Electrochemically-Obtained Polysulfonic-Acids Doped Polyaniline Films—A Comparative Study by Electrochemical, Microgravimetric and XPS Methods

Abstract

Polyaniline (PANI) layers are electrochemically obtained in the presence of four polysulfonic acids with different rigidities of the polymer backbone-iso-(and tere-)poly-(4,4′-(2,2′-disulfonic acid)-diphenylene-iso(tere)-phthalamide (i-PASA and t-PASA), polystyrenesulfonic acid (PSSA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA). Combined microgravimetric (EQCM) and electrochemical measurements are carried out in the course of polymerization and repetitive redox switching. It is found that after synthesis PASA-doped PANIs shows good stability with low exchange of mass in the course of voltammetric scans, while PAMPSA-doped PANI contains a large amount of water that gradually becomes expelled in the repetitive redox switching. PANI obtained in the presence of PSSA takes an intermediate position with respect to mass exchanged in the electrochemical redox process. XPS studies are used to obtain data for the extent of doping of the different PANI materials. The results show high doping level (about 0.5) for PASA- and PAMPSA- and lower level (0.32) for PSSA-doped PANI layers. Repeated electrochemical studies carried out with the specimens investigated by XPS after long-term storage in the dry state give evidence for structural rearrangement, perfect recuperation of the initial electrochemical activity and high stability of the electrochemical response.

Electrochemically Obtained Polysulfonates Doped Poly(3,4-ethylenedioxythiophene) Films—Effects of the Dopant’s Chain Flexibility and Molecular Weight Studied by Electrochemical, Microgravimetric and XPS Methods

“…Furthermore, accommodation of the polymer structure occurring at the repetitive redox transitions may be related to loss of solvent molecules. Such effects were already observed for PASA- and PSSA-doped polyaniline layers [ 35 ].…”

Enhanced Chemical and Electrochemical Stability of Polyaniline-Based Layer-by-Layer Films

“…One of the ways to increase the chemical and electrochemical stability of PANI is to dope it using large molecule polyacids, instead of small molecule anion dopants [ 1 , 13 , 14 , 15 ]. The Loo Group reported that electroactivity and electrochemical stability can be enhanced by doping PANI using a strong polyacid, poly(2-acrylamide-2-methyl-1-propane sulfonic acid (PAAMPSA)), showing that PANI can reversibly change its oxidation state in neutral and alkaline aqueous solutions [ 9 ].…”

Polysulfonate-doped polyanilines—oxidation of ascorbic acid and dopamine in neutral solution

“…It is known that PANI doped with inorganic ions loses its conductivity for pH > 3 due to decrease of the number of protonated amine species. This drawback was overcome by two different strategies-so-called self-doping (i.e., chemical modification of the main polymer chain to obtain covalently bound acid moieties such as sulfonates or phosphonates) [6][7][8][9][10][11][12][13][14][15][16] and doping by monoorganic acid or poly(organic acid) anions that become steadily immobilized in the PANI structure [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

“…Overlapping double peaks were still distinct in the reductive wave [31]. In the recent years, a series of papers [23,[26][27][28][32][33][34] was devoted to the properties of PANI obtained in the presence of two poly(amidosulfonic acids) that are identical in their chemical composition but differ in the rigidity of their backbone-poly-(4,4′-(2,2′-disulfonic acid)-diphenylene-tere-phthalamide) (t-PASA, rigid backbone) and poly-(4,4′-(2,2′-disulfonic acid)-diphenyleneiso-phthalamide) (i-PASA, semi-rigid backbone). It was shown [26] that PANI/PASA-doped layers retain some extent of electroactivity up to pH 5 but the initial charge is partially lost after treatment in the slightly acidic solutions.…”

“…It was shown [26] that PANI/PASA-doped layers retain some extent of electroactivity up to pH 5 but the initial charge is partially lost after treatment in the slightly acidic solutions. PASA-doped PANI were extensively studied with respect to their chemical and electrochemical polymerization [27,28,32], spectroelectrochemical response [33], surface morphology [23,32], and extent of doping [34] but no information is available on their behavior in neutral solutions and potential electrocatalytic properties in these media.…”