Fabrication of a Dynamic Energy Dissipation Hierarchical Noncovalent Network for Folding Resistances

The emerging stress-induced buckling failure in the ultra-thin flexible displays market demands innovative solutions for enhanced reliability. This study develops a hierarchical dynamic cross-linking network via hydrogen bonding/metal coordination/cation-π synergism in colorless poly(amide-imide) (CPAI) films, enabling cross-scale stress equilibrium. Multiscale characterization coupled with MD simulations unravel the tri-modal dissipation mechanism in calcium-modified CPAI (CPAI-Ca): hydrogen bonds serve as primary energy dissipation units, while the dynamically reversible metal coordination bonds (with 1.98-6.59 Å extensible/compressible slip space) and cation-π interaction networks (forming a broad stress buffer zone of 6.59-9.82 Å) collaboratively establish multiscale energy dissipation pathways through molecular chain slip. The optimized CPAI-Ca withstands 200 000 folds at 0.5 mm radius (10x improvement over conventional CPAI) while suppressing buckling deformation by 92.8%. A real-time monitoring system reveals minimal resistance variation (ΔR/R₀ = 7.35%) and uniform stress distribution after 200 000 commercial-scale folding cycles (r = 1 mm). The material concurrently achieves outstanding thermal stability (T_g = 398.77 °C), high optical transparency (T₅₅₀ = 89.38%), and remarkable modulus (E = 5.47 GPa). This multifunctional integration establishes CPAI-Ca as an innovative material solution for ultrathin flexible display applications.