HIGH-RESOLUTION TOF-SIMS STUDIES OF SUBSTITUTED POLYSTYRENES

High-resolution (M/DELTAM = 7000) time-of-flight secondary-ion mass spectrometry (TOF-SIMS) was used to study the mechanism of fragment-ion formation for several polystyrenes. Ions are formed from neutral fragments resulting from chain cleavage and are cationized with a silver ion. Spectra of the polystyrenes consist of repeating patterns of clusters of invidual peaks extending to m/z > 3000. Fragmentation of the polymer backbone can be explained by limited chain fragmentation, consistent with mechanisms proposed for other methods. Most polystyrenes show five clusters in their repeat pattern except for poly(alpha-methylstyrene) which differs considerably. This difference is discussed. Cluster structure can be explained by the contributing species having zero, one, or two rings and/or double bonds. The results of this study support the idea that chain fragmentation proceeds through a cyclic intermediate.