Polymer-supported sulfonimide as a novel water-tolerant Brønsted acid catalyst for esterification of equimolar carboxylic acids and alcohols

A novel polymer-supported sulfonimide (PS-SI), 10-(4′-perfluorobutylsulfonamino sulfonylphenyl)decylpolystyrene, was synthesized and characterized by FT-IR, solid state 19F NMR, SEM and TGA. The acid strength determination indicated that PS-SI was a strongly acidic polymer. The catalytic performance of the polymer catalyst was tested by direct esterification of equimolar carboxylic acids and alcohols in excess water. The results showed that PS-SI was an effective Brønsted-acid catalyst and could be reused several times without any loss of catalytic activity.