Preparation and properties of biodegradable starch-layered double hydroxide nanocomposites

Well-dispersed starch-layered double hydroxide (LDH) nanocomposites were prepared by a newly developed approach of directly synthesizing the LDH in the starch dispersion. The approach involved a fast LDH nuclei precipitation followed by a hydrothermal treatment that simultaneously leached starches from the granules and aged the LDH nuclei. X-ray diffraction and transmission electron microscopy analyses showed that the LDH crystallites homogeneously dispersed in the acid-modified corn starch (AMS) matrix, whereas they tended to aggregate in the native normal corn starch (NCS) matrix. The LDH did not significantly influence the crystalline structure of starch molecules in the nanocomposites. The addition of LDH resulted in a pronounced phase separation in NCS, but not in AMS. With 10.47 wt.% of LDH, the AMS–LDH nanocomposites displayed unchanged transparency and moisture sensitivity, and an increase in modulus by as much as 37%. Our study revealed that lower-viscous starches produced by a proper acid modification can facilitate the dispersion of LDH and improve the modulus of nanocomposites.