Observing the Current Change with Increasing Temperature in Thermo-Responsive Polymer Solution Using Electrochemical Method

Abstract

The behavior of redox in thermo-responsive polymer solution while heating was electrochemically observed and analyzed in this research. Temperature responsive polymers are intensively applied to various research fields and industries such as drug carriers, lithium ion batteries, temperature sensitive films, and sensor technology. For this reason, measuring the critical point and analyzing the phase transition of temperature stimuli responsive polymer are very important.In previous studies, the phase behavior of polymers according to the temperature was examined by measuring the transmittance of solution using ultraviolet–visible (UV-vis) spectroscopy and the size of polymer particles in solution using dynamic light scattering (DLS). As an electrochemical method, a collision method was used for detecting current decrease caused by aggregated polymer which blocked the electrode surface. These methods, however, were unable to track the behavior of polymer in solution during continuous temperature increase in real time easily. The temperature was increased at intervals of 5 ℃ to measure the absorbance of solution in UV-vis spectroscopy and only specific temperature and time could be used to observe the blocking signal in the electrochemical collision method. In this study, we offer the easy and novel way to monitor the thermal induced change of polymer and redox with continuous temperature increase using the electrochemical system.Lower critical solution temperature (LCST) polymer was used as the thermo-responsive polymer in this research. Dissolving the LCST polymer in organic media containing the redox, we measured the current with increasing temperature in real time. The experiment was conducted using electrochemical method with an ultramicroelectrode (UME) and the current transition according to the temperature growth was monitored. As a result, the specific current changes were obtained. Analyzing these specific current changes can be used to confirm the phase transition behavior of the temperature responsive polymer and redox in polymer solution. This study will be applied for further research with controlling the various conditions.