The development of a highly conductive PEDOT system by doping with partially crystalline sulfated cellulose and its electric conductivity

Abstract

Using direct sulfation of cellulose, we prepared sulfated cellulose (CS) with various degrees of substitution of sulfate groups (DS), which we used as dopants for PEDOT. PEDOT/CS were prepared via in situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) in an aqueous CS solution. Films of the obtained PEDOT/CS were formed using spin-coating. As a reference, a PEDOT/PSS film was also formed. The electrical conductivity of the PEDOT/CS film with a DS of 1.03 was 0.576 S m⁻¹. In contrast, the electrical conductivity of the PEDOT/PSS film was 0.0153 S cm⁻¹. Using Raman spectroscopy, we found that the 1400 and 1500 cm⁻¹ bands correspond to the C_αC_β vibrations in the five-member PEDOT ring. Compared with the band of the PEDOT/PSS film, the band of the PEDOT/CS film red-shifted from 1437 to 1433 cm⁻¹ and narrowed. We attributed the increased electrical conductivity of the PEDOT/CS film to a greater proportion of the quinoid structure than in PEDOT contained in PEDOT/PSS.