Synthesis of nanogels of poly(ε-caprolactone)-b-poly(glycidyl methacrylate) by click chemistry in direct preparation

• The “click” chemistry was used for core cross-linked micelles of PCL-b-PGMA-N3.
• Nanogels were prepared with a single step in the nonselective solvent.
• Fine spherical nanogels were obtained without pre-assembly in the solution.
• The nanogel formation could be controlled with adjusting reaction conditions.

The controlled synthesis of nanogels was carried out in a single step using “click” chemistry. Poly(ε-caprolactone)-b-poly(glycidyl methacrylate) (PCL-b-PGMA) block copolymers were prepared by the combination of ring-opening polymerization and the reversible addition fragmentation chain transfer polymerization, and subsequently functionalized with azido groups. The direct formation of nanogels of the azide-functionalized PCL-b-PGMA-N3 was controlled using dipropargyl adipate (DPA) as a cross-linking agent from the homogeneous solution in a nonselective solvent. The results revealed that the formation of macrogels or nanogels with core cross-linked block copolymers depends on the concentration of the block copolymer and the cross-linker and the chain length of the PGMA-N3 block, so that the preparation of nanogels was manipulated simply with adjusting the molar ratio of alkyne to azide groups. The nanogels were confirmed by nuclear magnetic resonance, X-ray photoelectron spectroscopy, transmission electron microscopy, dynamic light scattering analyses and gel permeation chromatography. DPA was found to cross-link the block copolymer effectively and afford robust nanostructures, while leaving click-readied azide functionalities throughout the core domain, which are proposed to be readily available for further chemical modification.

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