Reversible addition fragmentation chain transfer (RAFT) polymerization of methyl acrylate: Detailed structural investigation via coupled size exclusion chromatography - Electrospray ionization mass spectrometry (SEC-ESI-MS)

The on-line coupling of size exclusion chromatography (SEC) with electrospray ionization mass spectrometry (ESI-MS) was applied to study the polymeric product spectrum generated by the (strongly rate retarded) 2,2'-azobisisobutyronitrile (AIBN) and 1,1'-azobis(cyclohexanecarbonitrile) (ACHCN) initiated, cumyl dithiobenzoate (CDB) mediated methyl acrylate (MA) polymerization in detail. Products corresponding to the polymeric reversible addition fragmentation chain transfer (RAFT) agent and the combination and disproportionation termination products (with both cumyl, cyanocyclohexyl, and cyanoisopropyl end groups) along with a product stream arising from an oxidation process of the polymeric RAFT agent yielding sulfines and thioesters could be clearly identified. Termination products associated with the intermediate radical, that is, three- or four-armed star polymers, were not present. There is a degree of ambiguity over the disproportionation product of the macroRAFT radical. The experiments suggest that either the RAFT intermediate disproportionation product or the actual RAFT intermediate radical is present in the ESI-MS spectrum.