Encapsulated Phase Change Material Embedded by Graphene Powders for Smart and Flexible Thermal Response

Flexible responsive materials, such as graphene embedded phase change material (PCM), can exhibit a smart response to the heating and cooling steps and be utilized for the thermal sensing applications. The electrical conductivity is varied during the phase transition due to volume change of the working material. However, the leakage is one of the serious problems and restricts the PCM from applications. Phase change material was encapsulated in the present work to prevent the leakage problem. Polyaniline (PANI) was selected as the supporting material to surround the pure phase change material and thus the fabricated PCM composite could sustain the shape under the phase transition process. Herein, the polyaniline encapsulated phase change material was produced and the graphene powder was added to increase the electrical property of the PCM composite. The graphene embedded PCM composite showed excellent electrical performance when the temperature was increased to the isothermal phase transition state. The pure PCM inside the microcapsule began to melt and the liquid state lead to the volume expansion of the PCM composite. Therefore, the reversible form stable phase transition was achieved and the electrical conductivity was increased as the distance between conductive graphene fillers was reduced with volume expansion of the PCM. This study suggests that the microencapsulated PCM composite should provide new applications for thermal sensing and flexible thermo-electric devices like smart photodetectors.