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The optical, electrical, and microstructurtal properties of pure and TiO 2 /Poly(vinyl alcohol) (PVA) composite polymer films were carried out using FTIR, XRD, UV-Visible, DC electrical conductivity, and Positron annihilation lifetime spectroscopy (PALS) techniques. The FTIR study reveals that the Ti 1 ions of TiO 2 interacts with the OH groups of PVA via intra/inter molecular hydrogen bonding and forms charge transfer complex (CTC). These formed CTC will affect the optical property of the composite film, which is reflected from UV-Visible study. Using the observed UV-Visible spectra, optical energy band gap is estimated and its value decreases with increasing dopant concentration. The positron annihilation studies show that the considerable effect on free volume related microstructure of the PVA due to doping and complex formation. These microstructural modifications are also enhances PVA crystallinity which is reflected from XRD studies. It is also observed that the TiO 2 particle forms cluster within the PVA due to the aggregation of particles and these particle cluster size increases with dopant concentration. These microstructural variations due to doping affects the DC electrical conductivity and its variations are understood based on the intra chain one-dimensional interpolaron hopping conduction mechanism. POLYM. COMPOS., 37:987-997, 2016.

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The effect of salt (LiClO 4 ) on free volume-related microstructural, optical, and dielectric properties of lithium perchlorate (LiClO 4 )-doped sodium alginate (NaC 6 H 7 O 6 ) 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 LiClO 4 interact with the OAH 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 s 3, as an indication of local electron density and mean free volume radius. The o-Ps pickup intensity I 3 , reflects the probability of o-Ps formation. The o-Ps components s 3 and I 3 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.