High molecular weight and sulfoaromatic carboxylic acid salt-terminated telechelic ionomeric polyester.

A telechelic ionomeric polyester is prepd. by reacting a first diol with a sulfoarom. carboxylic acid salt to form a sulfoarom. carboxylate ester salt, and polymg. it with a diester and a second diol in the presence of a transesterification catalyst. 1,4-Butane diol 50.440 g, 3-sulfobenzoic acid sodium salt 2.686 g and titanium tetrabutoxide 109 mg were stirred at 230° for 1 h, followed by addn. of di-Me terephthalate 77.624 g and the mixt. was reacted at 215° for 2 h and then at 245° with a dynamic vacuum was applied for 100 min to give PBT with Mw 45,800, ionic content 2.8%, sulfonated end-groups/total end-groups 0.85