Synthesis and Characterization of Soluble Low-κ Poly (aryl ether ketone) Copolymers with Pendent Adamantyl Groups

The aromatic bisphenol monomers containing bulky pendant (adamantyl) groups, 4-(1-adamantyl)-1,3-benzene diol (AdRES) and 4,8-bis(1-adamantyl)-1,5-dihydroxy naphthalene (AdNp) were successfully prepared via the Friedel—Crafts reaction and used to synthesize a series of new poly (aryl ether ketone) copolymers with (3-trifluoromethyl) phenyl hydroquinone or other bisphenols and 4,4′-difluorobenzophenone (DFB) by nucleophilic aromatic substitution polycondensation. All the novel PAEKs were amorphous and their solubility was improved by the introduction of bulky pendant groups, so they were readily soluble in common organic solvents. DSC data showed that T g values of the resultant copolymers were dramatically increased when adamantane is incorporated into the copolymers as a pendent group and their T g values increased with increasing content of adamantyl groups. According to thermogravimetric analysis, all the polymers showed excellent thermal stabilities. The mechanical properties of the polymers can be controlled by varying the molar ratio of diphenol-containing adamantyl to (3-trifluoromethyl) phenyl hydroquinone. These novel poly (aryl ether ketone) films had low dielectric constants ranged from 2.62 to 2.95 at 1 MHz and low water absorptions of 0.12—0.29%; their dielectric constants decreased with the increasing content of the adamantyl group.