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

New polyimides have been prepared from 2,2'-bis(fluoroalkoxy)benzidines and several dianhydrides. The new diamines, with fluoroalkoxy groups OCF3, OCF2CF2H, and OCF2CFHOC3F7, were obtained from the corresponding 3-(fluoroalkoxy)nitrobenzenes by reduction to hydrazo derivatives, followed by benzidine rearrangements. High-quality polyimide films from these diamines have been prepared by standard procedures and their thermal, mechanical, and electrical properties compared to known polyimides, including those derived from 2,2'-bis(trifluoromethyl)benzidine. Polymers from the diamine with OCF3 substituents show an especially favorable combination of low dielectric constant, moisture absorption, and coefficient of thermal expansion (CTE) and high thermal stability, suggesting promise as a next-generation material for electronics applications. Polymers from diamines with the largest fluoroalkoxy substitutents have very low moisture absorption, but surprisingly high CTE.