In PES2_NC sample, several congeners exist with variable DP of aliphatic acid (2) ranging from 0 to 4, with the aromatic DP being between 1 and 14 (3 and 4 cannot be distinguished from each other because they are isobaric). This situation changes significantly when analyzing PES2_LCC sample. In this case, the species detected in the same molecular weight range are deprived of aliphatic acid (2). In particular, the assigned monoacid terminated chains of PES2_LCC sample carry 0 to 1 aliphatic monomer and the intensities of the signals are below 10%. In contrast, the di-acid terminated chains were detected with a maximum of two aliphatic units and an intensity of 2% maximum.