Boosting Discharge Energy Density of Commercially Available Polyethylene via Post-Polymerization Modification

Enhancing polymer dielectric properties is critical for more efficient and reliable energy storage, sensors, and actuators. However, achieving high dielectric constant and low dielectric loss tangent in polymer materials is challenging without incurring higher cost in comparison to polyolefins that are widely used as dielectric materials. Here, we demonstrate postpolymerization modification (PPM) of linear low-density polyethylene (LLDPE) by using azide–alkyne click chemistry to covalently attach polar amines and zwitterions to the backbone, dramatically improving dielectric performance. Amine- and zwitterion-functionalized LLDPE exhibited greater dielectric constants (ε_s = 12 and 5.6, respectively) than unfunctionalized LLDPE (ε_s = 2.8). Moreover, the trade-off in functionalizing LLDPE was minimal with the dielectric loss tangent (tan δ) increasing from 0.0002 to 0.007–0.17 at 1 kHz and 30 °C and a modest reduction in the breakdown strength. Electric displacement–electric field loop studies indicate that the discharge energy density (U_d) of amine-modified LLDPE (U_d = 1.59 J/cm³ at 150 MV/m with a high efficiency of 83.5%) outperforms that of poly(vinylidene fluoride), a high-performance ferroelectric polymer, and is 7 times greater than that of the pristine LLDPE. PPM provides a versatile approach to enhance the dielectric properties of commercially available polyolefins for capacitor applications through covalent attachment of polar functionality.