Hierarchical Supramolecular Engineering of a Multifunctional Phase‐Change Material with Thermally Switchable Properties for Adaptive Thermal Management

Abstract Phase‐change materials (PCMs) are widely recognized for their excellent thermal storage performance, making them promising candidates for environmental temperature control and personal thermal management. However, it is challenging to achieve dimensional stability under complex conditions, and also maintain mechanical flexibility, interfacial adhesion, and multifunctional responsiveness. Here, we present a hierarchical and reversible supramolecular interaction‐mediated strategy to construct a multifunctional phase‐change gel (SPCG). Polyethylene glycol is encapsulated within a three‐dimensional crosslinked poly(acrylic acid‐co‐hydroxyethyl methacrylate) network, while incorporating sulfonated cellulose nanofibers establishes the hierarchy of skeleton through diverse non‐covalent interactions, and markedly enhances structural integrity. The resulting SPCG demonstrates exceptional dimensional and structural stability across different phase states, with a modulus ranging from 0.014 to 62.4 MPa, remarkable flexibility of up to 419.2%, and robust, repeated adhesion (adhesion strength of 1163.5 kPa). Furthermore, its phase transition process enables efficient latent heat storage and release (132.5 J g ⁻¹ ), providing excellent thermal regulation capabilities for wearable applications. These findings demonstrate that hierarchical supramolecular engineering can simultaneously address stability, flexibility, adhesion, and multifunctional responsiveness in a single PCM system. Moreover, our strategy offers a sustainable and scalable pathway for designing advanced PCMs, paving the way for next‐generation adaptive thermal management technologies.