Abstract:

Linear aliphatic polymer dielectrics show increased conduction loss at elevated temperatures as thermally activated structural fluctuations modulate electronic states and facilitate charge transport. We examine how aromatic side groups with different π-electron delocalization affect structural dynamic cooperativity and charge transport. Side-group modification alters intermolecular interactions and local dynamic constraints, shifting long-range cooperative motion to localized heterogeneous fluctuations. This transition coincides with reduced collective structural fluctuations and improved local electronic-state stability, consistent with suppressed phonon-assisted carrier transport. As a result, the furan-modified polymer exhibits a statistical electronic energy fluctuation descriptor of 0.132 eV and nearly two orders of magnitude higher volume resistivity. It achieves a discharged energy density of 8.38 J cm-3 at 120 °C, approximately 45 times that of pristine polymer while maintaining a charge-discharge efficiency above 90%. It also retains an efficiency above 93% over 5 × 105 charge-discharge cycles at 200 MV m-1. Although the higher glass transition temperature of the furan-modified polymer may also contribute to its performance near 120 °C, its advantage is already evident at 25 and 80 °C, well below the glass-transition regime. This work highlights structural dynamic cooperativity as a descriptor linking molecular dynamics and charge transport in linear aliphatic polymer dielectrics.