Free volume-related microstructural properties of lithium perchlorate/sodium alginate polymer composites

Abstract

The effect of salt (LiClO4) on free volume-related microstructural, optical, and dielectric properties of lithium perchlorate (LiClO4)-doped sodium alginate (NaC6H7O6)n solid polymer electrolyte were studied using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), UV–Visible, dielectric measurements, and positron annihilation lifetime spectroscopy (PALS) techniques. The FTIR study reveal that the LiClO4 interact with the OH groups of sodium alginate (NaAlg) and forms charge transfer complex (CTC). These formed CTC within the composite film affect the optical property of the polymer composite, which was reflected from UV–Visible study. The free volume was probed by the PALS technique, which uses the o-Ps pickup lifetime τ3, as an indication of local electron density and mean free volume radius. The o-Ps pickup intensity I3, reflects the probability of o-Ps formation. The o-Ps components τ3 and I3 increases with salt concentration, which shows microstructural modifications due to the decrease in the crystallinity of the NaAlg as observed from XRD studies. Therefore, electrical studies on the doped NaAlg reveal that the ionic movement in the composites is mainly due to the segmental motion of the polymer backbone. So, the complex formation due to doping affects the free volume-related microstructure and hence the dielectric properties including the AC conductivity of the polymer composites. POLYM. COMPOS., 35:1267–1274, 2014. © 2013 Society of Plastics Engineers