Generation of end‐group information from polyethers by matrix‐assisted laser desorption/ionisation collision‐induced dissociation mass spectrometry

Ammonium adducts of trimethylsilyl-terminated poly(dimethylsiloxane) (CH 3 -PDMS) produced by electrospray ionization were submitted to collision induced dissociation and revealed a particular MS/MS behavior: the same three main product ions at m/z 221, 295, and 369 were always generated in very similar relative abundances regardless of the size of the precursor ion. Combining accurate mass measurements and ab initio calculation allowed very stable cyclic geometries to be obtained for these ionic species. Dissociation mechanisms were proposed to account for the three targeted ions to be readily generated in a two-step or a three-step reaction from any CH 3 -PDMS ammonium adducts. A second set of three product ions was also observed with low abundance at m/z 207, 281, and 355, which were shown in MS 3 experiments to be formed in secondary reactions. An alternative dissociation process was shown to consist of a concerted elimination of ammonia and methane and the need for a methyl of an end-group to be involved in the released methane molecule would account for this reaction to mainly proceed from the smallest precursor ions.

Section: Introductionmentioning

confidence: 99%

Tandem Mass Spectrometry of Trimethylsilyl-Terminated Poly(Dimethylsiloxane) Ammonium Adducts Generated by Electrospray Ionization

Fouquet

Humbel

Charles

2011

“…In the context of polymer analysis, recent papers describe the use of CID methodology for polymer ion characterization. Indeed, the CID behavior of different types of polymers, such as polyisobutylene [16], polystyrene [17], polymethylmethacrylate [18], polyether [19], and polyester [10 -13] were investigated.…”

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confidence: 99%

Mechanistic study of the collision-induced dissociation of sodium-cationized polylactide oligomers: A joint experimental and theoretical investigation

Winter

Lemaur

Marsal

et al. 2010

The low-kinetic energy collision-induced dissociation (CID) behavior of different sodiumcationized polylactide (PLA) oligomers was thoroughly investigated to shed some light on the analytical potentialities of CID experiments in the context of polymer characterization. Indeed, investigation of several end-groups modified PLA reveals that, in addition to the expected end-group specific dissociations, collisionally-excited PLA.Na ϩ suffer from a backbone cleavage. The so-obtained sodium-bound dimer cations consecutively undergo the loss of a monomeric residue that corresponds to neutral acrylic acid. The experimental observations, performed on a hybrid Q-ToF instrument, were totally corroborated by a theoretical study involving DFT calculations, molecular mechanics, and molecular dynamics calculations. . Such biodegradable polymers are often designed to degrade hydrolytically so that most of the widely studied biodegradable polymers belong to the polyester family and include polylactide (PLA), polyglycolide (PG), and associated copolymers [3]. PLA is certainly one of the most important synthetic biodegradable and biocompatible polymers attracting a huge interest for new and versatile synthetic procedures [4]. Polylactide and poly-(lactic acid) are, respectively, obtained by ring-opening polymerization (ROP) of lactide, the cyclic dimer of lactic acid, or by polycondensation of lactic acid.In the course of our research on the polymerization of lactide using non-organometallic catalysts such as N-heterocyclic carbenes, superbases, fluorinated tertiary alcohols, thiourea derivatives, and phosphazenes [5][6][7], we decided to explore the potential of mass spectrometry to provide an in-depth characterization of synthetic polymers in addition to well-established methodologies, such as gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR). Electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) represent the most significant recent developments in ionization techniques for mass spectrometry analysis of synthetic polymers [8]. State-of-the-art mass spectrometry tools hold the promise of providing not only absolute molecular mass distributions [9] but also qualitative end-group and repeat-unit composition [10], as well as structural information such as branching and intramolecular ring formation [11]. By definition, MS experiments provide the masses of the individual oligomers prepared during the polymer synthesis. On the basis of the m/z ratio of the detected cationized oligomers, compositional pieces of information such as the number and type of monomer units but also the nature of the incorporated end-groups can be derived. Nowadays, tandem mass spectrometry (MSMS) is emerging as an essential analytical methodology when accurate structural characterization of polymers cannot be unambiguously derived from single-stage MS experiments [12]. Recent MSMS investigations were successfully used to characterize individual functional groups of new polymers, to make

“…Dissociation pathways have been studied for a large variety of polymers, such as PEO [11][12][13][14][15][16][17][18][19][20][21][22][23][24], PS [20,[23][24][25][26][27][28][29][30], or poly(methylmethacrylate) (PMMA) [20, 21, 23, 30 -32]. In contrast, few MS studies have been reported for PMAA and most of them focused on the analysis of volatile thermal degradation products of the polymer [33,34].…”

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confidence: 99%

Tandem mass spectrometry of poly(methacrylic acid) oligomers produced by negative mode electrospray ionization

Giordanengo

Viel

Allard-Breton

et al. 2009

Dissociation of small poly(methyl acrylic acid) (PMAA) anions produced by electrospray was characterized by tandem mass spectrometry. Upon collisional activation, singly, and doubly deprotonated PMAA oligomers were shown to fragment via two major reactions, dehydration and decarboxylation. The elimination of a water molecule would occur between two consecutive acid groups in a charged-remote mechanism, giving rise to cyclic anhydrides, and was shown to proceed as many times as pairs of neutral pendant groups were available. As a result, the number of dehydration steps, together with the abundance of the fragment ions produced after the release of all water molecules, revealed the polymerization degree of the molecule in the particular case of doubly charged oligomers. For singly deprotonated molecules, the exact number of MAA units could be reached from the number of carbon dioxide molecules successively eliminated from the fully dehydrated precursor ions. In contrast to dehydration, decarboxylation reactions would proceed via a charge-induced mechanism. The proposed dissociation mechanisms are consistent with results commonly reported in thermal degradation studies of poly(acrylic acid) resins and were supported by accurate mass measurements. These fragmentation rules were successfully applied to characterize a polymeric impurity detected in the tested PMAA sample. (J Am Soc Mass