Enhancement of the Thermo- and Photostability of an Anionic Dye by Intercalation in a Zinc−Aluminum Layered Double Hydroxide Host

Intercalation of 2-hydroxy-5-(4-sulfophenyl azo)-benzoate disodium salt into ZnAl−NO 3 layered double hydroxide was carried out in an effort to improve its thermostability and photostability. After intercalation, the powder X-ray diffraction pattern showed that the interlayer distance of the LDH increased from 0.90 to 1.54 nm, suggesting that the HSAB anions are arranged in the interlayer galleries of ZnAl−HSAB−LDH as a tilted monolayer of dianions. Infrared spectra and TG-DTA curves revealed the presence of a complex system of supramolecular host−guest interactions between LDH layers and HSAB anions. The thermostability of HSAB and ZnAl−HSAB−LDH was investigated by TG-DTA and UV−vis spectroscopy; it was found that ZnAl−HSAB−LDH was more stable than HSAB at high temperatures. Photostability tests showed that ZnAl−HSAB−LDH exhibited higher stability to UV radiation than either HSAB or a physical mixture of HSAB and ZnAl−NO 3 −LDH. In their composites with polyethylene, it was also found that ZnAl−HSAB−LDH possesses better thermostability and photostability than HSAB.