Amine-Functionalized Polylactide–PEG Copolymers

The formation of halogenated carboxylic acid intermediate followed by a ring-closing reaction led to amino-functionalized asymmetrical lactide monomer. PEG-based functional diblock and triblock polylactides were synthesized via a controlled ring-opening polymerization in a solvent-free medium with high conversions (up to 96%), low polydispersities as low as 1.06, monomodal GPC traces, and short reaction time (only 1 h). No polymerization of symmetrical monomer, synthesized via condensation of (S)-(+)-CBZ-4-amino-2-hydroxybutyric acid, proved that the preferred site in the mechanism of ring-opening polymerization was found as a methyl site in asymmetrical lactide monomer. A highly efficient deprotection of copolymers was carried out in the presence of H2 gas and Pd/C catalyst without any degradation to obtain the corresponding free amine-functionalized aliphatic poly­(α-hydroxy acid)­s. These biodegradable thermosensitive polymers, suitable for any local therapy applications, were injectable around 42 °C (sol) and a gel just after cooling to body temperature. Faster hydrolytic degradation (up to 47% in 30 days) and more effective paclitaxel release from copolymer gels (up to 95% in 20 days) than well-known conventional PEG–PLA gels may make functional lactides a preferred candidate for developing controlled/sustained release of drugs from delivery vehicles.