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

ELIANA MAZA; JIMENA S. TUNINETTI; NIKOLAOS POLITAKOS; WOLFGANG KNOLL; SERGIO MOYA; OMAR AZZARONI

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2015 vol. 17 p. 29935 - 29948

1463-9076

The layer-by-layer construction of interfacialarchitectures displaying stimuli-responsive control of masstransport is attracting increasing interest inmaterials science. In this work, we describe the creation ofinterfacial architectures displaying pH-dependentionic transport properties which until now have not beenobserved in polyelectrolyte multilayers. We describe anovel approach to create pH-controlled ion-rectifyingsystems employing polyelectrolyte multilayersassembled from a copolymer containing both weakly andstrongly charged pendant groups,poly(4-styrenesulfonic acid-co-maleic acid) (PSS-MA), alternately depositedwith poly(diallyldimethylammonium chloride) (PDADMAC).The conceptual framework is based on the verycontrasting and differential interactions of PSS andMA units with PDADMAC. In our setting, sulfonate groupsplay a structural role by conferring stability to themultilayer due to the strong electrostatic interactionswith the polycations, while the weakly interacting MAgroups remain ??silent?? within the film and then actas on-demand pH-responsive units. When thesemultilayers are combined with a strong cationiccapping layer that repels the passage of cationicprobes, a pH-gateable rectified transport of anions isobserved. Concomitantly, we also observed that thesefunctional properties are significantly affectedwhen multilayers are subjected to extensive pH cyclingas a consequence of irreversible morphologicalchanges taking place in the film. We envision that thesynergy derived from combining weak and stronginteractions within the same multilayer will play akey role in the construction of new interfacialarchitectures displaying tailorable ion transportproperties.