Hydrocalumite and Its Polymer Derivatives. 2. Polymer Incorporation versus in Situ Polymerization of Styrene-4-sulfonate

Hydrocalumite, Ca2Al(OH)6(anion)·nH2O, belongs to the layered double-hydroxide family, with the particularity for both intralayered cations and interlayered anions and water molecules to be well-ordered. The monomer vinyl benzene sulfonate (VBS) and the syndiotactic polymer poly(styrene sulfonate) (PSS) were readily incorporated into its lamellar structure via a coprecipitation method. In situ thermal polymerization of the monomer VBS is simultaneously supported by the disappearance of the vinyl bond and the formation of −CH, −CH2 bonds. These facts are evidenced by the experiments performed by 13C solid-state NMR and FTIR spectroscopies. CaAl−VBS intercalate crystallizes in the C2/c space group, inducing a bilayer arrangement of VBS anions in the interlamellar space. Besides, distances between anionic sites allow an in situ zigzag polymerization of syndiotactic type along the a axis. Additionally, the contraction of the lamellar structure is found to be reversible up to 200 °C; the adjacent monomers then start to attach to each other via polymerization. The thermal stability is found to be highly dependent on the synthesis pathway. The decomposition is delayed up to 450 °C for the sample prepared via in situ polymerization while as-prepared PSS intercalate decomposes at lower temperature. Under a nitrogen atmosphere, CaS is formed at 700 °C.