Direct Evidence of Positron Trapping at Polar Groups in A Polymer-Blend System

Energy spectra of positron annihilation radiation were measured in polymer blends of polyethylene and ethylene vinyl acetate copolymer (E/VA) by means of the coincidence Doppler broadening technique. Positron annihilation with the core electrons of oxygen was appreciably increased by the addition of small amounts of E/VA to polyethylene and was detected with a sensitivity one order of magnitude higher than would be expected from the number density of the oxygen atoms in the polymer blends.