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ToF‐SIMS and computation analysis: Fragmentation mechanisms of polystyrene, polystyrene‐d 5 , and polypentafluorostyrene
Author(s) -
Ng KaiMo,
Lau YiuTing R.,
Weng LuTao,
Yeung KingLun,
Chan ChiMing
Publication year - 2018
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.6361
Subject(s) - chemistry , polystyrene , fragmentation (computing) , ion , mass spectrum , polyatomic ion , electronegativity , electron ionization , mass spectrometry , analytical chemistry (journal) , organic chemistry , ionization , polymer , chromatography , computer science , operating system
We studied the time‐of‐flight secondary ion mass spectrometry fragmentation mechanisms of polystyrenes—phenyl‐fluorinated polystyrene (5FPS), phenyl‐deuterated polystyrene (5DPS), and hydrogenated polystyrene (PS). From the positive ion spectra of 5FPS, we identified some characteristic molecular ion structures with isomeric geometries such as benzylic, benzocyclobutene, benzocyclopentene, cyclopentane, and tropylium systems. These structures were evaluated by the B3LYP‐D/jun‐cc‐pVDZ computation method. The intensities of the C 7 H 2 F 5 + (m/z = 181), CyPent‐C 9 H 3 F 4 + (m/z = 187), CyPent‐C 9 H 4 F 5 + (m/z = 207), and CyPent‐C 9 H 2 F 5 + (m/z = 205) ions were enhanced by resonance stabilization. The positive fluorinated ions from 5FPS tended to rearrange and produce fewer fluorine‐containing molecular ions through the loss of F (m/z = 19), CF (m/z = 31), and CF 2 (m/z = 50) ion fragments. Consequently, the fluorine‐containing polycyclic aromatic ions had much lower intensities than their hydrocarbon counterparts. We propose the fragmentation mechanisms for the formation of C 5 H 5 + , C 6 H 5 + , and C 7 H 7 + ion fragments, substantiated with detailed analyses of the negative ion spectra. These ions were created through elimination of a pentafluoro‐phenyl anion (C 6 F 5 − ) and H + , followed by a 1‐electron‐transfer process and then cyclization of the newly generated polyene with carbon‐carbon bond formation. The pendant groups with elements of different electronegativities exerted strong influences on the intensities and fragmentation processes of their corresponding ions.