Author ORCID Identifier
Semester
Summer
Date of Graduation
2026
Document Type
Dissertation
Degree Type
PhD
College
Eberly College of Arts and Sciences
Department
Chemistry
Committee Member
Stephen J. Valentine
Committee Member
Brian V. Popp
Committee Member
Lisa A. Holland
Committee Member
David Ropartz
Abstract
The work presented in this dissertation was inspired by an analytical chemist’s arch-nemesis: contamination. When collision induced dissociation (CID) failed to produce any structurally informative fragment ions of a contaminant peak detected during the analysis of laminarin, charge transfer dissociation (CTD) paired with CID led to the identification of a cyclic dimer of nylon-6,6, which could then be linked back to a nylon filter during sample preparation. Before this practical test of CTD, CTD had successfully characterized the structures of a wide variety of biopolymers like peptides, lipids, and oligosaccharides, but the characterization of synthetic polymers by CTD had not been explored. This work therefore set out to examine the efficacy of CTD for the structural characterization of synthetic polymers with a variety of monomer identities, adduct types, end group chemistry, and structural architecture.
The first study compared performance of CTD for the analysis of cation-adducted poly(propylene glycol) (PPG) in its sodiated, potassiated, and cesiated forms relative to CID of the same precursors on the same instrument. Results of this study indicate that CTD outperformed CID by generating structurally unambiguous fragment ion series regardless of the adduct identity. Collision induced dissociation of adducted PPG yielded few or no fragment ions because the metal adducts are weakly bound and readily lost, and the resultant neutral polymer molecules are not detectable. In contrast, CTD of the same PPG precursors achieved fragmentation at almost every position along the polymer backbone and provided full monomeric unit coverage through radical-induced high-energy fragmentation mechanisms that avoided the low-energy rearrangements of CID.
The second study compared CTD to both CID and a state-of-the-art technique of vacuum-ultraviolet photodissociation (VUVPD). Here, the target polymer was polyethylene nonylphenylether (PEGPh) adducted with sodium. Charge transfer dissociation outperformed VUVPD through superior signal-to-noise ratios in the product ion spectra and the formation of fragments along the entire polymer backbone. Other polymers, including poly(2-vinyl pyridine) (P2VP), poly(4-vinyl pyridine) (P4VP), and two polystyrene (PS) polymers with isobaric end groups were analyzed by CID and CTD. As before, CTD outperformed CID by generating fragment ion series at each location within each polymer’s monomeric unit. For the analysis of isobaric polymers of P2VP and P4VP, CTD activation outperformed CID regardless of the monomer or adduct type by producing multiple fragment ions. In some cases, CID provided few or no informative fragment ions at all. Additionally, the CTD product ion spectra of P2VP and P4VP provided insight into the possible radical-induced rearrangements for each polymer. The structure of P2VP enabled radical-directed 1,3- and 1,5-hydrogen shifts with hydrogen atoms on the polymer backbone, which caused extensive backbone cleavages of the polymer. In contrast, P4VP cannot undergo such transfers and is more resistant to fragmentation. Therefore, the two isobaric polymers are easily discernable via CTD. In both cases, the end group was also identified through neutral losses from the CTnoD peak. For the isobaric PS polymers, CTD provided extensive fragmentation with multiple fragment ion series, but CID of the same PS precursors generated no fragments between the precursor ions at m/z 1538 and the low mass cut-
off of ~m/z 300. However, neither technique provided fragmentation within the isobaric sec-butyl or isobutyl end-groups, so the PS polymers could not be distinguished.
The third study focused on the analysis of cyclic nylon (PA) analogues, including cylco-nylon-6 (cyclo-PA6), cyclo-nylon-6,6 (cyclo-PA66), cyclo-nylon-6,10 (cyclo-PA610), cyclo-nylon-6,12 (cyclo-PA612), and cyclo-nylon-6(3)T (cyclo-PA6(3)T). Collision induced dissociation was uninformative for the structural characterization of cyclo-PA610, cyclo-PA612, and cyclo-PA6(3)T, but produced adequate fragment ions for cyclo-PA6 and cyclo-PA66. The most dominant fragments were monomeric losses and fragment ions 18 Da heavier and lighter relative to the monomeric unit. For cyclo-PAs with larger repeat units, the lack of structurally informative fragment ions in CID is likely due to facile adduct loss, which results in a structurally useless sodium ion that falls below the LMCO and is therefore not detected. The challenge presented by loss of the charged adduct is avoided by the radical-induced dissociation technique of CTD. Charge transfer dissociation provided extensive polymer backbone coverage for all cyclic nylon analogs studied and therefore provides a viable approach to characterizing the backbone architecture of extremely robust polymers in the presence of a significantly weaker non-covalent adduct ion.
Future studies could employ molecular modeling and ion mobility studies to better understand the gas-phase conformation of synthetic polymer ions, which may provide further insight into the adduct location and polymer backbone architecture. Future studies could also incorporate isotope labeling or gas-phase ion spectroscopy to help confirm or elucidate the mechanisms and structures of some fragmentation pathways suggested here.
Recommended Citation
Ruiz, Emily, "Structural Characterization of Synthetic Polymers by Charge Transfer Dissociation-Mass Spectrometry (CTD-MS)" (2026). Graduate Theses, Dissertations, and Problem Reports (ETD). 13415.
https://researchrepository.wvu.edu/etd/13415