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- CID-MS (1)
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- Mass spectrometry (1)
- Polymerization mechanisms (1)
- Polymers (1)
- RAFT (1)
- SEC/ESI-mass spectrometry (1)
Two decades after the introduction of matrix assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI), soft ionization mass spectrometry represents a powerful toolset for the structural investigation of synthetic polymers. The present review highlights the current state-of-the-art, covering the latest developments of novel techniques, enabling instrumentation as well as the important applications of soft ionization MS from the beginning of 2008. Special attention is paid to the role that soft ionization MS has played in the mechanistic investigation of radical polymerization processes since 2005.
We report the systematic investigation of a recently introduced one-pot radical transformation of methacrylate and acrylate-type polymers prepared via reversible addition fragmentation chain transfer (RAFT) polymerization into hydroxyl functional polymers. The simple reaction procedure involves stirring a solution of the RAFT functional polymer and an azo-initiator in tetrahydrofuran at elevated temperatures (T = 60 °C) in the presence of ambient air. Subsequent reduction of the formed hydroperoxide functional polymers to hydroxyl functional polymers is achieved in a one-pot procedure using triphenylphosphine. Polymers investigated in the current study are poly(methyl acrylate) (pMA), poly(butyl acrylate) (pBA), poly(isobornyl acrylate) (piBoA) and poly(tert-butyl acrylate) (ptBA) carrying a dithiobenzoate or phenyldithioacetate end terminius as well as a symmetrical trithiocarbonate mid chain function. Quantitative conversion into the hydroperoxyl and hydroxyl terminated product is observed when trithiocarbonate functional polymers are employed. In the case of dithiobenzoate and phenyldithioacetate functional acrylic polymers, some minor side products due to the oxidation of the RAFT end-group are generated. Size exclusion chromatography (SEC) and size exclusion chromatography–electrospray mass spectrometry (SEC-ESI-MS) were employed to monitor the progress of the reaction and to investigate the proposed reaction mechanism for the model polymers. When trithiocarbonate functional polymers are employed in the transformation reaction, the SEC analysis shows a bisection of the initial Mn. Collision induced dissociation (CID) MS experiments of the intermediate reaction products were conducted to gain in-depth information about the chemical structure. The new backbone linked hydroxyl group provides a versatile anchor for chemical end-group conversions and conjugation reactions with RAFT prepared polymers, alleviating problems with the rather limited ability of the dithioester end-group to undergo non-radical transformations.