Abstract
Synthetic polymers are the products of humans’ attempts to imitate nature’s gigantic molecular chain architectures. The extended variety of building blocks and reaction mechanisms resulted in a plethora of different polymeric architectures. The biggest challenge for polymer chemists is to develop an understanding of the relation between the chemical structure
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of polymers and their physicochemical and mechanical properties. Mass spectrometry (MS) can provide detailed information about the elemental composition, monomer unit and end-group structure of polymeric systems. However, it also has its limitations. The analysis of high molar mass and/or disperse and/or structurally complicated synthetic polymers remains a big challenge. This thesis tries to address this challenge by controlling the charge state and energy of synthetic polymers during MS. Chapter 2 gives a general introduction to polymer analysis and MS. Besides this introduction, Chapter 2 presents some examples of current practical state-of-the-art MS, and liquid chromatography coupled to MS, methods for the analysis of synthetic polymers. Chapter 3 provides an example of the current performance of LC coupled to tandem MS (MS/MS) in the analysis of structurally complicated polymers, such as vegetable oil ethoxylates. Chapter 4 presents the method development to achieve an accurate and reproducible control of the applied excitation energy in a quadrupole ion trap. The method is checked by studying the required excitation energy for fragmentation of poly(ethylene glycol)s as a function of their size. This dependence is shown to be linear and in agreement with other MS instruments where the applied excitation energy can be controlled in a more accurate way. In Chapter 5, the methodology for accurate and reproducible control of the applied excitation energy is used to discriminate between different polymer classes. It is shown that discrimination is achieved by determining a “characteristic” parameter (i.e., the characteristic collision voltage (CCV)), which is related to the polymer’s structure and expresses the stability of the respective polymer ion upon excitation. The determination of the CCV is then used in the analysis of a mixture of a structurally complicated copolymer system and various, nominally isobaric, homopolymers, which cannot be discriminated by conventional MS and MS/MS methods. Chapters 6, 7 and 8 present the study of non-covalent complex ions of high molar mass synthetic polymers and molecules containing ammonium functionalities. These complex ions appear to have a preference for low charge states. Chapter 6 and 7 present the investigations of the parameters that influence the formation of these low charge state adducts ions. Chapter 8 presents the behavior of these non-covalent complex ions upon activation at both low and relatively high collision regimes. The amount and type of fragments ions is strongly influenced by the structure of the ammonium ion. The results show that MS/MS of these non-covalent complex ions can be used as a source of polymer structural information
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