Ionic conductivity and free volume related microstructural properties of LiClO4/PVA/NaAlg polymer composites: Positron annihilation spectroscopic studies

• Published in: Journal of non-crystalline solids 2016-12, Vol.454, p.19-30
• Main Authors: Sheela, T., Bhajantri, R.F., Nambissan, P.M.G., Ravindrachary, V., Lobo, Blaise, Naik, Jagadish, Rathod, Sunil G.
• Format: Article
• Language: English
• Subjects: Calorimetry; Conductivity; Decomposition; Doping; Formations; Free Volume; Ionic conductivity; Mechanical properties; Poly(vinyl alcohol); Polymer matrix composites; Positron annihilation; Positronium; Sodium Alginate; Thermal properties
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2016.10.010

Poly(vinyl alcohol) (PVA)/sodium alginate (NaAlg) polymer composites were prepared by doping with lithium perchlorate salt (LiClO4) using solution casting method. The miscibility, crystallinity, conductivity, thermal behavior, mechanical strength and free volume properties have been examined. The FTIR results reveal that the dopant (Li+) ions interact strongly with polymer chains through hydrogen bonding. X-ray diffraction patterns show a variation in the degree of crystallinity with increase in LiClO4 concentration. The dc conductivity increases with addition of LiClO4 salt concentration at room temperature and is attributed to increase in the number of mobile charge carriers (Li+ and ClO4−) and degree of dissociation of salt in the composites. The variations in the mechanical properties are observed upon doping. The differential scanning calorimetric (DSC) study shows a single glass transition temperature (Tg) and reveals the compatibility and variation in the decomposition temperature (Td). Thermogravimetric analyses (TGA) shows a decrease in the decomposition temperature with addition of lithium salt concentration. The positron annihilation lifetime spectroscopy (PALS) and Doppler broadening measurements were carried out for all the samples in terms of positron annihilation and positronium formation. The S-parameter shows a similar behavior as that of the o-Ps lifetime and o-Ps intensity. The correlation between carrier concentration and ionic conductivity with Ps formation was observed in this particular system. The conductivity versus temperature plot was found to follow an Arrhenius nature. •LiClO4 salt doped PVA/NaAlg composites were prepared.•PALS and DBS results were correlated with other results.•The increase in crystallinity is due ordering in the molecular structure.•Highest ionic conductivity of 1.83×10−4S/cm is observed.•The composites shown good mechanical strength and thermal stability.