Hyperfine interaction in Zn–Al layered double hydroxides intercalated with conducting polymers

Organic–inorganic hybrid materials based on the assembly between inorganic 2D host structure and polymer have received considerable attention in the last few years. This emerging class of materials presents several applications according to their structural and functional properties. Particularly, among others, layered double hydroxides (LDHs) provide the opportunity of preparing new organically modified 2D nanocomposites.Pyrrole carboxylic acid derivatives, namely 4-(1H-pyrrol-1-yl)benzoate, 3-(pyrrol-1-yl)-propanoate, 7-(pyrrol-1-yl)-heptanoate, and aniline carboxylic acid derivative, namely 3-aminobenzoic acid, have been intercalated in LDHs of intralamellar composition Zn2Al(OH)6. The LDHs were synthesized by the co-precipitation method at constant pH followed by hydrothermal treatment for 72 h. The materials were characterized by powder X-ray diffraction patterns (PXRD), transmission electron microscopy (TEM) thermogravimetric analysis (TGA), and electron spin resonance (ESR). The basal spacing found by the PXRD technique gives evidence of the formation of bilayers of the intercalated anions. ESR spectra present a typical signal with a superhyperfine structure with 6+1 lines (g  =2.005±0.0004), which is assigned to the interaction between a carboxylate radical from the guest molecules and a nearby aluminium nucleus (I=52) from the host structure. Additionally, the ESR data suggest that the monomers are connected to each other in limited number after thermal treatment.