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

Abstract

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.

Robust PEDOT:PSS Wet‐Spun Fibers for Thermoelectric Textiles

“…Considering the fiber thinning during tensile stretching due to the Poisson effect, it is clear that the dimension‐normalized electrical conductivity is increased by stretching, which can be attributed to the alignment of PEDOT chains induced by tensile strain (Figure 2a,b). 13,29 To further examine how PEDOT:PSS fibers respond to repeated mechanical stress, we carried out a series of cyclic tensile deformation and bending tests. Cyclic tensile deformation with a maximum strain of 5%, i.e., at ε yield , only causes a marginal (<10%) increase in resistance after 100 cycles (Figure 2c).…”

“…Many applications require the integration of a myriad of miniaturized sensors, which would become considerably less cumbersome if each device was designed to operate autonomously without the need for batteries. A variety of electronic textiles (i.e., e‐textiles) have been demonstrated that can generate power in situ by exploiting the photovoltaic,1,2 piezoelectric,3–6 triboelectric,7,8 or thermoelectric effect 9–13. Thermoelectric textiles are particularly intriguing because they would open up the possibility to harness body heat for electricity generation.…”

“…A variety of electronic textiles (i.e., e-textiles) have been demonstrated that can generate power in situ by exploiting the photovoltaic, [1,2] piezoelectric, [3][4][5][6] triboelectric, [7,8] or thermoelectric effect. [9][10][11][12][13] Thermoelectric textiles are particularly intriguing because they would open up the possibility to harness body heat for electricity generation. At the same time, such textiles would allow to regulate the wearer's body temperature as they transport heat away from the skin to the typically colder surroundings.…”

Rubbing and Drawing: Generic Ways to Improve the Thermoelectric Power Factor of Organic Semiconductors?

“…Adapted with permission. [3] Copyright 2019, American Chemical Society b) Experimental data on PBTTT from Ref. [5] showing the anisotropy of the electrical conductivity and thermopower as a function of the alkyl side chain length at a doping time of 6 min.…”

“…PEDOT:PSS fibers were spun into 10 vol% DMSOin IPA (open circles) and a fraction of samples was subsequently drawn through a DMSO bath (filled circles). Adapted with permission [3]. Copyright 2019, American Chemical Society b) Experimental data on PBTTT from Ref [5].…”