Effect of molecular weight distribution of PSSA on electrical conductivity of PEDOT:PSS

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful conductive polymer. In this study, we investigated the electrical properties of PEDOT:PSS prepared using poly(styrenesulfonic acid) (PSSA) having different molecular weight distributions. Herein PSSA with different molecular weight distributions were successfully polymerized by free radical polymerization and atom-transfer radical polymerization (ATRP). Polydispersity index values of PSSA obtained by the free radical process and ATRP process were 2.3-2.8 and 1.2-1.6 respectively. The electrical conductivity of PEDOT:PSS was enhanced from 376 S cm ⁻¹ (prepared using free radical PSSA) to 422 S cm ⁻¹ (prepared using ATRP PSSA) when PSSA of Mn 35 000 g mol ⁻¹ PSSA was used and was enhanced from 234 S cm ⁻¹ (prepared using free radical PSSA) to 325 S cm ⁻¹ (prepared using ATRP PSSA) when PSSA of Mn 55 000 g mol ⁻¹ was used, by a factor of 15-30%. The greater the regularity of PSSA, the greater the packing density of PEDOT:PSS and consequently, charge carrier density. The improvement of packing density of PEDOT:PSS was confirmed by improvement in crystallinity of PEDOT:PSS by X-ray diffraction (XRD) analysis.