Effect of gamma radiation on the transport and structural properties of polyacrylonitrile-lithium bis(oxalato)borate films

Different doses of gamma-rays from 5 to 35 kGy have been used to irradiate solid polyacrylonitrile (PAN)-lithium bis(oxalato)borate (1:1 ratio) films in order to study their transport and structural characteristics. Impedance data show that with an increase of radiation dose, conductivity (σ) of the complexes increases and exhibits a maximum of 1.02 × 10− 4 S cm− 1 at γ-ray dose of 15 kGy. The obtained conductivity is about 200 times higher than that of the virgin sample (σ = 1.74 × 10− 6 S cm− 1). By fitting the Nyquist plots with the impedance of an equivalent circuit, it is possible to calculate the dielectric constant (εr), diffusion coefficient (D), ionic mobility (μ) and mobile ion number density (n). These parameters are highest for 15 kGy irradiated samples indicating that σ, εr, D, μ and n are dependent on radiation dose. FT-IR spectroscopy confirms that ɣ-irradiation causes IR peak shifting, abolishment and reformation of functional groups of PAN-LiBOB indicating bond breaking, bond deformation and/or new bond formation. At 25 and 35 kGy doses of ɣ-radiation, new peaks have been observed at 833, 877, 1072, 1160 and 1225 cm− 1 which may be attributed to the formation of new species. Free and contact ions in irradiated films have been calculated via deconvolution of the FTIR spectra obtained from 1750 to 1850 cm− 1. The sample irradiated with 15 kGy ɣ-radiation contains the highest percentage of free ions and the lowest concentration of contact ions. The number density of free ions is observed to have more control on the conductivity compared to ion mobility and diffusion coefficient. XRD spectrum reveals peaks at 2θ ~ 16.85°, ~ 30.5° and ~ 36.9° for all irradiated samples. The polymer electrolyte irradiated with 15 kGy gamma-rays is the most amorphous. The FWHM values increase with ɣ-ray doses showing maximum at 15 kGy and then decreases with further increase of radiation dose. Crystallite size decreases with the increase of radiation doses, reaches lowest value at 15 kGy followed by additional growths as more radiation is applied. This observation is also conceivable with the EIS and FT-IR results.