Synthesis of 3H and fluorescence‐labelled poly ( DL ‐Lactic acid)

The novel polymer modification method based on the activation of an aliphatic polyester chain by using lithium diisopropylamide at low temperature to form a polycarbanion bearing nucleophilic sites in a position α to the carbonyl groups was applied to rac‐poly (lactic acid), PLA50, to label this polymer with radioactive tritium atoms or with a fluorescent dye. Despite simultaneous partial chain degradation, radioactive PLA50 and fluorescent PLA50 with Mn=14000 g mol−1, Mw/Mn=1.9 and Mn=32 000 g mol−1, Mw/Mn=2.4, respectively, were obtained. The specific activity of the final compound was 3.7 µCi g−1 that squared with 0.3‰ substitution reaction. The fluorescent polymer was substituted with 0.25% ratio. This work shows that the LDA activation method appears to have considerable potential.