Intercalation of γ-PGA in Mg/Al layered double hydroxides: An in situ WAXD and FTIR investigation

gamma-Poly(glutamic acid) (gamma-PGA), an anionic, hydrophilic and biodegradable polymer, was selected to modify the magnesium/aluminum (Mg/Al) layered double hydroxide (LDH) using the anion exchange method. The wide-angle X-ray diffraction (WAXD) and Fourier transform infrared (FTIR) methods were used to identify the incorporation behavior of gamma-PGA within the inorganic nanolayers of LDH. The thermal decompositions of original and gamma-PGA-modified LDHs, including dehydration and dehydroxylation together with decomposition of intercalated anions, were investigated by thermogravimetric analyses (TGA). In addition, the effect of temperature on the real-time structural and dehydration behavior of gamma-PGA intercalated LDH was investigated in detail by means of in situ WAXD and in situ FTIR. The results clearly indicated that the dehydration of organically-modified LDH has resulted in the contraction of the interlayer spacing from 15.0 angstrom to 11.5 angstrom as temperature increases from 30 to 130 degrees C. This behavior might be ascribable to the elimination of interlayer constitution water, which has resulted in the destruction of hydrogen bonding among of hydroxide sheets, intercalated anions and water molecules. However, the layered structure of the dehydrated LDH remains unchanged up to 250 degrees C. (c) 2010 Elsevier B.V. All rights reserved.