A two-step polyaniline (PANI) loading procedure has been developed to produce polyelectrolyte complex composite membranes (CPECs) to be used as supercapacitor electrodes. In the first step, CPECs were prepared by co-precipitation of poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) mixed with various amounts of PANI as a filler. CPECs were formed by compression molding into 100 micron membranes using NaCl as a plasticizer and characterized for their electrochemical properties. In the second step, the highest capacitance CPEC membranes with 60% PANI loading were further modified and doped by crossflow polymerization of aniline through the composite membranes. By using a two-compartment crossflow reactor containing aniline and ammonium persulfate on each side, the PANI content of the composite membrane was further increased. Cyclic voltammetry showed a doubling in the capacitance of the membranes after the crossflow polymerization. The resulting electrodes were flexible with high capacitance and could be used to improve pseudocapacitor performance.

Polyelectrolyte complex (PEC) membranes prepared from poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) were modified by crossflow polymerization of aniline (ANI). The PEC membranes were used as separators in a two-compartment setup where ANI monomer and ammonium persulfate (APS) oxidant diffused through the membranes to form polyaniline (PANI). APS and ANI having different distributions throughout the membranes, the reaction led to the asymmetric polymerization of PANI on one face of each PEC membrane thus producing Janus membranes. Due to the excess PANI content, the membrane displayed distinct asymmetric electrical conductivities on each face. Interestingly, very different ANI polymerizations were obtained when nonstoichiometric PEC membranes having different molar ratio of cationic and anionic polyelectrolytes (P + :P − represents PDADMAC:PSS) were used and transport of APS was fastest through the 2:1 PEC when compared to the 1:2 PEC. In all experiments, the polymerization was most intense on the ANI side of the membranes. Also, the influence of NaCl both during PEC fabrication and during polymerization was studied and found to have some effect on the solute permeability. Results showed that a higher content of PANI was formed on PEC membranes having excess P + and with no NaCl added during PEC fabrication. Although X-ray diffraction confirmed the presence of PANI on both sides of each membrane, scanning electron microscopy images demonstrated that both sides of each membrane had different PANI content deposited. Electrical conductivity measurements using a four-point probe setup also showed that the PEC-PANI exhibits asymmetric electrical property on different sides.

The direct polymerization of a polymer in a polyelectrolyte complex membrane is a quick and simple method to enhance the properties and add functionality to a pre‐formed membrane. Here, polyelectrolyte complex membrane (PECs) of poly (diallyl dimethyl ammonium chloride) (PDADMAC) [P+] and poly (styrene sulfonate) [P−] were modified by the in‐situ polymerization of aniline monomer into polyaniline (PANI). The initial PECs were prepared by the co‐precipitation of polyelectrolytes with various [P+]: [P−] molar ratio and were formed into 100 micron thin membranes by compression molding. The in‐situ polymerization of PANI was achieved by sequential dipping of the PECs in ammonium peroxydisulfate solution to load the oxidant and in the aniline monomer solution to initiate the polymerization. Both the polyelectrolyte stoichiometry and the NaCl concentration used during the formation of the complex were found to have a profound effect on the polymerization reaction. UV–visible spectroscopy, X‐ray diffraction, and infrared spectroscopy were used to characterize the changes in color of the PANI membranes and to confirm the synthesis of PANI. Scanning electron microscopy revealed the presence of a dense coating of PANI at the surface of the PEC.