Dual Channel Ionic Transport in Conducting Polymers Influence by Hydrophobicity*

Mixed electron/ion transport in organic materials is attracting great attention due to the possibilities in applications such as electrochemical transistors, bioelectronics, sensors, and soft robotics. PEDOT:PSS shows promise as a mixed conductor with a morphology consisting of PEDOT-rich gel particles embedded within a PSS matrix. Our previous study reported a fast and a slow ion mobility channels. Here we show that the faster ion mobility occurs in a PSS-rich top layer. We used different ion barrier layers of increasing hydrophobicity to show high correlation with the measured ion mobility. We also removed the top PSS layer through water sonicating at different stages of film crosslinking which again confirms linear relation between the contact angle of the PEDOT channel and mobility. The results reveal the measured ion mobility can be skewed without taking the PSS top layer into effect. Additionally, we will discuss our investigation toward resolving where the ion goes in the nano structure during doping through resonant soft X-ray scattering measurements. Understanding the correlation between structure and ion transport to transduce an electric signal will enable these devices to potentially use in next generation medical advancement.