Improved synthesis and properties of aryl ether-based oligomeric phthalonitrile resins and polymers

Abstract

A versatile scheme to produce a multiple aromatic ether-linked phthalonitrile has been developed and applied to the preparation of two unique resin systems. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A or bisphenol A6F with 1,3-dibromobenzene in the presence of K2CO3 as the base in a N,N-dimethylformamide/toluene solvent mixture, followed by end-capping with 4-nitrophthalonitrile in a two-step, one-pot reaction. Both phthalonitrile resin systems exhibited excellent viscosities for molding various shaped articles and were thermally cured to yield crosslinked polymers. Each bisphenol-based polymer also demonstrated superb mechanical properties and thermo-oxidative stability while absorbing less than 1% percent water by weight. The two systems differed greatly in their relative reactivity toward the curing additive bis(4-[3-aminophenoxy]phenyl)-sulfone (m-BAPS). The presence of the electron withdrawing CF3 groups on the bisphenol A6F resulted in a faster curing reaction to the thermoset polymer but weaker mechanical properties and less overall thermal stability relative to the bisphenol A-containing resin. The bisphenol A6F polymer showed a lower overall water absorption but exhibited a comparable dielectric constant relative to the bisphenol A polymer.