The stability of covalently immobilization of TEMPO on the polymer surface through ionic liquid linkage: a comparative and model research

Covalently immobilizing the active sites or ligands on a polymer surface is an efficient strategy to achieve a full use of expensive organic parts. In this work, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was anchored onto polystyrene beads through an ether bond or an ionic liquid bridge. We quantitatively compared their thermal stabilities at nitrogen atmosphere and their chemical stabilities in a biphasic oxidation surrounding. It was found that the ionic liquid-bridged TEMPO exhibited an additional advantage of stability and could be reused for 30 consecutive recycles with a conversion ratio above 90% without any significant loss under the condition of the Montanari oxidation system (NaClO/NaBr, CH 2 Cl 2 /water), and the overall reaction time exceeded 2700 min.