Single-Chain Inherent Elasticity Reveals γ-Irradiation-Induced Backbone Reconstruction in Poly(Vinylidene Fluoride)

γ-Irradiation significantly alters the mechanical properties and functions of poly(vinylidene fluoride) (PVDF), yet the molecular mechanism underlying its property evolution at high irradiation dose remains unclear. Because the single-chain inherent elasticity of a polymer directly reflects its backbone structure, single-molecule force spectroscopy (SMFS) was employed to examine PVDF under different γ-irradiation doses. The results show a progressive increase in chain flexibility with increasing dose. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy reveal the formation of oxygen-containing groups accompanied by C═C bonds. By quantitatively correlating SMFS measurements with theoretical elasticities derived from quantum mechanical calculations, we provide the first single-molecule-level evidence that prolonged high-dose irradiation (2000 kGy) reconstructs the PVDF backbone into an alternating ether (C─O─C) and double-bond (C═C) architecture. This work establishes a direct link among irradiation dose, backbone transformation, and mechanical response, offering molecular insight into the irradiation regulation of PVDF for applications in extreme radiation environments.