X-ray diffraction and dynamic mechanical analyses of alpha-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibers

Electrospinning is a facile method for preparing nanocomposite materials in fiber form. Nanomaterials that have been incorporated within such fibers are usually inorganic in nature. Recently, nanocomposite nanofibers based on poly(vinyl alcohol) (PVA) as the matrix and nanocrystals of alpha-chitin (i.e. chitin whiskers; ca 31 nm in width and ca 549 nm in length on average) as the nanofiller have been successfully prepared. In the study reported here, the fibers were further investigated using X-ray diffraction (XRD) and dynamic mechanical analyses in comparison with the corresponding solvent-cast films. The average diameters of the PVA/chitin whiskers fibers ranged between 175 and 218 nm. Careful analysis of the wide-angle XRD patterns of the fiber mats and the films showed that PVA was partially crystalline, and the incorporation of the whiskers within the fibers was confirmed by peaks characteristic to alpha-chitin crystals. Dynamic mechanical analysis showed that the fiber mats were weaker than the films and that the relaxation temperatures associated with the glass transition (T-g) of the fiber mats were greater than those of the films. The addition and increasing the amount of the whiskers caused the crystallinity of PVA within the nanocomposite materials to decrease and T-g to increase. The present study shows that the geometry of nanocomposite materials plays a major role in determining their properties. (C) 2009 Society of Chemical Industry