Synthesis of H-3 and fluorescence-labelled poly (DL-lactic acid)

The novel polymer modification method based on the activation of an aliphat ic polyester chain by using lithium diisopropylamide at low temperature to form a polycarbanion bearing nucleophilic sites in a position alpha to the carbonyl groups was applied to rac-poly (lactic acid), PLA(50), to label th is polymer with radioactive tritium atoms or with a fluorescent dye. Despit e simultaneous partial chain degradation, radioactive PLA(50) and fluoresce nt PLA(50) with (M) over bar (n) = 14 000 g mol(-1) (M) over bar (w)/(M) ov er bar (n) = 1.9 and (M) over bar (n) = 32 000 g mol(-1) (M) over bar (w)/( M) over bar (n) = 2.4, respectively, were obtained. The specific activity o f the final compound was 3.7 mu Ci g(-1) that squared with 0.3 parts per th ousand substitution reaction. The fluorescent polymer was substituted with 0.25% ratio. This work shows that the LDA activation method appears to have considerable potential. Copyright (C) 2001 John Wiley & Sons, Ltd.