Non-steady-state electrical properties in dielectric elastomer nanocomposites during cyclic stretching and the underlying mechanism

Dielectric elastomer generator (DEG) with the advantages of lightweight, flexible structure and excellent energy harvesting abilities, can supply electrical energy to portable electronic devices. Sustained high performance of DEGs requires dielectric elastomer (DE) nanocomposites to retain superior electrical properties—high insulation, breakdown strength, and dielectric constant—during dynamic stretching cycles. Nevertheless, the non-steady-state electrical properties (NEP) of DE composites under dynamic cyclic stretching, critical for long-term performance, remain insufficiently explored. Here, NEP of nanosilicon dioxide/butadiene rubber (SiO₂/BR) composites under cyclic stretching is characterized, revealing a distinct evolution mechanism: initial cycles induce interfacial molecular chains to reorient from a surface-lying state to one perpendicular to SiO₂ surfaces, enhancing insulation and breakdown strength via a 3.7-fold increase in interfacial thickness and modulus (from 4.44 MPa to 8.93 MPa). Within 60,000 initial cycles, these changes significantly boost insulation and breakdown strength. However, as fatigue accumulates, crosslink network breakage increases microdamage and chain mobility, reversing these trends and reducing insulation and breakdown strength. Integrating infrared dichroism, atomic force microscopy with quantitative nanomechanical mapping (AFM-QNM), and broadband dielectric spectroscopy (BDS), this work establishes correlations between microstructure and NEP under dynamic conditions, advancing understanding beyond static or single-parameter studies. It provides guidance for fabricating DE composites with high energy harvesting performance and long fatigue life.