A new aromatic polyether, poly(2-phenylphenylene oxide) with no C––O structures was synthesized by regioselective oxidative polymerization of 2-phenylphenol with an artificial enzyme catalyst. The polymerization produced the C–O coupling polymer completely without C––O structures, which occurred from oxygenation as well as C–C coupling with conventional catalysts. The polymer had a broad molecular weight distribution because of including bending and branching structures, although consisting mainly of linear units. After reprecipitation to increase the molecular weight, the resulting polymer showed not only high thermal stability exceeding 500 ◦C but also an extremely low dielectric constant of 2.22 @ 10 GHz as fully aromatic hydrocarbontype polymers. Even without sp3-carbon nor fluorine atoms to reduce dielectric constants, the very low value would be caused by the asymmetrical 2-phenyl substituent in the repeating unit and the bending and branching structures in the polymer chain.
