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<p>In general, the design of polymer dielectrics relies on the classical “band-gap criterion,” according to which a larger electronic band gap (<i>E</i><sub>g</sub>) is typically associated with a higher breakdown strength (<i>E</i><sub>bd</sub>). However, in hydrogen-bond-containing polypropylene-graft-maleic acid/poly(vinylidene fluoride) (PP-g-MA/PVDF) composites, this study identified a distinct phenomenon: as the number of hydrogen bonds increased, the electronic band gap decreased significantly from 4.76 to 3.86&#xa0;eV, whereas the breakdown strength increased from 53.30 to 76.20&#xa0;kV/mm, corresponding to an increase of 42.96%. To investigate the possible microscopic mechanism underlying this phenomenon, first-principles quantum-chemical calculations were employed to analyze the hydrogen-bond-induced reconstruction of the electronic structure. The results revealed that hydrogen-bond formation was accompanied by pronounced interfacial charge redistribution, interatomic electronic interactions, and changes in the local electronic structure, which were consistent with an increase in localized electronic states near the conduction-band edge. This profound reconstruction of the electronic structure led to a 210% increase in the maximum density of states (DOS<sub>max</sub>) within a specific energy range, extending from the conduction band minimum (CBM) to the conduction band minimum plus the band gap (CBM + <i>E</i><sub>g</sub>). Based on a modified von Hippel avalanche model, this study theoretically elucidated that an increase in DOS<sub>max</sub> may provide additional inelastic electron–phonon scattering channels, thereby helping to suppress the development of electron avalanches. Further validation through simulations, experimental breakdown measurements, and multiple statistical analyses showed that DOS<sub>max</sub> exhibited a stronger correlation with breakdown strength than <i>E</i><sub>g</sub>. Therefore, even when the band gap decreases, an increase in DOS<sub>max</sub> near the conduction-band edge may still contribute to suppressing electron-avalanche development and improving breakdown performance. This study provides a physical framework for understanding breakdown phenomena in complex polymer systems and proposes a polymer-dielectric design strategy that synergistically considers conventional “band-gap regulation” and “conduction-band-edge density-of-states regulation.”</p>

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Influence mechanism of hydrogen-bond-modulated electronic density of states on the breakdown properties of PP-g-MA/PVDF composites

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月1日

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  • Yulong Wang,
  • Shuang Han,
  • Bojia Hou,
  • Binrui Yang,
  • Lin Liu,
  • Lili Li,
  • Junguo Gao

摘要

In general, the design of polymer dielectrics relies on the classical “band-gap criterion,” according to which a larger electronic band gap (Eg) is typically associated with a higher breakdown strength (Ebd). However, in hydrogen-bond-containing polypropylene-graft-maleic acid/poly(vinylidene fluoride) (PP-g-MA/PVDF) composites, this study identified a distinct phenomenon: as the number of hydrogen bonds increased, the electronic band gap decreased significantly from 4.76 to 3.86 eV, whereas the breakdown strength increased from 53.30 to 76.20 kV/mm, corresponding to an increase of 42.96%. To investigate the possible microscopic mechanism underlying this phenomenon, first-principles quantum-chemical calculations were employed to analyze the hydrogen-bond-induced reconstruction of the electronic structure. The results revealed that hydrogen-bond formation was accompanied by pronounced interfacial charge redistribution, interatomic electronic interactions, and changes in the local electronic structure, which were consistent with an increase in localized electronic states near the conduction-band edge. This profound reconstruction of the electronic structure led to a 210% increase in the maximum density of states (DOSmax) within a specific energy range, extending from the conduction band minimum (CBM) to the conduction band minimum plus the band gap (CBM + Eg). Based on a modified von Hippel avalanche model, this study theoretically elucidated that an increase in DOSmax may provide additional inelastic electron–phonon scattering channels, thereby helping to suppress the development of electron avalanches. Further validation through simulations, experimental breakdown measurements, and multiple statistical analyses showed that DOSmax exhibited a stronger correlation with breakdown strength than Eg. Therefore, even when the band gap decreases, an increase in DOSmax near the conduction-band edge may still contribute to suppressing electron-avalanche development and improving breakdown performance. This study provides a physical framework for understanding breakdown phenomena in complex polymer systems and proposes a polymer-dielectric design strategy that synergistically considers conventional “band-gap regulation” and “conduction-band-edge density-of-states regulation.”