Novel Approach to Ladder-Type Polymers: Polydithiathianthrene via the Intramolecular Acid-Induced Cyclization of Methylsulfinyl-Substituted Poly(meta-phenylene sulfide)

The acid-induced intramolecular cyclization reaction of aromatic methylsulfinyls has proven to be a suitable synthetic tool for the preparation of ladder-type oligomers and polymers on the basis of thianthrene (= “9,10-dithiaanthracene”). This approach allows for the synthesis of tetrathiapentacene oligomers in high yields. The concept was transferred to a polymer-analogous reaction of a methylsulfinyl substituted poly(meta-phenylene sulfide) precursor, which under strongly acidic conditions and following demethylation gave a double-stranded poly(phenylene sulfide), known as polydithiathianthrene. Although the resulting ribbon is not defect-free, the high degree of cyclization via this novel technique has been demonstrated by detailed spectroscopic and spectrometric studies.