Intercalation of layered double hydroxides by poly(oxyalkylene)-amidocarboxylates: tailoring layered basal spacing

Mg-Al layered double hydroxides (LDHs) were intercalated with various molecular-weight poly(oxypropylene)-bis-amidoacid salts (POP-acid), synthesized from polyoxyalkylene-diamines and maleic anhydride. The intercalation involves an ionic exchange reaction of LDHs at 120 °C and under N₂ atmosphere in an autoclave to afford a series of organoclays with a maximal basal spacing of 92 Å, revealed by X-ray diffraction and transmission electron microscopy analyses. The unusually wide interlayer spacing was ascribed to the self-alignment of the hydrophobic POP backbone in the layer confinement. In contrast, the intercalation of poly(oxyethylene)-bis-amidoacids (POE-acid) afforded a low basal spacing (7.8 Å) due to their oxyethylene-backbone interaction with the layered surface. The resultant POP- and POE-acid intercalated LDHs also exhibited different dispersing properties in toluene or water. Particularly, the organically-modified and space-enlarged hybrids with a proper amount of the embedded POPs possessed an amphiphilic property of lowering the toluene/water interfacial tension.