Synthesis of Lipid-α-End-Functionalized Chains by RAFT Polymerization. Stabilization of Lipid/Polymer Particle Assemblies

A functional dithioester including a phospholipid moiety (Lipid-DT) has been synthesized in a high yield (71% after purification) from a precursor chain transfer agent (CTA) and fully characterized. The RAFT polymerization of an acrylamide derivative, N-acryloylmorpholine (NAM), mediated by this Lipid-DT exhibits a prolonged induction period in comparison with a nonfunctional dithioester. This phenomenon is discussed in terms of steric shielding induced by the bulky lipid moiety of the CTA. Moreover, the lipid moiety located at the a-end of the chains has a strong influence on the size exclusion chromatography analyses in THF using a standard-based calibration, with the suspicion of a retention phenomenon. The well-defined structure of the lipid-end-functionalized polymer chains has been evidenced by MALDI-TOF mass spectrometry. Finally, these chains have been successfully incorporated into lipid/polymer particle assemblies (LipoParticles) that resulted in an improved stabilization in aqueous medium at relatively high ionic strength (300 mM).