Intercalation of poly(ethylene oxide) derivatives into layered double hydroxides

Mono- and bi-functional guest molecules, poly(ethylene glycol)-n-alkyl-3-sulfopropyl diether (PEG-AS) and poly(ethylene glycol)dicarboxylic acid (PEG-DC), containing hydrophilic polyoxyethylene (PEO) chains of different ethylene oxide units (EOUs) are incorporated between the layers of Cu2Cr(OH)(6)Cl.nH(2)O hydrotalcite-type materials. The intercalation compounds are characterized by chemical analysis, adsorption measurements, XRD, SEM, FTIR and C-13 CPMAS spectroscopy. It is found that the polyoxyethylene chain of PEG-DC distorts its helical symmetry when it is intercalated in the LDH galleries. The basal spacing of PEG-AS nanocomposites is independent of the number, n, of EOUs in the polymer chain. In addition to changes in the IR bands, C-13 CP-MAS spectra are modified with new resonance peaks at more deshielded values. These facts suggest a strong interaction of polyether chains with the LDH inner-surface, with the hydrophobic alkyl tail dangling into the interlamellar space. It is shown that the terminal functionalities dictate the arrangement of the PEO chains. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).