Dynamic Covalent Adaptable Polyimide Hybrid Dielectric Films with Superior Recyclability

Abstract

Polyimides (PIs) used in advanced electrical and electronic devices can be electrically/mechanically damaged, resulting in a significant waste of resources. Closed‐loop chemical recycling may prolong the service life of synthetic polymers. However, the design of dynamic covalent bonds for preparing chemically recyclable crosslinked PIs remains a challenging task. Herein, new crosslinked PI films containing a PI oligomer, chain extender, and crosslinker are reported. They exhibit superior recyclability and excellent self‐healable ability owing to the synergistic effect of the chain extender and crosslinker. The produced films can be completely depolymerized in an acidic solution at ambient temperature, leading to efficient monomer recovery. The recovered monomers may be used to remanufacture crosslinked PIs without deteriorating their original performance. In particular, the designed films can serve as corona‐resistant films with a recovery rate of approximately 100%. Furthermore, carbon fiber reinforced composites (CFRCs) with PI matrices are suitable for harsh environments and can be recycled multiple times at a non‐destructive recycling rate up to 100%. The preparation of high‐strength dynamic covalent adaptable PI hybrid films from simple PI oligomers, chain extenders, and crosslinkers may provide a solid basis for sustainable development in the electrical and electronic fields.

Constructing Fluorine Hybrid Epoxy Polymers with Excellent Breakdown Strength by Surface Fluorination

“…The chemical structures are closely connected to the dielectric trap in organic polymers. ,− , Scholars reported that the trap level was influenced by the charge distribution in molecules − , and thus Yang and Wang used Mulliken charge distribution to study the relationship between molecular chemical structure and trap level. Given that, in this study, based on the FTIR and XPS experimental results, we established the molecular models of EP and fluorination EP, and revealed the relationship between chemical structure and trap level from the perspective of molecular Mulliken charge distribution.…”

“…The atom with positive charge can be treated as the electron trap in the molecules, and can attract and capture the free electrons or other negative charges nearby. 18,[22][23][24]44,45 The greater charge quantity signifies a stronger ability to capture carriers by Coulombic force. 12,13 After introducing CF 3 groups into the EP molecule, the MPMC is increased by 48.55% from 0.655 to 0.973 eV.…”

“…As seen in Figure S3d, the Mulliken charges of the three F atoms are −0.327, −0.326, and −0.336 eV, and the Mulliken charge of the C atom in CF 3 group is 0.973 eV. The atom with positive charge can be treated as the electron trap in the molecules, and can attract and capture the free electrons or other negative charges nearby. ,− ,, The greater charge quantity signifies a stronger ability to capture carriers by Coulombic force. , After introducing CF 3 groups into the EP molecule, the MPMC is increased by 48.55% from 0.655 to 0.973 eV. The C atom from the CF 3 group with a superior positive Mulliken charge can attract the free electrons with stronger Coulombic force.…”

“…The charge transport process in dielectrics is influenced by the trap level and many scholars have proposed their models to study the relationship between trap level (energy) and electrical breakdown. ,− In this study, based on previous studies, ,− we established the schematics in Figure c,d to interpret the influence of the greater trap level on increasing breakdown strength of fluorinated EP. The electrical breakdown process in solid dielectrics including electron injection, migration, impact ionization, electron multiplication and avalanche, etc. − Among these complex processes, dielectric trap plays an important role and can influence the electron migration, ionization, and multiplication processes.…”

Peelable Microwave Absorption Coating with Reusable and Anticorrosion Merits

“…48 The higher slopes are perceived in SLCP15, SLCP20, and SLCP25 specimens, manifesting the enhanced conductive loss induced by the electron's migration/ hopping 55 within the 3D porous network structure of CNT@ PANI or that the interface of CNT@PANI (Figure 4i) plays a vital role in dissipating the microwave. Meanwhile, the difference of electrostatic potential distribution calculated by density functional theory (DFT) (Figure 4i) would further promote the electrons' migration 56 to enhance the conductive loss, and the existence of positive and negative potentials as the active sites would be conducive to polarizations. 57 For the SL(C + P) specimen, the pure CNT without a well-designed impedance matching layer (PANI) is endowed with high conductivity due to the free electrons migrating through its surface according to the skin effect, which leads to a major electromagnetic wave reflection on the surface.…”