Studies of polyisobutylene using time-of-flight secondary ion mass spectrometry (TOF-SIMS)

Abstract

A series of polyisobutylenes (PIBs) with average molecular weights from 800 to 4 × 10 5 were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The PIB spectra consist of a sequence of repeating patterns. Four clusters are observed within each pattern. Each cluster corresponds to several species, which are neutral fragments generated from polymer chain scission, cationized by a silver ion. The species formed have various numbers of double bonds and/or rings, and are separated by two mass units. The data indicate that the average molecular weight of PIB affects the ion formation. It changes the relative cluster intensities in a pattern, and also varies the cluster structures. More fragment-ion species can be detected from a high molecular weight polymer, and the unsaturated fragments are predominant. In addition to the large fragments, small fragment ions also provide information about some structurally important features.