Polyaryl ethers (PAEs) are high-performance thermoplastics composed of an ether-linked aromatic backbone. This class of material exhibits high thermal stability, chemical resistance, fire resistance, high mechanical strength, and good processability. Historically, much attention has been given to 1,1,1,3,3,3-hexafluoroisopropylidene (HFIP) derivates due to the increased solubility, thermal stability, and glass transition, imparted by the -CF<sub>3</sub> groups. A good example of the HFIP improvements is the imminent industrial application of bisphenol AF. Semi-fluorinated PAEs of this kind are typically synthesized from halogenated bis-aryl monomers via nucleophilic aromatic substitution with the corresponding bis-phenoxide, which implies several synthetic steps. A less explored alternative is the electrophilic aromatic substitution (EAS) of aryl ethers to produce novel semi-fluorinated analogs. Herein, a practical and direct synthesis of semi-fluorinated PAE is presented via Friedel-Crafts polymerization of hexafluoroacetone trihydrate and diphenyl ether, catalyzed by triflic anhydride. Although prepared by indirect methods in 1966 (Stamatoff et al., US Patent 3,291,777) further pursuits and modern characterizations surprisingly have not been reported. This Polymer represents one of the most simple and obvious semi-fluorinated PAEs, yet it has remained unexplored for years. The methodology presented herein was applied to other aromatics monomers such as dibenzofuran and biphenyl. The polymeric materials were characterized by NMR, FTIR, GPC, XRD, TGA, and DSC. Results showed a successful polymerization with a low branching process depending on the temperature, thermal stability until 500 degrees Celsius under nitrogen, a glass transition (T<sub>g</sub>) around 170 degrees Celsius, and molecular weights ranging between 57-60 kDa. Finally, as its possible application, the optical and dielectric properties of these materials were studied.

Synthesis and characterization of polyaryl ethers containing hexafluoroisopropylidene enchainment via direct Friedel-Crafts polymerization of diaryl ethers and hxafluoroacetone hydrate

ACS Fall 2021

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