Project No: 16300314
Title: Understanding of ToF-SIMS Fragmentation Processes Through The Establishment of a Clear Relationship Between the Structures of the Secondary Ions and Structures of the Polymers
PI: Prof. Yeung, King Lun
CI: Prof. Chan, Chak-Keung; Prof. Chan, Chi Ming; Dr. Ng, Kai Mo; Prof. Weng, Lu-Tao
Surface analysis is an indispensable tool in the field of materials science. Among all surface analysis techniques, Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is one of the most powerful one. The main advantage of ToF-SIMS is its rich molecular information and extreme high surface sensitivity. However, up until now, the ion formation mechanisms in a ToF-SIMS process are still not fully established. The reconstruction of the fragmentation pathways by detailed analyses of the structures of the fragment ions is the first step in the interpretation of ToF-SIMS spectra. The fragmentation process of a polymer is undoubtedly related to its polymer chain structure. A detailed investigation of the relationship between the structures of the secondary ions and the polymer chain structures should reveal interesting hints about the fragmentation mechanisms in SIMS processes. The objective of the proposed research is to systematically explore correlations between fragment ions and polymer chain structures. The proposed work will provide significant insight into the understanding of the fragmentation processes of ToF-SIMS. In this study, both homopolymers and copolymers with well defined structures will be selected. Two series of such polymers will be chosen. It is anticipated that a detailed comparison between the ToF-SIMS spectra obtained from these polymers would provide important clues to the formation mechanisms. The first series includes polystyrene (PS), poly (2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), PS with deuterium in the backbone [polystyreneD3 (PS-D3)] or in the pendant groups [polystyrene-D5 (PS-D5)]. The second series of polymers includes 6FBA-C4, 6FBA-C4-D8 and BA-C4, which are composed of a bisphenol hard segment and an aliphatic soft segment with fluorine, deuterium and hydrogen at defined positions. 6FBAC4 and BA-C4 will be synthesized by phase-transfer catalyzed polyetherification of 1,ndibromobutane with 4,4’-(hexafluoroisopropylidene)diphenol (6FBA) and bisphenol A (BA), respectively. 6FBA-C4-D8 polymer will be prepared by polycondensation of hexafluorobisphenol-A and the pre-dueterated 1,4-dibromo-butane-D8. A comparison between the ions of PS, PS-3D and PS-5D with those of 5FPS is of great interest due to the strong electronegativity of the fluorine atoms attached to the aromatic-ring. The second series of polymers is an ideal candidate for the study of the relationship between the structure of the ions and the structure of the polymers. The structure and intensity of the ions of 6FBA-C4, 6FBA-C4-D8 and BA-C4 will be thoroughly analyzed to determine if there are exchanges between hydrogen, fluorine and deuterium. This information will allow us to propose fragmentation mechanisms of the ions.