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| - Time-of-Flight Secondary Ion Mass SpectrometricAnalysis of Polymer Tertiary Structure in LangmuirMonolayer Films of Poly(dimethylsiloxane)
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| - A series of model systems of poly(dimethylsiloxane)(PDMS) of molecular mass 2400 Da and low polydispersity (1.09) were prepared using the Langmuir−Blodgetttechnique to investigate the effects of tertiary structure onthe ion formation probability in time-of-flight secondaryion mass spectrometry (TOF-SIMS). Using data from themeasured surface pressure−area isotherm for PDMSordered monolayer, films were transferred to silver mirrorsubstrates from the various regions in the isotherm wherestructural changes are observed. Two particular conformations of the polymer are examined here: a linearcaterpillar-like structure and a coiled helical structure.Reflection absorption Fourier transform infrared spectroscopic analysis indicates structural changes for the filmsrelated to adjustments to the orientation of the polymericbackbone consistent with the formation of two distinctstructures. The polymeric changes translate into differences in ion formation probability of fragments in boththe low (<250 Da) and high (>1000 Da) mass range.Data are also presented to analyze how tertiary structuremay affect the apparent polydispersity index calculatedfrom the TOF-SIMS spectra.
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