Sulphonation of poly(phenylene ether sulphone)s containing hydroquinone residues

Analysis, mainly by n.m.r. spectroscopy, shows that when copolymers comprising phenylene-ether-phenylene-sulphone and phenylene-ether-phenylene-ether-phenylene-sulphone repeat units are dissolved in 98% sulphuric acid, the ether-phenylene-ether groups are monosulphonated completely, but the other phenylene groups remain unchanged. Thus, sulphonation of these copolymers in this way provides a simple technique for preparing poly(phenylene ether sulphone)s sulphonated to a predetermined extent. The solution viscosities, glass transition temperatures and water up-take of the sulphonated copolymers increase as the extent of sulphonation is increased.