Mg–Al Layered Double Hydroxides Intercalated with Polyetheramidoacids and Exhibiting a pH-Responsive Releasing Property

Mg–Al layered double hydroxides (LDH) are prepared by coprecipitation of Mg(NO3)2 and Al(NO3)3 and subsequently incorporated with poly(oxypropylene)-bis-amidocarboxylic acid (POP). When characterized by X-ray diffraction, the interlayer spacing of the synthesized POP/LDH hybrids were found to be spatially expanded, with basal spacing ranging from 33–94 A, proportionately correlated to the POP molecular weight of 400–4000 g/mol. With increasing POP molecular weight incorporation, a critical d-spacing is reached when the POP/LDH hybrids become hydrophobic. The organo-LDH units possessed an amphiphilic property and ability of dispersing in water, ethanol, and toluene. Furthermore, the hybrid was actually stable under basic conditions but structurally disintegrating at pH 2 through the release of POP organics into aqueous solution. The understanding of the mechanism involving basal spacing shrinkage and structure disintegration allows the future development of utilizing the POP-modified clay as pH-sensitive a...