Selective removal of hybrid di-block polyelectrolyte multilayers by means of quaternary ammonium surfactants

The stability of polyelectrolyte multilayers (PEMs), fabricated by the layer-by-layer (LBL) assembly, upon treatment with the tetradecyl trimethyl ammonium bromide (TTAB) surfactant, was studied for multilayers composed of poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) or poly(diallyldimethylammonium chloride) (PDADMAC) and PSS, and for hybrid PEMs formed by two blocks: a PEM of PAH/PSS with a PDADMAC/PSS PEM on top. The assembly of the PEMs was followed by means of the quartz crystal microbalance with dissipation technique (QCM-D). Also, QCM-D either alone or in combination with spectroscopic ellipsometry was used to study the interaction of the PEMs with TTAB at concentrations below and over the critical micellar concentration (CMC). While sole PDADMAC/PSS multilayers were completely removed with TTAB at concentrations over the CMC, PAH/PSS multilayers remained stable and adsorbed the surfactant. Nevertheless, for the combination of PAH/PSS with PDADMAC/PSS, the layers of PDADMAC/PSS on top were only partially removed. Increasing the number of PAH/PSS layers decreased the amount of PDADMAC/PSS that was removed.