Preparation of hydrocalumite-based nanocomposites using polycarboxylate comb polymers possessing high grafting density as interlayer spacers

Fabrication of nanocomposites derived from layered double hydroxides is described. Synthesis was accomplished by rehydration of tricalcium aluminate (Ca3Al2O6, abbreviation C3A) in the presence of “comb like” polycarboxylate copolymers (PCs). The PCs possess low anionic charge density and high grafting density. Their side chains were made up of between 4.5 and 111 ethylene oxide units (EOUs). It was found that the length of the side chain in PC determines whether intercalation occurs or not. Polymers possessing short to medium size side chains intercalate well whereas PCs with long side chains interact with C3A by surface adsorption only rather than chemical absorption. XRD, IR spectra, thermogravimetry (TG), elemental analysis and TEM images confirm that for polymers possessing side chains made of 4.5–45 EOUs, nanocomposites are formed with layered structure whereby the PCs are intercalated in between the inorganic [Ca2Al(OH)6]+ host layers. Interlayer distance depends on the length of the side chains. The organic parts of the nanocomposites vary between 39 mass% and 62 mass%, resp. In contrast, PCs possessing long side chains (111 EOUs) do not show any significant intercalation. Their high grafting density coupled with large steric size of the side chain does not allow compression of the graft chains which is necessary for the molecule to fit in between the inorganic main layers. The results indicate that synthesis of inorganic–organic hybrid materials showing a controlled variation of the interlayer distance is possible by using the PCs studied here that possess high grafting density.