Alkylsulfonioarylene and thioarylene polymers derived from sulfonium electrophiles

Superacidification of sulfoxides and sulfinates effects the electrophilic substitution reaction of the resulting hydroxysulfonium ions onto aromatic rings with the elimination of H₂O at room temperature. The present account emphasizes the utility of the reaction for use as an elementary step in organic synthesis. The product, the alkyldiarylsulfonium ion, often quantitatively obtained, allows the synthesis of alkylsulfonio-bridged (λ⁴-alkylsulfanyliumdiyl) aromatic polymers. High molecular-weight poly(alkylsulfonioarylene) salts with a wide range of structural dimensionalities from linear to network architectures have been made accessible by the regioselective condensation of aryl sulfoxides. The polymers possess interesting properties such as good solubility in polar organic solvents and sometimes even in H₂O, susceptibility to nucleophiles to provide thioarylene derivatives, photo-degradability, and electric semiconductivity, according to the dimensionality of the molecule. The synthetic chemistry of the alkylsulfonioarylene polymers as well as their possible applications in high molecular-weight poly(thioarylene) synthesis, photochemical recycling processes of an engineering plastic poly(thio-1,4-phenylene), and photo-resist technologies, are reviewed.