Synthesis and characterization of a polystyrene sulfonate layered double hydroxide nanocomposite. In-situpolymerizationvs. polymer incorporation

Abstract

Vinyl benzene sulfonate (styrene sulfonate — VBS) and polystyrene sulfonate (PSS) are incorporated into layered double hydroxides (LDH) of nominal composition Zn_nAl(OH)_2(1+n)Cl·nH₂O by exchange and templating reaction, respectively. PSS adsorption leads to a delamination process of the LDH 2D-host structure. A hydrothermal treatment improves greatly the crystallinity of the PSS–LDH nanocomposite. The interactions between VBS and the host structure are evaluated by ¹³C CP-MAS solid state NMR spectroscopy. The electrostatic binding between the sulfonate group and the inner-surface of the LDH host structure causes some shifts in the resonance lines, although the shifts are independent of the LDH layer charge density. 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 as exemplified by a Zn to Al ratio of 2. In comparison to the pristine material, the change from Oh to Td aluminium site is substantially reduced for PSS–LDH nanocomposite and absent for the material prepared after the polymerization reaction.