Effect of Drawing on the Electrical, Thermoelectrical, and Mechanical Properties of Wet-Spun PEDOT:PSS Fibers

New electrically conducting and mechanically robust fibers and yarns are needed as building blocks for emerging textile devices. In this work, we describe a continuous wet-spinning process for the fabrication of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fibers with high electrical conductivity, excellent mechanical properties, and moderate thermoelectric performance by including a drawing stage in dimethyl sulfoxide. Drawing the fibers induced preferential orientation of the polymer chains in the fiber axis direction. With increased drawing, the room temperature electrical conductivity saturated at approximately 2000 S cm-1. The Seebeck coefficient was found to be rather constant with drawing. Therefore, the thermoelectric power factor saturated with applied draw between 40 and 50 μW m-1 K-2. The thermal conductivities of the drawn fibers were measured between 4 and 5 W m-1 K-1 at liquid nitrogen temperatures. Although the relatively high thermal conductivity negatively affects the ultimate thermoelectric performance, it can be beneficial for other applications such as in electrical interconnections. Additionally, at high draw ratios, the Young's moduli saturated at near 15.5 GPa with maximum break stresses of 425 MPa. To the best of our knowledge, this Young's modulus is the highest reported for a PEDOT:PSS material. Further, we investigated the degree of preferred orientation by wide-Angle X-ray scattering and found a strong correlation between the orientation of the polymer chains along the fiber axis and the trends observed in the fibers' properties. In general, the fibers with the highest orientation were also the stiffest and the most conducting fibers. We believe these are important steps toward the continuous fabrication of high performance PEDOT:PSS fibers to be used as building blocks in the emerging field of electronic textiles.