Synthesis of new fluorene-based poly(aryl ether) containing pendant tert-butyl groups for low dielectric materials

A new fluorene-based bisphenol monomer containing pendant tert-butyl groups, 9,9-bis(3-tert-butyl-4-hydroxy)phenyl-fluorene (BTHF), was readily synthesized in high yield by a one-step reaction from inexpensive starting materials. The resulting poly(aryl ether) (FPAE 3) was successfully prepared by a mild nucleophilic aromatic substitution reaction using this fluorene-based bisphenol and decafluorobiphenyl. The obtained poly(aryl ether) exhibited good solubility in some low-boiling-point solvents and could be cast into flexible and strong film. It displayed high thermal stability with glass transition temperature at 264 °C and 5 % weight loss temperatures at 487 °C in air atmospheres. Moreover, it revealed low dielectric constants with the value of 2.64 at 1 MHz measured for its capacitance.