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Positron annihilation lifetime (PAL) and Doppler broadening (DB) measurements were carried out in four semicrystalline polymer samples, viz., polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polytetrafluoroethylene (PTFE), and Nylon 6, 6 (PA). A correlation between the S and Wparameters which reflect the electron momentum, and the orthc-positronium (0-Ps) lifetime reflecting the electron densities in free volume sites is observed. Interestingly, the present results support the known intuition that 0-Ps has a higher momentum component compared to p-Ps and free annihilations but different from that observed by Davies and Pethrick.') Manasagangotri, Mysore 570 006, India.1'

ABSTRACT:The influence of iodine on the free volume of acrylonitrile-butadiene-styrene (ABS) was investigated by positron annihilation lifetime spectroscopy (PALS). The results indicate the filling of free-volume holes, formation of a positronium-iodine compound (PsI 2 /PsI), and possible charge-transfer complexes (CTCs) in the initial stages and the swelling of iodine in the final stages of sorption. The present study also revealed that iodine acts as a chemical quencher of o-Ps. The average size of the free volume suggests that I 0 3 is the predominant species that fills up the free-volume holes during iodination. The diffusion process in the present case shows non-Fickian behavior and deviates from Fujita's free-volume concept as far as the fractional free volume and diffusion coefficient are concerned.