Modification of Mg/Al-layered double hydroxide with l-aspartic acid containing dicarboxylic acid and its application in the enhancement of the thermal stability of chiral poly(amide-imide)

Abstract

In this study, Mg/Al-layered double hydroxide (LDH) was intercalated with diacid containing L-aspartic acid in one step using an ultrasonic method under green conditions. Organic diacid was used as a modifier to enhance their compatibility and led to better dispersion of LDH nanoclay in the polymer matrix. An effective intercalation of the examined diacid in LDH was confirmed by an increase in the basal spacing of the obtained products in comparison with Mg/Al-CO₃²⁻ LDH precursors using X-ray diffraction. An optically active poly(amide-imide) (PAI) was synthesized via polycondensation of N,N-(pyromellitoyl)-bis-phenylalanine diacid with 4,4-diaminodiphenylsulfone in molten tetrabutylammonium bromide. The modified LDH (M-LDH) was used as a filler in the PAI matrix and PAI/M-LDH nanocomposites containing 2, 4 and 8% of M-LDH were fabricated. Thermogravimetric analysis showed an improvement in the thermal stability and morphology investigations by field emission scanning electron microscopy and transmission electron microscopy displayed that M-LDH is dispersed in the PAI matrix.