Structured semifluorinated polymer ionic liquids for metal nanoparticle preparation and dispersion in fluorous compartments

摘要

Structured semifluorinated polymer ionic liquids (FPILs) contain a flexible hyperbranched polyether core connected with a covalently attached shell of imidazolium cations and perfluorinated alkyl chains at their periphery. In a facile synthesis, alkylation of tosylated poly(3-ethyl-3-hydroxymethyloxetane) (PEHO) converts 1-(n-1H,1H,2H,2H-perfluorooctyl)imidazole into hyperbranched FPILs. They form fluorous compartments for the preparation and effective dispersion of Ag and Au nanoparticles. Only in the presence of the nonfluorinated (PIL) and the semifluorinated polymeric ionic liquids (FPIL), Ag and Au cations are reduced in N,N-dimethylacetamide (DMAC) to form stable metal particle dispersions with average nanoparticle sizes varying between 2 and 13 nm. In the absence of the hyperbranched PEHO core, the corresponding low molecular weight ILs fail to afford stable nanoparticle dispersions. In contrast to the corresponding nonfluorinated PIL, FPIL enables to produce both spherical and flaky uniformly dispersed nanoparticles as a function of the FPIL content. This is attributed to the self-assembly of FPIL at nanoparticle interfaces. Designing nanostructured FPILs and FPIL-mediated metal nanoparticle dispersion is of interest to fluorous multiphase catalysis in fluorous compartmentalized ionic systems without requiring the use of fluorinated solvents.