Direct one-pot synthesis of poly(ionic liquid) nanogels by cobalt-mediated radical cross-linking copolymerization in organic or aqueous media

Abstract

Nanogels of controlled kinetic chain length were synthesized by cobalt-mediated radical cross-linking copolymerization (CMRccP) involving a vinyl monomer and a divinyl cross-linker. This strategy was first validated to achieve neutral poly(vinyl acetate) nanogels by CMRccP of vinyl acetate and divinyl adipate as a cross-linker at 40 °C in the presence of an alkyl-cobalt(III) serving both as an initiator and a controlling agent using ethyl acetate as a solvent. Poly(ionic liquid) nanogels were then directly obtained by CMRccP of N-vinyl-3-ethyl imidazolium bromide in the presence of 1,13-divinyl-3-decyl diimidazolium bromide as a cross-linker. CMRccP experiments could be conducted either in an organic solvent using dimethyl formamide or, more interestingly, in aqueous solution, demonstrating the robustness and versatility of this one-step process. Chain extensions of PIL nanogels were also carried out in water, forming core–shell structures, thus opening new avenues in the design of functional nanogels.