13C NMR characterization of branched structures in polyesters resulting from the reaction of maleic and phthalic anhydride with 1,2‐propanediol

Several model compounds were synthesized in order to study the side reactions taking place during the synthesis of polyesters, especially chain branching due to the addition of hydroxyl groups to maleate or fumarate double bonds. Diesters or polyesters from 1,2‐propanediol with fumaric acid and various dialkyl alkoxysuccinates were used as models. Their synthesis and characterization are described. The interpretation of their 13C NMR spectra is reported. These spectra are compared with those of the diesters and polyesters of phthalic acid previously described and with the spectrum of a commercial unsaturated polyester. It was possible to identify and to assign the various end groups and the structures resulting from chain branching.