Iodine-doped polyvinylalcohol using positron annihilation spectroscopy

Lobo, B. and Ranganath, M. R. and Chandran, T. S. G. R. and Rao, G. V. and Ravindrachary, V. and Gopal, S. (1999) Iodine-doped polyvinylalcohol using positron annihilation spectroscopy. PHYSICAL REVIEW B, 59 (21). pp. 13693-13698.

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Iodine-doped polyvinylalcohol, doped up to 52 wt %, was studied using positron annihilation lifetime technique and Doppler broadening of annihilation radiation. Three component, free fit analysis was used for the lifetime spectra. It is found that I-3 drops sharply on initial iodine doping, whereas decrease in tau(3) is small, indicating inhibition of positronium formation by the dopant. The S parameter, on iodine doping, initially shows a drastic increase due to the decrease in crystallinity of the doped sample. Differential scanning calorimetry (DSC) and x-ray diffraction curves confirm that doping results in decreased crystallinity of the sample. tau(3) increases beyond 23 wt% doping level due to structural changes induced by formation of polyiodide complexes, which is confirmed by UV-Vis spectra, for moderately and highly doped samples. The drop in tau(3) at higher levels of doping (>44 wt %) suggests chemical quenching of positronium, probably due to iodine aggregation. DSC confirms formation of iodine aggregates, as revealed by a large endotherm at 185 degrees C, for doping levels beyond 47 wt %. S0163-1829(99)08321-6].

Item Type: Article
Subjects: Physical Sciences > Physics
Divisions: PG Campuses > Manasagangotri, Mysore > Physics
Depositing User: Users 13 not found.
Date Deposited: 19 Apr 2013 09:50
Last Modified: 31 Aug 2013 11:09

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