Information on the Monomer Sequence of Poly(lactic acid) and Random Copolymers of Lactic Acid and Glycolic Acid by Examination of Static Secondary Ion Mass Spectrometry Ion Intensities

Static secondary ion mass spectrometry (SSIMS) has been used to analyze a range of poly(lactic acid)s (PLA) and copolymers of lactic and glycolic acids (PLGA). Ion assignments for the full range of radical cations observed are presented, along with the observation of chain end contribution to the SSIMS spectra in the case of low molecular weight PLA. The ion intensities within different radical cation series in PLGA have been compared with theoretical intensity distributions. In the case of random copolymers, the radical cation intensities are almost identical with the predicted binomial distribution. Dimeric character in some of the polymers is demonstrated using a statistical approach.