Synthesis and characterization of amphiphilic functional polyesters by ring-opening polymerization and click reaction

During this work we have prepared novel amphiphilic graft-block (PαN ₃CL-g-alkyne)-b-PCL functional polyesters, comprising poly(α-azido - caprolactone-graft-alkyne) (PαN ₃CL-g- alkyne) as the hydrophilic segment and poly(-caprolactone) (PCL) as the hydrophobic segment, by ring-opening polymerization of -caprolactone (-CL) with hydroxyl-terminated macroinitiator PαClCL, substituting pendent chloride with sodium azide. The copolymers were subsequently used for grafting of 2-propynyl-terminal alkyne moieties by the Cu(I)-catalyzed Huisgen's 1,3-dipolar cycloaddition, thus producing a "click" reaction. ¹H NMR, FT-IR, GPC, and differential scanning calorimetry (DSC) examined the characteristics of the copolymers. Grafting of PMEs or PMPEGs onto the PαN ₃CL-b-PCL caused these amphiphilic copolymers to self-assemble into micelles in the aqueous phase. Fluorescence, dynamic light scattering (DLS) and transmission electron microscopy (TEM) then examined these micelles. The critical micelle concentration (CMC) ranged from 8.2 mg L ^-1 to 39.8 mg L ^-1 at 25 °C and the average micelle size ranged from 140 to 230 nm. The hydrophilicity and length of the hydrophilic segment influenced micelle stability. The current study describes the drug entrapment efficiency and drug loading content of the micelles, dependent on the composition of graft-block polymers. The results from in vitro cell viability assays indicated that (PαN ₃CL-g-alkyne)-b-PCL shows low cytotoxicity.