*3.3.1 Mechanisms and benefits of gelling agents*

Gelling agents play a pivotal role in modifying the molecular arrangement and behavior of phase change materials (PCMs), rendering them more amenable to phase changes occurring at or near the desired temperature. These agents serve as nucleation sites within the PCM, initiating the crucial first step in the formation of solid crystals during the phase change process. By promoting nucleation, gelling agents encourage the PCM to initiate crystallization more readily, simultaneously increasing the viscosity of the PCM. This heightened viscosity hampers the movement of PCM molecules, compelling them to transition away from the supercooled state and toward the solid phase more expeditiously, effectively reducing the supercooling effect. Additionally, gelling agents lower the energy barrier necessary for nucleation and phase change processes to take place. Supercooling, a phenomenon where PCM molecules require a specific amount of energy to surmount this barrier and shift to the solid phase, is effectively mitigated by gelling agents. This reduction in the energy barrier ensures that the PCM solidifies more promptly, aligning with the intended phase change temperature. Moreover, certain gelling agents can augment the thermal conductivity of the PCM. This heightened thermal conductivity facilitates the


#### **Table 2.**

*Composition and thermophysical properties of PCM with thickener and nucleators [45].*
