Abstract The polyesterification reaction of maleic anhydride and 1,4‐butylene glycol was carried out, using p ‐toluensulphonic acid as catalyst. The resulting material was characterized by IR and H 1 ‐NMR spectroscopy, end group analysis, and gel permeation chromatography. It is shown that there is a relationship between maleate to fumarate isomerization and steric interaction among condensed groups on the one hand and the tendency of the reacting system to crosslink or gel.
