Effect of Structural Features and Humidity on the Dielectric Constant of Polyimides

Abstract

A series of aromatic polyimides and partially fluorinated aromatic polyimides were prepared and investigated to determine the structural features affecting their moisture absorption, dielectric constant, and dielectric constant as a function of relative humidity. The moisture absorption of polyimides is related to the total imide content of the polymer. Polyimides with a lower weight per cent of imide have a lower moisture absorption. Both dielectric constant and moisture absorption of polyimides can be reduced by incorporation of fluorine into the polymer. However, a minimum in moisture absorption (about 0.7 wt.%) and dielectric constant (about 2.7) is approached at about 20% fluorine by weight of the polymer.