Synthesis and characterization of amphiphilic PLA-(PαN3CL-g-PBA) copolymers by ring-opening polymerization and click reaction

The present study prepared novel amphiphilic block-graft PDLLA-b-(PαN3CL-g-PBA) and PLLA-b-(PαN3CL-g-PBA) functional polyesters, containing a hydrophilic poly(α-azido-ε-caprolactone-graft-alkyne) (PαN3CL-g-alkyne) segment and a hydrophobic poly(dl-lactide) (PDLLA) or poly(l-lactide) (PLLA) segment, using ring-opening polymerization of α-chloro-ε-caprolactone (αClCL) with a hydroxyl-terminated macroinitiator of PDLLA or PLLA, substituting pendent chloride with sodium azide. The copolymers were subsequently used for grafting of 2-propynyl-terminal benzoate moieties by way of Cu(I)-catalyzed Huisgenʹs 1,3-dipolar cycloaddition, thus producing a “click” reaction. Differential scanning calorimetry (DSC) and 1H NMR, FT-IR, and GPC examined the characteristics of the copolymers. The critical micelle concentration (CMC) ranged from 2.7 mg L−1 to 24.6 mg L−1 at 25 °C and the average micelle size ranged from 106 nm to 297 nm. The length of the hydrophilic segment and the configuration of the lactide both influenced micelle stability. The micelle of PLLA-b-(PαN3CL-g-PBA) provided high drug entrapment efficiency and loading content. The results from in vitro cell viability assays indicated that PLA-b-(PαN3CL-g-PBA) shows low cytotoxicity.