SYNTHESIS AND PROPERTIES OF FLUORINATED POLYIMIDES FROM NOVEL 2,2'-BIS(FLUOROALKOXY)BENZIDINES

New polyimides have been prepared from 2,2'-bis(fluoroalkoxy)benzidine s and several dianhydrides. The new diamines, with fluoroalkoxy groups OCF3, OCF2CF2H, and OCF2CFHOC3F7, were obtained from the correspondin g 3-(fluoroalkoxy)nitrobenzenes by reduction to hydrazo derivatives, f ollowed by benzidine rearrangements. High-quality polyimide films from these diamines have been prepared by standard procedures and their th ermal, mechanical, and electrical properties compared to known polyimi des, including those derived from 2,2'-bis(trifluoromethyl)benzidine. Polymers from the diamine with OCF3 substituents show an especially fa vorable combination of low dielectric constant, moisture absorption, a nd coefficient of thermal expansion (CTE) and high thermal stability, suggesting promise as a next-generation material for electronics appli cations. Polymers from diamines with the largest fluoroalkoxy substitu tents have very low moisture absorption, but surprisingly high CTE.