Macromolecular engineering of polylactones and polylactides. 9. Synthesis, characterization, and applications of omega-primary amine poly(ε-caprolactone)

The synthesis and use of functional diethylaluminum alkoxides (Et2AlORX) as initiators for the ring-opening polymerization of ε-caprolactone have been investigated as a possible strategy to prepare omega-primary amino poly(ε-caprolactone) (PCL). In a first approach, an initiator containing ethylphthalimide as the functional-RX group has been synthesized. That protected amino group has been successfully attached at the end of PCL chains. The conversion of the phthalimide end group into a primary amine has however failed, whatever the experimental conditions. In an alternative approach, an alkyl bromide has been considered as the functional group to be attached to PCL chains, via the appropriate initiator. The end functionalization was quantitative and the bromo end group converted into an azido group which was subsequently reduced to the expected primary amine. Omega-primary amino PCL has proved to be an effective macroinitiator for the ring-opening polymerization of γ-benzylglutamate N-carboxy anhydride with the formation of a poly(caprolactone-b-peptide) diblock copolymer.