Heterocyclic aramid-based phase-change films fabricated via the oil-in-oil emulsion technology with multiple energy conversion, thermal regulation, and electromagnetic shielding properties

Abstract

Phase-change materials (PCMs) have demonstrated significant potential in solar energy utilization and thermal management owing to their high energy density and isothermal phase transition. Nevertheless, inherent leakage risks and limited energy sources hinder their widespread application. Herein, multifunctional heterocyclic aramid-based phase-change films doped with n-octadecane (OD) were prepared using an oil-in-oil emulsion template and an emulsion coating technique. In this process, OD was encapsulated using a composite matrix composed of heterocyclic aramid (HA), carbon fibers and carbon nanotubes, forming an OD-in-HA/C non-aqueous emulsion, followed by emulsion coating to yield flexible HA/C/OD phase-change films. The resulting HA/C/OD films exhibited good mechanical strength (5.1 MPa), high enthalpy (92.8 J g⁻¹), minimal supercooling, and almost no leakage. Their superior phase-transition properties remained stable even after 80 thermal cycles. Moreover, the embedded carbon nanotubes and carbon fibers imparted high electrical conductivity, efficient electro- and photo-thermal conversion, and hydrovoltaic electricity generation. By leveraging their combined latent heat and conductivity, these films also served as ideal candidates for information encryption and electromagnetic shielding. This research provides an innovative and scalable strategy for preparing multifunctional polyamide-based PCMs, paving the way for efficient energy utilization and conversion.