Journal of Chromatography & Separation Techniques
Open Access
ISSN: 2157-7064
+44 1300 500008
ISSN: 2157-7064
+44 1300 500008
Laurence Charles
Posters-Accepted Abstracts: J Chromatogr Sep Tech
Mass spectrometry has become a powerful tool for polymer end-group analysis, a key step in the investigation of polymerization mechanisms. Detection of individual polymer molecules as ionic adducts allows monomer(s) to be identified based on the repeating mass increment(s) within the distribution while the combined end-group mass is evaluated from the mass value obtained upon extrapolation to zero monomer. Because synthetic polymer samples can exhibit distribution of molecular weights, end-groups and architectures, the use of mass analyzers of high resolving power is mandatory to minimize peak overlaps and to determine ion elemental composition based on accurate mass measurements. Finally, each end-group can be individually characterized by studying MS/MS data with regard to dissociation rules reported for the studied polymer family. In the present study, this MS-based analytical methodology was implemented to investigate ring-opening polymerization of cyclic ketene acetals by nitroxide-mediated polymerization (NMP), an alternative strategy to synthesize linear polyesters. Since targeted polymers were expected to hold a nitroxide termination, electro spray ionization (ESI) was used as a soft ionization technique to ensure the integrity of original end-groups. The cyclic ketene acetal was 5, 6-benzo-2-methylene-1,3-dioxepane (BMDO), and prior to any MS/MS investigation of unknowns, dissociation rules had to be established for these specific polyesters. Beside the expected pBMDO species, three main by-products were structurally characterized. The nature of the endgroups in these polymeric impurities revealed the occurrence of specific side-reactions, found to account for the increase of the polydispersity index with monomer conversion, an unusual feature in the NMP process.