In situ polymerization of interleaved monomers: a comparative study between hydrotalcite and hydrocalumite host structures☆☆Keynote Lecture. Original Research Article

Vinyl benzene sulfonate (styrene sulfonate, VBS) and polystyrene sulfonate (PSS) were incorporated into Layered Double Hydroxides (LDH) by templating reaction. The two host structures investigated are Zn2Al(OH)6Cl. nH2O of hydrotalcite-type and Ca2Al(OH)6Cl. nH2O of hydrocalumite-type. The electrostatic binding between sulfonate groups of VBS and the inner-surface of LDH host structure evaluated by 13C CP-MAS NMR spectroscopy causes some shifts in the resonance lines. In situ polymerization of VBS molecules between LDH sheets is reached after soft heat treatment. Its completion requires a good matching between the layer charge density and the projected surface area of the guest molecule achieved by a ratio M2+ to M3+ of 2. For the pristine material, the change from Oh to Td aluminum site appears to be a collective process for the hydrocalumite, whereas it is more progressive for the hydrotalcite-type material. For the corresponding organoceramics, the site conversion before the breakdown of the lamellar structure is substantially reduced, and especially for PSS/LDH nanocomposite obtained by in situ polymerization. CaAl–VBS intercalate crystallizes in C2/c space group inducing a bilayer arrangement of VBS anions in the interlamellar space. Furthermore, distances between anionic sites allow an in situ zig-zag polymerization of syndiotactic type along the a axis. For hydrotalcite, the short Al3+–Al3+ distance at a√3 prevents also the formation of PSS other than syndiotactic. The thermal stability of the nanocomposites depends on the host structure but also on the synthesis pathway.