric acid hydrolysis of cotton fibers was used as the core liquid in the internal concentric capillary needle after transferring from water to dimethyl sulfoxide. The resultant coelectrospun nanocomposite films were collected onto a rotating wire drum and were characterized by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy, thermogravimetric analysis, and tensile measurements. The FE-SEM image showed that the cellulose nanocrystals did not appear to cluster in the film formed. Although the crystallinity index of nanocomposite fibers was lower than the unreinforced cellulose electrospun fibers, the cellulose type II reinforced with cellulose nanocrystals had a much higher tensile stress (about 140 MPa), almost twofold that of pure cellulose. This latter result indicated that the alignment and adhesion of amorphous cellulose nanofibers played a crucial role on the mechanical properties of electrospun cellulosic fiber mats.