MACROMOLECULAR ENGINEERING OF POLYLACTONES AND POLYLACTIDES .16. ON THE WAY TO THE SYNTHESIS OF OMEGA-ALIPHATIC PRIMARY AMINE POLY(EPSILON-CAPROLACTONE) AND POLYLACTIDES

Since bromides are well-known precursors of primary amines, diethylalu minum 12-bromo-1-dodecyl oxide has been prepared and used as an initia tor for the ring-opening polymerization of epsilon-caprolactone and L- lactide. Under strictly controlled conditions, the end-functionalizati on of the polyesters is quantitative and the bromo end-group is easily converted into an azide group whatever the polymeric backbone. The su bsequent reduction of the azide into the expected primary amine has be en investigated by catalytic transfer hydrogenation (CTH) in DMF and b y hydrolysis in the presence of triphenylphosphine in THF, respectivel y. The hydrolysis reaction (P phi(3)/H2O) is perturbed by a coupling r eaction, which involves a protonated secondary amine and leads to a tw ofold increase in the polyester molecular weight. The CTH method gives rise to the expected omega-NH2 poly(epsilon-caprolactone), in contras t to polylactide which seems to be unstable toward the nascent amine e nd group. Whatever the polarity of the medium (DMF or THF), aminolysis of polylactides is observed to occur and leads to the formation of an internal amide. (C) 1994 John Wiley and Sons, Inc.