Synthesis and characterization of sulphonated PEES copolymers by NMR spectroscopy

Two sulphonated PEES copolymers were synthesized by reacting 75 or 60 mol% silylated hydroquinone sulphonic acid and 25 or 40 mol% of hydroquinone with 4,4′-difluorodiphenyl sulphone. The number average molecular weights determined by GPC were 13.250 and 12.050 g/mol. In the FTIR spectra, in addition to the characteristic absorption bands due to aromatic skeleton, absorption bands associated with sulphonic acid groups were observed at ∼3500, 1172, 1080, 1026, and 706 cm−1. In 1H NMR, the aromatic proton resonance signals were observed between δ = 6.99 and 7.96 ppm. 13C{1H} NMR spectra of these copolymers were complex and in order to resolve this, two-dimensional (2D) NMR techniques were utilized. Heteronuclear single quantum coherence (HSQC), total correlated spectroscopy (TOCSY), and heteronuclear multiple bond correlation (HMBC) were used for assigning the structure of the copolymers.