NMR Spectroscopy and MALDI-TOF MS Characterisation of end-functionalise PVP Oligomers Prepared with Different esters as chain transfer agents

Ester-functionalised poly(1-vinylpyrrolidin-2-one) (PVP) oligomers obtained by radical polymerisation in methyl propionate, diethyl malonate and diethyl 2-methyl-malonate were chracterised by NMR spectroscopy, and MALDI-TOF mass spectrometry. The chain-transfer constants were determined as 5.54 × 10-4, 1.22 × 10-3 and 1.70 × 10-2, respectively, by measuring the variation of the number-average molecular weight on conversion. These values were compared with those of methyl isobutyrate (1.65 × 10-3) and ethyl lactate (1.03 × 10-2), which had been previously determined. A clear dependence was found on the reactivity of the mobile hydrogen atoms α with the ester group. All of the macromolecules carried a single ester function. Therefore, the re-initiation step by the CTA-derived radicals overwhelmingly prevailed over initiation by the primary radicals.