Sequencing of Side-Chain Liquid Crystalline Copolymers by Matrix-Assisted Laser Desorption/Ionization Tandem Mass Spectrometry

Abstract

Polyether based side-chain liquid crystalline (SCLC) copolymers with distinct microstructures were prepared using living anionic polymerization techniques. The composition, end groups, purity, and sequence of the resulting copolymers were elucidated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and tandem mass spectrometry (MS/MS). MALDI-MS analysis confirmed the presence of (CH3)3CO– and –H end groups at the initiating (α) and terminating (ω) chain end, respectively, and allowed determination of the molecular weight distribution and comonomer content of the copolymers. The comonomer positions along the polymer chain were identified by MS/MS, from the fragments formed via C–O and C–C bond cleavages in the polyether backbone. Random and block architectures could readily be distinguished by the contiguous fragment series formed in these reactions. Notably, backbone C–C bond scission was promoted by a radical formed via initial C–O bond cleavage in the mesogenic side chain. This result documents the ability of a properly substituted side chain to induce sequence indicative bond cleavages in the polyether backbone.

Application of a novel cyclic ion mobility‐mass spectrometer to the analysis of synthetic polymers: A preliminary evaluation

“…The use of MS for characterising complex polymeric materials often involves MS/MS approaches to investigate structural features . Typically, MS/MS experiments involve the selection of ions of interest using a quadrupole followed by the activation of the ions to effect fragmentation.…”

“…Different types of mass analyser are used in polymer analysis; in particular, a range of different tandem MS approaches are used in which two or more mass separation techniques are employed. Examples include a sector‐TOF mass spectrometer, a tandem quadrupole instrument, hybrid Orbitrap instruments, TOF/TOF instruments and quadrupole time‐of‐flight (QTOF) instruments . Tandem mass spectrometry techniques are most frequently used in the structural investigations of polymers because product ion patterns can provide information about monomer sequences, backbone architecture and end‐group identity.…”

Mass spectrometry of polymers: A tutorial review

“…The fragmentation patterns in the MS/MS spectra reported thus far have led to the articulation of polymer ion fragmentation mechanisms, which provide useful guidelines for the interpretation of newly acquired spectra (Chaicharoen et al, 2008; Gies et al, 2007; Gies & Hercules, 2014; Polce et al, 2008; Snyder et al, 2019; Solak Erdem et al, 2014; Wesdemiotis et al, 2011). Briefly, polymer ions dissociate through charge‐induced and charge‐remote pathways, depending on their composition and functional groups and the type of charge added in the ionization step (Wesdemiotis et al, 2011).…”

“…Polymer backbone nomenclature for linear homopolymers with defined α and ω chain ends. Reproduced from Polce and Wesdemiotis (2010) with permission from John Wiley & Sons, Inc. For the naming of copolymer fragments see Yol et al (2014) and Snyder et al (2019). [Color figure can be viewed at wileyonlinelibrary.com]…”