The use of positron annihilation lifetime technique to study the effect ofdoping metal salts on polyhydroxamic acid polymers

Polyhydroxamic acid (PHA) from polymethacrylamide (PMAA) was prepared. Chro mium chloride (CrCl3) and ferric chloride (FeCl3) salts were added to the p olymer in order to increase its electrical conductivity, i.e., the dopants help produce semiconducting properties. The positron annihilation lifetime technique spectroscopy (PALS) was used to study the changes in the free vol ume as a function of FeCl3 and CrCl3 concentrations. ortho-Positronium life time components were used to estimate the free volume parameters. It was fo und that the hole size and the total free volume fraction decreased with Fe Cl3 concentration. On the other hand, the hole size increased slightly with CrCl3 concentration and then decreased, while the total free volume fracti on increased continuously. The free volume distributions were determined fr om ortho-positronium distributions. The electric conductivity as a function of FeCl3 and CrCl3 concentrations showed fluctuation behavior and showed a continuous increase with the increase in temperature. The correlation betw een positron annihilation parameters and electric conductivity were discuss ed. (C) 2001 John Wiley & Sons, Inc.