TOF-SIMS/MALDI-TOF combination for the molecular weight depth profiling of polymeric bilayer

摘要

A polymeric bilayer composed of two poly(styrene) layers differing by their molecular weights (MW) was elaborated to mimic a MW gradient and analyzed by a combination of TOF-SIMS, MALDI-MS and Nanoscratch (NS). A direct TOF-SIMS profiling conducted using a Cs~+ ion beam lead to the detection of fragments from carbonated layers without any data about their MW, making the fine bilayer architecture indistinguishable. Spots of various depths were hence created using the same Cs+ ion bombardment for different sputtering times, and further mass-analyzed by the recently developed Surface-Layer MALDI-MS technique, to evaluate the MW of the very top polymeric layer of each crater. The off-line combination of ion etching and LASER analysis allowed a molecular weight depth profile to be plotted, as a function of the physical depth measured by NS in each crater (instead of the usual sputter time). This original coupling is expected to provide useful molecular and/or molecular weight data about complex organic and/or polymeric multi-layers or gradients.