Investigation of the doping efficiency of poly(styrene sulfonic acid) in poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) dispersions by capillary electrophoresis

Abstract

CE can efficiently separate poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) complexes and free PSS in dispersions and can be used to estimate the degree of PSS doping. We investigated the doping efficiency of PSS on PEDOT in dispersions using CE and its effect on the conductivity of the resulting PEDOT/PSS films. Results of this study indicate that dispersions containing 1:2.5-3 EDOT:PSS feed ratio (by weight) exhibiting 72-73% PSS doping generate highly processable and highly conductive films. Conductivity can be optimized by limiting the time of reaction to 12 h. At this point of the reaction, the PEDOT/PSS segments, appearing as broad band in the electropherogram, could still exist in an extended coil conformation favoring charge transport resulting in high conductivity. Above a threshold PEDOT length formed at reaction times longer than 12 h, the PEDOT/PSS complex, appearing as spikes in the electropherogram, most likely have undergone a conformational change to coiled core-shell structure restricting charge transport resulting in low conductivity. The optimal conductivity (5.2 S/cm) of films from dispersions synthesized for 12 h is significantly higher than those from its commercial equivalent Clevios P and other reported values obtained under similar conditions without the addition of codopants.

Imaging the Phase Separation Between PEDOT and Polyelectrolytes During Processing of Highly Conductive PEDOT:PSS Films

“…57 In recent years, using 20 mM borate buffer (pH = 9.4), Diah et al showed that "free" PSS could be separated from the Clevios P PEDOT:PSS complex. 58,59 In their experiment, the optimized PEDOT:PSS with a conductivity It is widely described that the removal of PSS from PEDOT:PSS complex enables the conductivity enhancement observed in highly conductive PEDOT films. The actual depletion of PSS from the complex was well supported by the observations from highly conductive PEDOT films prepared and processed.…”

Effective Approaches to Improve the Electrical Conductivity of PEDOT:PSS: A Review

“…The optimal conductivity value of 5.2 S cm −1 was obtained, which was signifi cantly higher than its commercial equivalent Clevios P, as well as those reported in literature obtained under similar conditions without secondary doping. [ 138 ] …”

An Assessment of the Effect of Synthetic and Doping Conditions on the Processability and Conductivity of Poly(3,4-ethylenedioxythiophene)/Poly(styrene sulfonic acid)

“…Processability of these dispersions was gauged from the quality of the corresponding films imaged using an optical microscope. Previous reports from our group have focused on the development of a CE method for PEDOT/PSS dispersions and have allowed quantification of doped and free PSS in PEDOT/PSS dispersions presented in this study.…”

“…The CE, particle size, and zeta potential analyses of the PEDOT/PSS dispersions were conducted as outlined in the previous reports …”

“…Thus, by evaluating synthetic and doping conditions, we managed to obtain an optimum conductivity of 5.2 ± 0.7 S cm −1 , without the addition of secondary dopants. Additionally, this study also presents the application of capillary electrophoresis (CE) for the evaluation of PSS doping in PEDOT:PSS dispersions that we have developed in a previous study …”