Cu-Catalyzed Atom Transfer Radical Polymerization in the Presence of Liquid Metal Micro/Nanodroplets

Micro/nanodroplets of the liquid metal (LM) eutectic Ga-In alloy (EGaIn) were employed in atom transfer radical polymerization (ATRP) in organic solvents with low ppm (parts per million) loading of Cu catalysts. ATRP in the presence of EGaIn produced well-defined polymers (dispersity <1.1) that could be easily separated from EGaIn via centrifugation. Voltammetric analysis revealed that EGaIn micro/nanodroplets reduced CuII complexes to CuI complexes, which acted as ATRP activators. A key distinction from previously reported LM-mediated radical polymerizations is that this process did not require external forces, such as ultrasound sonication. EGaIn droplets also activated dormant alkyl bromide species. However, this reaction was ∼6 orders of magnitude slower than the corresponding activation by CuI complexes, resembling SARA (supplemental activators and reducing agents) ATRP.