Shear-Responsive Sol-Gel Transition of Phase Change Material Emulsions for an Injectable Thermal Insulation Platform

Phase change materials (PCMs) have attracted significant attention as promising insulating materials. However, they often suffer from the simple yet critical problem of leakage in practical applications. Therefore, in this study, an injectable PCM emulsion insulation platform is developed. For this, n-hexadecane, as a PCM, emulsion droplets are armored with a metal-organic membrane (MOM) through the coordination of zinc ions and phytic acid. The MOM layer not only provides a rigid interfacial modulus but also allows the emulsion to exhibit viscoelastic behavior by shear stress-induced interdrop association. This MOM-enveloped PCM emulsion (PCMEMOM) exhibited typical sol-gel transition behavior in response to applied shear stress, indicating the injectable characteristic of the PCMEMOM. After observing the rheological hysteresis and thermal stability of the PCMEMOM under repetitive heating and cooling cycles, the thermal insulation performance of PCMEMOM is quantitatively and visually demonstrated. These findings suggest an efficient method to exploit high-performance insulation systems.