Microwave Properties of Coplanar Waveguide-Based PEDOT:PSS Conducting Polymer Line in Ethanol Gas Atmosphere.

Hee-Jo Lee,Nathan Jeong,Hyang Hee Choi

doi:10.3390/ma13071759

Hee-Jo Lee, Nathan Jeong + Show 1 more

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https://doi.org/10.3390/ma13071759

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Abstract

This study aims to investigate the microwave properties of coplanar waveguide (CPW)-based poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) conducting polymer line in an ethanol gas atmosphere, with the frequency range of 0.5–2 GHz. For an ethanol-exposed PEDOT:PSS line (test sample), the transmission coefficient (S21) decreased immediately; moreover, the microwave effective conductivity (σm/w) decreased simultaneously, compared with the ethanol-free PEDOT:PSS line (reference sample). The immediate variations in ΔS21 ( = S21,ethanol − S21,free) and Δσm/w ( = σm/w,ethanol − σm/w,free) were approximately 10.2 dB and 2.7 × 104 S/m, respectively. Furthermore, in the analysis of the circuit model of the PEDOT:PSS line, the characteristic impedance and distributed elements, i.e., resistance (R) and inductance (L) per length, of the test sample increased, compared with the reference sample. However, upon stopping the exposure to ethanol gas, the microwave properties of the test sample instantaneously recovered to those of the reference sample. According to these critical observations, we could confirm that the coplanar waveguide with a PEDOT:PSS line shows a significant difference in the diverse microwave properties, through rapid response to the ethanol gas at room temperature.

Highlights

Polymers have typically been used as insulating materials, but with the discovery of conducting polymers (CPs), they have been used as conductive materials as well
We have observed a degradation of the S21 -level and microwave effective conductivity of the PEDOT:PSS line, with and without exposure to ethanol gas, in the observed frequency region of 0.5–2 GHz
Upon exposure to ethanol gas, the S21 -level on the PEDOT:PSS line was lowered by approximately 25% in comparison to that of the ethanol-free PEDOT:PSS line

Summary

Introduction

Polymers have typically been used as insulating materials, but with the discovery of conducting polymers (CPs), they have been used as conductive materials as well. The presence of conjugated π-electrons in CPs confers unique electrical and optical properties, including low ionization potential, high electron affinity, and low energy optical transition [2,3]. First of all, these properties were used to enhance the performance of sensors relaying on various transducers [4,5,6,7], e.g., potentiometric, amperometric, piezoelectric, calorimetric, thermal, and optical mode. Owing to the CPs processability and metallicity, some researchers conducted studies on microwave conductivity-based technology and its applications, such as electromagnetic interference shielding [11], electrostatic charge dissipation or antistatic [12], microwave absorption [13], and radar cross-section

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