Cloud point temperature (Tcp) is a thermal index used to define the phase transition of thermoresponsive polymers. In this study, we used electrochemical techniques to obtain an electrochemical cloud point temperature (Tecp) that exhibits the more accurate phase transition temperature and can replace Tcp. Thermoamperometry on an ultramicroelectrode was conducted with a poly(arylene ether sulfone) (PES10) as a model system to obtain a current-temperature (i-T) curve in real time; the Tecp of the PES10 was determined from the i-T curve. The i-T curve shows an unprecedented current decrease in the PES10 solution despite increasing temperature; on the other hand, the current increased linearly with increasing temperature in the solution without PES10. This phenomenon was analyzed by considering the characteristics of PES10 during phase transition, such as dynamic viscosity, temperature of the solution, and electrode impedance. It was confirmed that the current drops shown in the i-T curves were mainly due to the decrease of real electrode area. The comparison of Tecp and Tcp showed that both depended similarly on the concentrations of the thermoresponsive polymer and the supporting electrolyte. The results reveal that by adjusting the concentration of polymer and electrolyte in an organic solution, Tecp, as a new analytical method, can be used in electric circuit-based energy storage appliances such as Li-ion batteries and supercapacitors.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean Government (MSIT) (NRF-2021R1A2C4002069 and NRF-2021R1A4A1052070). This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2021R1A6A1A10039823) and Institutional Research Program (SI2252-20) of the Korea Research Institute of Chemical Technology (KRICT).
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