title: End-group rearrangements in poly(propylene sulfide) matrix-assisted laser desorption/ionization time-of-flight analysis. Experimental evidence and possible mechanisms.
abstract: BACKGROUND
  Polysulfides [poly(1,2-alkylene sulfides)] are oxidation-responsive polymers that are finding application in drug release and biomaterials. The precise knowledge of their macromolecular characteristics is of the essence in view of their application to biological systems.
  
  
  METHODS
  Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with and without silver trifluoroacetate was used to characterize a series of polymers with increasing molecular weight in the range 1000-4000 g/mol and with low polydispersity (<1.12).
  
  
  RESULTS
  Well-resolved peaks and accurate mass-measured values were obtained using a 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix, but significant fragmentations took place in the absence of silver as a cationizing reagent. Elimination reactions appeared to occur at terminal groups and limited depolymerization could be recorded. Interestingly, the most common fragmentation pathway seemed to be based on an as-yet-unreported process of hydrogen transfer requiring the presence both of ester groups and of thioethers.
  
  
  CONCLUSIONS
  The use of an appropriate cationizing reagent (silver trifluoroacetate) appeared to suppress end-group eliminations; we hypothesize that this action is based on the involvement of the terminal groups in silver chelation.
authors.affiliation: School of Materials, University of Manchester, Oxford Road, Manchester M13 9PT, UK.
authors.forename: Enrique
authors.initials: E
authors.lastname: Lallana
authors.forename: Tiziana
authors.initials: T
authors.lastname: Ferreri
authors.forename: Sabrina C
authors.initials: SC
authors.lastname: Carroccio
authors.forename: Ana M
authors.initials: AM
authors.lastname: Puga
authors.forename: Nicola
authors.initials: N
authors.lastname: Tirelli
mesh_terms: D008958:Models, Molecular; D008970:Molecular Weight; D011108:Polymers / Q000032:analysis / Q000737:chemistry*; D012834:Silver / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013440:Sulfides / Q000737:chemistry*; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D011108:Polymers; D013440:Sulfides; C522256:poly(propylene sulfide); D012834:Silver; D014269:Trifluoroacetic Acid