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

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.