Effect of barium chloride doping on PVA microstructure : positron annihilation study

• Published in: Applied physics. A, Materials science & processing Vol. 87; no. 4; pp. 797 - 805
• Main Authors: BHAJANTRI, R. F, RAVINDRACHARY, V, HARISHA, A, RANGANATHAIAH, C, KUMARASWAMY, G. N
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01-06-2007; Springer Nature B.V
• Subjects: Applied physics; Barium chloride; Chemical bonds; Chemical reactions; Complex formation; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystal structure; Crystallinity; Dielectric properties; Dopants; Doping; Exact sciences and technology; Hydrogen bonding; Materials science; Microstructure; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Phase separation; Physics; Polymer films; Polymers; Polyvinyl alcohol; Positron annihilation; Room temperature; Crystalline phase; Electrical conductivity; Impurity density; Dielectric properties; Impurity cluster; Doping; Positron annihilation; Crystallinity; XRD; Phase separation; PVA; Microstructure; IV characteristic
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-007-3923-y

Microstructural studies on BaCl2 doped polyvinyl alcohol (PVA) polymer films were carried out using density, PAL and dielectric measurements at room temperature. The positron annihilation studies on these samples shows considerable effect on the PVA microstructure due to doping and is understood by invoking the chemical reaction between Ba2+ ions of BaCl2 with OH groups of PVA via intra/inter molecular hydrogen bonding, which forms the complex. This complex formation modifies the free volume content in the amorphous fraction, and results in an enhancement of the polymer crystallinity. At higher dopant concentrations, the number of such complexes increases, and ends up with the formation of dopant aggregates or agglomerates leading to certain phase separation into a polymer-rich phase and a dopant-rich phase. These phase separations are thought to be due to the existence of two or more crystalline phases within the polymer matrix. The XRD study also supports this enhancement of PVA crystallinity due to doping. The electrical studies on the doped PVA reflects that the complex formation due to doping affects the microstructure and hence the dielectric properties including the dc and ac conductivities of the polymer. All of these observed results were analyzed and understood based on the microstructural modification of PVA as a function of dopant concentrations.