Characterization of polymer surfaces using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and atomic force microscopy (AFM)

Various polymer surfaces were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and atomic force microscopy (AFM) to obtain data on their structures and morphologies, to elucidate polymer properties. Polyisobutylenes and polyisoprenes were studied by static TOF-SIMS. Structural characteristics of polymers are correlated with peaks in the low mass (fingerprint) region of the spectra. Effects of branching and unsaturation in the polymer structure on ion formation were studied. The spectra consist of a sequence of repeating patterns in the high mass region. Each pattern contains a certain number of clusters. Two major radical fragmentation mechanisms, statistical main chain scission and initial loss of a methyl group, are discussed; other reaction mechanisms are also possible. It was found that multiple species with various degrees of unsaturation accounted for the configuration of each cluster. The data indicate that ion formation varies as a function of polymer molecular weight. Polymer molecular weight changes the cluster intensities and structures in a pattern. The AFM technique was used to examine the surface morphology of a microcapsule formed by polyelectrolyte complexation, under ambient conditions in a liquid environment. The capsules exhibited different morphologies and surface roughness depending on the composition of the cation solution. These quantitative results in return can be used as a feedback for the optimization of the capsule membrane. Surface characterization of polytetrafluoroethylene (PTFE) rubbed along a heated microscope slide was carried out by AFM. The images showed orderly structures of PTFE fibrils aligned in the mechanical deposition direction. Furthermore, finer structures like highly organized parallel chains, which could be assigned as individual molecules, were also revealed. it was possible to resolve the fine structure of individual -CF{dollar}sb2{dollar} groups by Fast Fourier Transform. TOF-SIMS and AFM were then combined to study thin films of iso-, syndio- and atactic polypropylenes deposited on gold and silver coated mica. The AFM images indicate that stereoregularity determines the polymer's surface orientation. The SIMS spectra also show various unique fragmentation pattern structures, which could possibly be due to the different tacticities of the polymers.