| Abstract
| - Polybutadiene samples of different molecular weight have been synthesized by anionicpolymerization as initiated by sec-butyllithium with low polydispersity and a major content of 1,2-vinylunits. They have been analyzed by time-of-flight secondary ion mass spectrometry (ToF-SIMS) in orderto investigate the sensitivity of this method toward the sec-butyl end group and toward the molecularweight. The SIMS spectra show the characteristic fragment of the end group, C4H9+ at m/z = 57, whosethe peak intensity is strongly dependent on the polymer molecular weight, as is the case for almost allthe fragment intensities. A model consistent with the peak intensity variations is used to give some newinsights into the fragmentation mechanism at the end groups and within the main chain. Moreover, theanalysis of the end group fragment allows Mn to be readily determined up to Mn = 4 × 104 from, forexample, the Y(53)/Y(57) intensity ratio where Y(53) is the intensity of the deprotonated repeat unit ([M −H]+). Other Mn calibration methods have also been used and are discussed in terms of their accuracyand physical meaning.
|
