Structural characterization of multicomponent copolyesters by mass spectrometry

The structural characterization and composition of five random copolyesters , originating from 1,4-butanediol and mixtures of succinic, adipic, sebacic , and terephthalic acids, were obtained by analysis of their fast atom bomb ardment (FAB) and their matrix-assisted laser desorption ionization (MALDI) mass spectra. Multicomponent condensation copolymers may sometimes prove d ifficult to characterize by conventional techniques, whereas mass spectrome try is able to handle them. Once the choice between Bernoullian or Markoffi an models has been made, the determination of copolymer composition, number -average sequence length, and related quantities can be achieved by applyin g well-defined analytical equations. The theoretical mass spectra of multic omponent copolymers are remarkably simple, and the number of peaks appearin g in each copolymer mass spectrum is easily predictable. Different kinds of spectral fitting algorithms may help in the actual computations, and it ha s been shown that the apparent complexity of mass spectra of copolymers is due to the presence of mass series bearing different end groups. By selecti ng a single mass series, one obtains an experimental spectrum immediately c omparable to the theoretical one. Detailed examples, together with a discus sion on the reliability of results, are given to apply the computation proc edures and to gain proper understanding of the concepts involved.