An amphiphilic PEG-b-PFPE-b-PEG triblock copolymer: synthesis by CuAAC click chemistry and self-assembly in water

Abstract

A new PEG₂₀₀₀-b-PFPE₁₂₀₀-b-PEG₂₀₀₀ amphiphilic triblock copolymer was synthesized by copper(I)-catalyzed alkyne–azide cycloaddition (CuAAC). The microstructure of this ABA triblock copolymer was unequivocally characterized by NMR spectroscopy. Diffusion-ordered spectroscopy (DOSY) NMR experiment revealed that ¹H resonances belonging to PEG and PFPE are aligned on the same horizontal line, thus implying that all these signals are due to the same macromolecule whose diffusion coefficient is lower than that of PEG and PFPE homopolymers. Thanks to its semi-fluorinated backbone bearing robust triazole rings, the PEG₂₀₀₀-b-PFPE₁₂₀₀-b-PEG₂₀₀₀ triblock copolymer exhibits good thermal stability with no significant weight loss until 275 °C under air. This triblock copolymer undergoes self-assembly into micelles (D = 10–20 nm) in aqueous solution as confirmed from cryogenic-temperature transmission electron microscopy, DOSY experiment in D₂O, and dynamic light scattering. The critical micelle concentration was determined by pyrene fluorescence assay, and was found to be 0.1 mg mL⁻¹.