A Combined XRD, Solvatochromic, and Cyclic Voltammetric Study of Poly (3,4-Ethylenedioxythiophene) Doped with Sulfonated Polyarylethersulfones: Towards New Conducting Polymers

Abstract

Despite the poor solubility in organic solvents, poly (3,4-ethylenedioxythiophene) (PEDOT) is one of the most successful conducting polymers. To improve PEDOT conductivity, the dopants commonly used are molecules/polymers carrying sulfonic functionalities. In addition to these species, sulfonated polyarylethersulfone (SPAES), obtained via homogeneous synthesis with different degrees of sulfonation (DS), can be used thanks to both the tight control over the DS and the charge separation present in SPAES structure. Here, PEDOTs having enhanced solubility in the chosen reaction solvents (N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and N-methyl-2-pyrrolidone) were synthesized via a high-concentration solvent-based emulsion polymerization with very low amounts of SPAES as dopant (1% w/w with respect to EDOT monomer), characterized by different DS. The influence of solvents and of the adopted doping agent was studied on PEDOT_SPAESs analyzing (i) the chemical structure, comparing via X-ray diffraction (XRD) the crystalline structures of undoped and commercial PEDOTs with PEDOT_SPAES' amorphous structure; (ii) solvatochromic behavior, observing UV absorption wavelength variation as solvents and SPAES' DS change; and (iii) electrochemical properties: voltammetric peak heights of PEDOT_SPAES cast onto glassy carbon electrodes differ for each solvent and in general are better than the ones obtained for neat SPAES, PEDOTs, and glassy carbon.

Role of Doping Agent Degree of Sulfonation and Casting Solvent on the Electrical Conductivity and Morphology of PEDOT:SPAES Thin Films

“…PEDOT solutions doped with SPAES_0.75 (PEDOT:SPAES_0.75) and SPAES_2.4 (PEDOT:SPAES_2.4) were obtained by high concentration solvent-based emulsion polymerization of EDOT in the presence of SPAES (1% w / w with respect to EDOT) as doping agent, ferric sulphate as radical initiator and by varying the reaction solvent, i.e., DMF, DMAc, DMSO, and NMP. Here, all PEDOT:SPAES polymer solutions have excellent miscibility in each reaction solvent and appear brown in the case of DMF, orange for DMAc, green with DMSO, and purple in NMP ( Figure 4 ), according to SPAES solvatochromic behavior [ 35 ]. On the other hand, in agreement with Sabatini et al [ 34 , 35 ], undoped PEDOT is not soluble in the selected solvents and therefore it cannot be used as reference during the discussion of the data obtained.…”

“…SPAES_0.75 and SPAES_2.4 were used as PEDOT doping agents. The reaction between PEDOT and SPAES was performed varying the reaction solvent, i.e., DMF, DMAc, DMSO, or NMP, according to our previous works [ 31 , 35 ]. In brief, a 50 cm 3 glass test tube equipped with magnetic stirring was loaded with EDOT (2.50 g), Fe 2 (SO 4 ) 3 ·xH 2 O (5 g) as radical initiator, SPAES (0.025 g) at 1% w / w with respect to EDOT monomer and the reaction solvent (3 cm 3 ).…”

“…In our previous works [ 34 , 35 ], it was reported that SPAES can be successfully used as a PEDOT doping agent. Here, for the first time, a correlation between the SPAES DS and the electrical conductivity of PEDOT: SPAES thin films obtained via spin-coating using different polar aprotic solvents is established.…”

Cost Effective Chemical Oxidative Synthesis of Soluble and Electroactive Polyaniline Salt and Its Application as Anticorrosive Agent for Steel

“…Solvatochromism is the property of a chemical substance to change color with the change of solvent polarity. The solvatochromic shift of a chromophore reflects a strong relation between solvent polarity with the absorption and emission spectra [25,26]. The solutions of PANI in different solvents are shown in Figure 2.…”

Highly Selective and Reproducible Electrochemical Sensing of Ascorbic Acid Through a Conductive Polymer Coated Electrode

“…Conducting polymer based sensors offer attractive advantages. They are effective at room temperature, diverse in structure and easy to fabricate [16,17,18]. The conducting polymer polyaniline (PANI) has exceptional properties, including stable mechanisms of electrical conduction, reversible and simple doping–dedoping ability, easy synthesis, high environmental stability and low cost.…”