Electrochemically Modulated Permeability of Poly(aniline) and Composite Poly(aniline)−Poly(styrenesulfonate) Membranes

Abstract

The influence of oxidation state on the permeability of several probe molecules through conducting polymer membranes comprising composites of poly(aniline) and poly(styrenesulfonate) was examined in aqueous solution. Pure poly(aniline) membranes displayed a characteristic increase in permeability between reduced and half-oxidized states for neutrally charged phenol and negatively charged 4-hydroxybenzenesulfonate. In contrast, positively charged pyridine experienced decreased permeability through the membrane when poly(aniline) was switched from the reduced to the half-oxidized state. This behavior can be explained by a combination of oxidation-induced film swelling and the anion-exchange character of the positively charged membrane. The membrane composition was modified to include a fixed negative charge by the addition of poly(styrenesulfonate) during synthesis. The incorporation of this negatively charged component introduced cation-exchange character to the film and substantially reduced membrane permeability to 4-hydroxybenzenesulfonate in both oxidation states. In addition, increasing the fraction of poly(styrenesulfonate) in the membrane served to decrease film permeability for all species because of a densification of the membrane. This work demonstrates how both film composition and oxidation state can be used to tune the permeability of conducting polymer membranes.

Self‐doped sulfonated polyaniline ultrafiltration membranes with enhanced chlorine resistance and antifouling properties

“…Free volume shrinkage may take place while exposing the membrane to reducing agents, which lead to reduction or expulsion of cations. In contrast, free volume swelling occurs by the addition of cations to a fully reduced polymer 81 . This explains the tuneable properties, which affect the solution transport and the slight subsequent change in membrane morphology.…”

Linking the Tuneability and Defouling of Electrically Conductive Polyaniline/Exfoliated Graphite Composite Membranes

“…EG possesses highly mobile electrons, and polarons were formed to move along the polymer backbone by applying an external potential, causing the movement of counterions in the polymer chains. This resulted in the reorganization of the polymer structure, permitting a more open membrane structure accompanied by the expansion of membrane [ 45 ]. The created voids or free volume allowed more water to pass through the membrane [ 46 ].…”

Study of Polyaniline/Poly(Sodium 4-Styrenesulfonate) Composite Deposits Using an Electrochemical Quartz Crystal Microbalance for the Modification of a Commercial Anion Exchange Membrane

“…However, it is not possible to find research with similar results related to this property of PAni/PSS composites. Only Pile et al [36] analyzed the effect of oxidation state on the permeability of several probe molecules through conducting polymer membranes comprised of PAni composites in a PAni/PSS aqueous solution. For example, they found that the permeability of the reduced state of composite is very similar to that observed for the pure PAni film compared to the oxidized state.…”