Structural characterization of nitroxide-terminated poly(n-butyl acrylate) prepared in bulk and miniemulsion polymerizations

The structure of "living" poly(n-butyl acrylate) homopolymers prepared via nitroxide-mediated controlled radical polymerization in bulk and in miniemulsion at 112 degreesC was examined by SEC, NMR, and MALDI-TOF mass spectrometry in order to study the influence of chain transfer to polymer. The absence of detectable terminal unsaturation was confirmed by proton NMR. The branched structure was observed by C-13 NMR. MALDI-TOF MS demonstrated that the majority of chains, even at high conversion, had the ideal structure with one initiator fragment and one nitroxide end group. From these results, we concluded that intramolecular chain transfer occurred (presumably by backbiting) and was the predominant mechanism throughout the polymerization at 112 degreesC.