End-Functionalised 1-Vinyl-2-Pyrrolidone Oligomers Bearing Lactate Functions at One End.

1-Vinyl-2-pyrrolidinone (VP) oligomers bearing a lactate group at one end (PVP-L) were obtained by chain-transfer controlled radical polymerisation carried out in the presence of ethyl L-lactate as chain-transfer agent (CTA). Their number-average molecular weights were in the range 1500-4000 with molecular weight distributions ranging from 1.4 to 1.8. The chain transfer constant, CT, of the ethyl L-lactate/VP system was determined by monitoring the variation of PVP-L number-average molecular weight on conversion. The CT value so obtained was 1.03 × 10-2, which is by about one order of magnitude higher than the CT value previously determined for a seemingly similar system, namely methyl isobutyrate/1-vinyl-2- pyrrolidinone (1.64 × 10-3). The resultant PVP-L oligomers were thoroughly characterised by means of 1H and 13C NMR, in order to ascertain the regular presence of the lactate functions at one of their chain terminals. NMR characterisations gave results in full agreement with the proposed structure. Moreover, the molecular weight values determined by NMR very closely agreed with those obtained by SEC. Preliminary biological evaluations of the PVP-L oligomers showed a complete lack of toxicity.