Bioploymer/Layered Double Hydroxide Nanocomposites: Preparation, Structure And Properties

In this article, the exfoliated layered double hydroxide (LDH)/bioploymer nanocomposites have been prepared successfully in a one-stage process by the solution intercalation technique or reconstruction method and in-situ preparation, respectively. The above-mentioned biopolymers included carboxymethyl cellulose (CMC), carboxymethyl chitosan (CMCS), carboxymethyl starch (CMS) and polyaspartate-carboxymethyl chitosan. The structures and morphologies of the nanocomposited were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). And influences of different amounts of layered double hydroxides on the mechanical properties, thermal stability or controlled drug release and electrorheological effects of nanocomposites were investigated.The XRD results showed that the layered double hydroxides were almost exfoliated and incorporated within the bioploymer matrixes at the nanometer level. The mechanical properties and thermal stability of the nanocomposites are enhanced in varying degrees by adding layered double hydroxide. The tensile strength and elastic modulus of the CMC composite with a 3% of Mg-Al-LDH loading gave a dramatic improvement of 120 and 228%, respectively, while its elongation at break decreased. The decomposition temperature was a slightly higher than that of CMC from the thermogravimetric analysis (TGA) result. The hardness and modulus of the CMCS were increased by about 41% and 30%, respectively, with the addition of 5 wt% Mg-Al-LDH. When the content of Mg-Fe-LDH was 50%, the shear stress of the CMS composite electrorheological fluid reached to the maximum. The maximum decomposition temperature of the CMS composite with the addition 50% Mg-Fe-LDH increased by 93℃compared with pure CMS. To determine the release profile of guanine from the nanocomposite films, we conducted drug-release studies with UV method. The percentage cumulative drug release increased with the amount of guanine in the polyaspartic acid-carboxymethyl chitosan/LDH nanocomposites.