Organosoluble and optically transparent fluorine-containing polyimides based on 4,4′-bis(4-amino-2-trifluoromethylphenoxy)-3,3′,5,5′-tetramethylbiphenyl

A novel fluorinated diamine monomer, 4,4′-bis(4-amino-2-trifluoromethylphenoxy)-3,3′,5,5′-tetramethylbiphenyl, was prepared by a nucleophilic chloro-displacement reaction of 3,3′,5,5′-tetramethyl-4,4′-biphenol with 2-chloro-5-nitrobenzotrifluoride and subsequent reduction of the intermediate dinitro compound. The diamine was reacted with aromatic dianhydrides to form polyimides via a two-step polycondensation method; formation of poly(amic acid)s, followed by thermal imidization. All the resulting polyimides were readily soluble in many organic solvents and exhibited excellent film forming ability. The polyimides exhibited high Tg (312–351 °C), good thermal stability, and good mechanical properties. Low moisture absorptions (0.2–1.1 wt%), low dielectric constants (2.54–3.64 at 10 kHz), and low color intensity were also observed.