Harrick PlasmaRS: Conducting Polymer

Conducting Polymers (CP), such as polypyrrole (pPy), are promising materials with potential applications as electrochemical energy storage devices, actuators and biosensors due to their conductivity, redox activity and biocompatibility. Success in these applications depends on the polymer thickness and stability; thicker pPy layers offer increased charge storage capacity while mechanical stability is critical for long term use. Due to poor adhesion between CP and the underlying electrode material, researchers have been unable to achieve high CP performance. To address this, various processing techniques have been attempted to achieve stronger adhesion, including chemical etching to improve mechanical interlocking as well as covalently bonding pyrrole monomers to the electrode. However, these methods tend to degrade the overall stability of CP. To be able to utilize conducting polymers in practical applications, their interfacial adhesion must be improved while retaining their physical and electrochemical performance.

To enhance the interfacial adhesion of polypyrrole with gold electrodes, plasma treatment and an intermediate coating of polyethyleneimine (PEI) was recently shown to be a critical step. In the Scientific Reports article, Sung Yeol Kim’s group at Kyungpook National University attempted to create thicker and stronger pPy by introducing an adhesion enhancing layer between the conducting polymer and the metal electrode. Using Harrick Plasma’s Basic Plasma Cleaner, they removed organic contamination from the electrode surface and introduced polar carbonyl functional groups to facilitate PEI physisorption. Ultimately, they found that plasma treated gold electrodes coated with PEI (PEI-O2 Au) were the optimal substrate for pPy electrodeposition, outperforming both bare gold electrodes and untreated PEI coated electrodes. They proposed that the polar groups on the plasma-treated electrode surface attracted the positively charged pPy, entangling the pPy backbone with PEI and further enhancing adhesion. As a result, they were able to produce stable pPy layers twice as thick as bare electrodes without reducing electrochemical performance.

Kim KG, Kim SY. “Increase in Interfacial Adhesion and Electrochemical Charge Storage Capacity of Polypyrrole on Au Electrodes Using Polyethyleneimine”. Sci Rep. (2019) 9: 6346.

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