SynopsisThis paper describes the effect of metal halides (Co2+, Sn2 +, and Hg2+) on the properties of polyimides. Low temperature, solution polycondensation reaction of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether was used for preparation of a poly(amide-acid) solution in dimethylformamide ([q] = 2.0 dL/g). Films containing 1% (w/w) of cobalt (11) chloride, tin (11) chloride, and mercury (11) chloride were prepared by solution casting of poly(amide-acid) from the DMF solution. Cyclodehydration to polyimide was done by heating the films in nitrogen atmosphere for one hour each a t loo", 200", and 250°C. The color of the films depended on the dopant and was yellow (HgCI, or SnC1,) or green (CoC1,). Higher percentage weight loss was observed in doped films in nitrogen atmosphere in the temperature range of 250-400°C. No significant difference in thermal behavior of doped and undoped films was observed above 500°C. Doping reduced the tensile strength of polyimide films, maximum reduction was observed in CoC1,-doped film. The electrical conductivity of polyimide films as a function of temperature and field was studied. Undoped polyimide showed ohmic behavior up to 150°C. In doped films at lower voltages Poole-Frenkel mechanism was operative, while at high voltages Richardson-Schottky's mechanism was operative. Dielectric relaxation in polyimide films was also studied.