Meisenheimer Complex Inspired Catalyst- and Solvent-Free Synthesis of Noncyclic Poly(aryl ether sulfone)s

Abstract

Identifying solvent- and catalyst-free conditions for polymerizations of engineering thermoplastics is of increasing interest due to new polymer processing technologies such as 3-D printing. We report the selective formation of linear poly(aryl ether sulfone)s (PESs) from the polycondensation of trimethylsilyl-protected bisphenol A (TMS-BPA) with nitro-substituted diaryl fluorides without added solvent or catalyst. DFT calculations show that nitro groups strategically placed in the ortho-position to the fluoride leaving group form a stable Meisenheimer complex during polyether synthesis. This strategy represents a route to linear PESs that employs anionic conditions, destabilizing propagating phenoxide chain ends preventing backbiting while simultaneously stabilizing the Meisenheimer complex intermediate. Thermodynamic over kinetic control in the polycondensation minimizes cyclic PES formation and promotes the formation of pure linear PESs.