Static–Dynamic Hybrid Covalent Networks Enable Scale‐Selective Molecular Confinement in Ultraflexible Phase Change Composites for Adaptive Thermal Management

Phase change materials (PCMs) offer high latent heat and near‐isothermal heat storage and release, making them attractive for thermal energy storage and regulation. However, melt leakage, low thermal conductivity, and solid‐state rigidity hinder the simultaneous achievement of dimensional stability, flexibility, interfacial adaptability, and multifunctional responsiveness at high energy‐storage densities. Here, we develop ultraflexible paraffin‐based composite phase change materials (CPCMs) using a hybrid static–dynamic covalent three‐dimensional network and graphene nanoplatelets (GNPs) as rapid heat‐transfer pathways. Static covalent bonds maintain network integrity, while exchangeable boronic ester moieties enable thermally triggered rearrangement. Experiment and simulation results demonstrate the cross‐linked network suppresses large‐scale cooperative migration of paraffin while preserving the local degrees of freedom required for reversible phase transitions. The resulting CPCM delivers a phase‐change enthalpy of 172.2 J/g and an ultra‐high fracture elongation of 1219.5%. GNP incorporation increases thermal conductivity to 2.07 W/m·K while retaining an enthalpy efficiency over 98.8%, together with excellent adhesion, self‐healing, recyclability, and shape memory. The material further enables efficient thermal regulation in electronics, wide‐temperature‐range batteries, solar thermal storage, and flexible wearable thermal management. This strategy provides a novel design route toward integrating high energy storage, ultraflexibility, structural stability, and dynamic interfacial adaptability in one phase‐change material system.