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Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
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Gas-phase conformations of cationized poly(styrene) oligomers
Jennifer Gidden1, Michael T Bowers, Anthony T Jackson
1Department of Chemistry and Biochemistry, University of California, Santa Barbara 93106, USA.
Summary
Metal cations like Li+, Na+, Cu+, and Ag+ form quasi-linear structures with poly(styrene) oligomers, influencing their conformations and fragmentation. These findings aid in understanding cationized polymer behavior.
Area of Science:
- Polymer Chemistry
- Physical Chemistry
- Mass Spectrometry
Background:
- Understanding the gas-phase conformations of cationized polymers is crucial for interpreting mass spectrometry data.
- Poly(styrene) oligomers are model systems for studying polymer behavior.
Purpose of the Study:
- To investigate the gas-phase conformations of poly(styrene) oligomers (PSn) cationized by various metal ions (M+).
- To correlate experimental ion mobility data with molecular modeling results.
- To elucidate the influence of metal cationization on polymer structure and fragmentation.
Main Methods:
- Ion mobility experiments were used to measure collision cross-sections of M+PSn ions.
- Matrix-assisted laser desorption/ionization (MALDI) was employed for ion formation.
- Molecular mechanics and dynamics calculations were performed to model conformations and energies.
Main Results:
- Experimental collision cross-sections for M+PSn were similar across Li+, Na+, Cu+, and Ag+ and increased linearly with oligomer length (n).
- Molecular modeling revealed quasi-linear structures with metal cations sandwiched between phenyl groups, particularly stable near the oligomer's middle.
- Calculated cross-sections showed good agreement (1-2% deviation) with experimental values.
- Metal cations induced alignment of phenyl groups, contrasting with random orientations in neutral poly(styrene).
Conclusions:
- The study provides insights into the gas-phase structures of cationized poly(styrene) oligomers.
- Conformational preferences are influenced by metal cation binding, affecting polymer backbone and side-group arrangements.
- These findings contribute to understanding fragmentation mechanisms in techniques like collision-induced dissociation (CID).
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