Improved Synthesis of Oligomeric Sulfone‐Based Phthalonitriles

An improved method has been developed to produce an oligomeric sulfonyl‐containing phthalo­nitrile with better processability. The oligomeric phthalonitrile monomer is prepared from the reaction of an excess amount of bisphenol A with 4‐(chlorophenyl)sulfone in the presence of a mixed base system (NaOH/K2CO3) in a dimethylsulfoxide/toluene solvent mixture, followed by end‐capping with 4‐nitrophthalonitrile in a two‐step, one‐pot reaction. This phthalonitrile resin exhibits lower viscosities than previously reported systems for molding into various shapes. After being thermally cured to yield crosslinked polymers, this sulfonyl‐based polymer demonstrates superb mechanical properties and thermo‐oxidative stability, absorbs less than 1.0 weight percent water, and maintains good dielectric properties. image