Electrochemically-induced charge and mass transport in polypyrrole/poly(styrene sulfonate) molecular composites

Abstract

P o l y p y r r o l e / p o l y ( s t y u~o~~) (PP/PSS) molecular composites have been synthesized by the electrochemical polymerization of pyrrole in the presence of sodium poly(styrenesu1fonate) (PSS-Na+). Their synthesis and charge transport properties have been investigated by a combination of electrochemical and gravimetric techniques using the Electrochemical Quartz Crystal Microbalance (EQCM). Electropolymerization in water at 0.8 V vs Ag/AgCI yields a partially hydrated polymer complex with sulfonate dopant anions from PSS. Mass transport is found to be cation specific, as expected for a composite system, with the polyelectrolyte chains physically entrapped within the polymer membrane. Frequency responses of the EQCM during electrochemical switching are found to increase with increasing electrolyte cation mass as Li+ r Na+ C Cs+ C Et4N+ C Bu4N+. Chronogravimetric and chronocoulometric analyses of PP/PSS-Na+ yield apparent diffusion constants, Dm between lo4 and lo-" cm2 s-I for mobile hydrated Na+ species. Though the determinations of these values are complicated by the exact determination of the concentration of electroactive sites (Co*), it is evident that reductive transport processes are faster than oxidative transport processes during switching. IntroductionThe electrochemical preparation of electrically conductive blends and composites of polyheterocycles, with a variety of carrier polymers has led to a new class of multicomponent materials with controllable electrical, electrochemical, and mechanical properties. The ultimate properties result from the intrinsic properties of both the polyheterocycle, and the carrier polymer, along with specific interactions between the two polymers. A number of composites of polyheterocycles with matrix supporting polymers and polyelectrolytes have appeared in the literature. Early work on these systems involved the electrochemical polymerization of a heterocycle within a predepasited, solvent-swollen thermoplastic polymer matrix on an electrode surface. Several systems have been prepared in this manner, including composites of polypyrrole with poly(viny1 chloride),2 poly(viny1 al~ohol),~ polystyrene,& poly-(methyl methacrylate),% and vinylidene chloride-vinyl chloride copolymers.& This method has been improved by saturating the supporting polymer matrix with an electrolyte prior to deposition and subsequent electropolymerization.'A common problem encountered in films prepared by this method is an irregular conductivity across the thickness of the film as a result of the polymerization originating at the electrode/matrix interface, which then proceeds outward through the film as the monomer diffuses in. These problems were only partially alleviated by the electrolyte-doped host matrix.Composite films of poly(3-methylthiophene) with poly(methy1 methacrylate) and poly(viny1 chloride) have been prepared by using a simple one-step procedure involving electropolymerization onto a metallic electrode from a solution containing 3-methylthiophene, supporting electrolyte, an...

Nanostructured Coatings for Improved Charge Delivery to Neurons

“…The polyanionic dopant polystyrene sulfonate (PSS) has seen popular use due to excellent coating characteristics [182,196]. Large dopants such as PSS are typically trapped and immobilized within the bulk of the CP; in vitro electrochemical quartz crystal microbalance (EQCM) studies have verified that polyanionic dopants such as PSS (MW: 100,000) [197] remain within CP films as the CP is reduced and that the ionic flux into and out of the film in such systems consists of small cations which associate with the polyanionic species. It is important to consider the size of the dopant molecules, as smaller dopants tend to leach out of the CP matrix over time, leading to loss of conductivity.…”

Electrochemical Characterisation of Polypyrrole Doped with p‐Sulfonatocalix[4]arene

“…Therefore, as observed by Kim et al [13] for a PPy-C6S system, reduction of the PPy-C4S film is accompanied by an influx of cations. The sharper appearance of the reduction wave for these films has been attributed to the high mobility of the cations and to the ionic concentration gradient between the bulk electrolyte and the film [33]. During the reduction process cations are able to diffuse into the cation starved film to compensate the charge of the immobilised anions.…”

Técnicas in situ de baixo custo em eletroquímica: a microbalança a cristal de quartzo

“…A troca de solvente pode ser associada com a camada de solvatação dos íons ou com a diferença de atividade do solvente, dentro e fora do filme 114 . Depois do trabalho pioneiro de Buttry et al 115 nesta área, numerosas publicações trataram o tema da troca iônica em polímeros eletroativos [116][117][118][119][120][121][122][123][124][125][126][127][128][129][130][131] . Basicamente, a MECQ é utilizada para o caso da aproximação para filmes finos em estudo de cinética de eletropolimerização, assim como no estudo dos processos redox dos polímeros eletroformados.…”