pH-responsive ion transport in polyelectrolyte multilayers of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA) bearing strong- and weak anionic groups

Abstract

The layer-by-layer construction of interfacial architectures displaying stimuli-responsive control of mass transport is attracting increasing interest in materials science. In this work, we describe the creation of interfacial architectures displaying pH-dependent ionic transport properties which until now have not been observed in polyelectrolyte multilayers. We describe a novel approach to create pH-controlled ion-rectifying systems employing polyelectrolyte multilayers assembled from a copolymer containing both weakly and strongly charged pendant groups, poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA), alternately deposited with poly(diallyldimethylammonium chloride) (PDADMAC). The conceptual framework is based on the very contrasting and differential interactions of PSS and MA units with PDADMAC. In our setting, sulfonate groups play a structural role by conferring stability to the multilayer due to the strong electrostatic interactions with the polycations, while the weakly interacting MA groups remain "silent" within the film and then act as on-demand pH-responsive units. When these multilayers are combined with a strong cationic capping layer that repels the passage of cationic probes, a pH-gateable rectified transport of anions is observed. Concomitantly, we also observed that these functional properties are significantly affected when multilayers are subjected to extensive pH cycling as a consequence of irreversible morphological changes taking place in the film. We envision that the synergy derived from combining weak and strong interactions within the same multilayer will play a key role in the construction of new interfacial architectures displaying tailorable ion transport properties.

Release kinetics study and anti-corrosion behaviour of a pH-responsive ionic liquid-loaded halloysite nanotube-doped epoxy coating

“…In PEM formation, the deposition of polyelectrolyte will always result in neutralization of the surface charge of the outermost layer, while the overcompensation of charge becomes the driving force for subsequent deposition of the alternating polyelectrolyte. 30,44 The zeta potential reversed to À11.39 mV aer deposition of the second PAA layer. These zeta potential values were similar to results reported by Abdullayev and his coworkers, who observed a range from +15 to 32 mV for the rst layer of PEI deposition but a slightly lower range for the PAA layer of around À15 to À30 mV.…”

“…The deposition through electrostatic attraction can be applied with a wide variety of building blocks, allowing the incorporation of a broad range of functional units. 30 PEMs have been constructed that possess distinctive properties based on their individual polyelectrolytes, 30,31 molecular weight, 32 salt concentration, 33,34 and pH. 35 It has also been reported that the ultimate properties of PEMs are highly dependent on the outermost assembled layer.…”

Assessment of Layer-By-Layer Modified Nanofiltration Membrane Stability in Phosphoric Acid

“…Besides our studies, very few publications have reported on the behavior of PE in an acidic environment. In most of these studies either weak PE were chosen, which were not stable at low pH levels, or the pH was not decreased below 3.5, as is needed to truly estimate the behavior of LbL membranes during harsh acidic applications [24][25][26], whereas strong PE such as PDAMAC and PSS are constantly charged independent of pH. Menne et al [13] also showed excellent pH stability (0-14) of PE coated on ceramic UF membranes in HCl.…”

Shannon entropy associated with electrochemically generated ion concentration gradients

“…The diffusion of oxidation products is highly affected by the structure of the electrode surface [5,6]. Polyelectrolyte modified electrodes are of high interest [7,8].…”