Adjustable comb/bottlebrush fast UV-curable epoxy-based form-stable phase change materials with high encapsulation rates and ultralow enthalpy loss

Abstract

High encapsulation rates resulting from excellent compatibility between encapsulated solid–liquid phase change materials (SLPCMs) and cross-linking networks usually lead to high enthalpy loss for polymeric form-stable phase change materials (FSPCMs). Besides, the traditional thermal curing process for preparing polymeric FSPCMs requires a long time and causes much energy consumption. Therefore, the integration of a high encapsulation rate, low enthalpy loss, and an efficient photocuring strategy for designing polymeric FSPCMs is still a challenge. In this work, a series of fast ultraviolet (UV) curable and adjustable comb/bottlebrush epoxy/paraffin FSPCMs with high encapsulation rates and low enthalpy loss were designed and highly efficiently prepared through the chain extension reaction of epoxy resin and octadecylamine (ODA) followed by a photoinitiated thiol–ene click curing reaction. By adjusting the physical entanglement of the molecular chains, compatibility between the 3D cross-linking network and paraffin, and chemical cross-linking density, a high encapsulation rate of paraffin (60 wt%) and ultralow enthalpy loss (0.7%) can be achieved in only 13 min of the photocuring process, and the enthalpy value of the FSPCMs can reach 150.1 J g⁻¹. The effects of the molecular weight, grafting density, and cross-linking density on the phase change properties were systematically discussed. Subsequently, through the introduction of Diels–Alder (D–A) bonds, the recycling and self-healing ability of the epoxy/paraffin FSPCMs was further achieved. This paper not only provides a strategy for preparing polymeric FSPCMs by the fast photocuring process but also can provide theoretical guidance for the optimization of the preparation of self-healing polymeric FSPCMs with high encapsulation rates and ultralow enthalpy loss.