Diamine-PEG crosslinking engineering of PVDF: Simultaneous γ-phase crystallization control and high-frequency dielectric stabilization for flexible ferroelectrics

The γ-phase of poly(vinylidene fluoride) (PVDF) exhibits exceptional dielectric polarization and thermal stability but suffers from kinetically hindered crystallization and high-frequency dielectric losses in conventional processing. We develop a diamine-polyethylene glycol (diamine-PEG) covalent crosslinking strategy that simultaneously overcomes both limitations. The sterically confined network enables rapid γ-phase crystallization (92 % purity within 4 h at 155°C) through directed T 3 GT 3 G′ chain alignment, while suppressing parasitic dipole relaxation. This yields breakthrough dielectric performance: frequency-stable permittivity (ε' ≈ 8) with ultralow loss (tan δ = 0.21 at 10 6 Hz, 60 % reduction vs. pristine PVDF) and ferroelectric switching exhibiting 2.5-fold enhancement in polarization (4.5 μC/cm 2 at 2000 kV/cm). Crucially, the films retain exceptional flexibility (307 % elongation at break with 5 wt% crosslinker vs. 90 % for neat PVDF) and solution processability, establishing a multifunctional platform for flexible power electronics requiring concurrent high-frequency stability, thermal resilience, and mechanical durability.