Abstract The polycondensation reaction between maleic anhydride and 1,6‐hexanediol, with p ‐toluenesulfonic acid as catalyst has been carried out. The product has been analyzed spectroscopically and the molecular weight determined by endgroup analysis and gel permeation chromatography. The influence of spatial interactions between condensed groups on the isomerization of maleate into fumarate is discussed, as well as the effects of even‐ and odd‐ numbered carbon atom glycols. © 1993 John Wiley & Sons, Inc.