Polyolefins with light responsive activities/functionalities through nitroxides grafting

The radical coupling between a macroradical formed onto the backbone of a polymer and a functional nitroxide is a very interesting tool to graft specific functionalities onto polyolefin backbone. 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) derivatives have been successfully used in post-modification processes of polyethylene-based materials to graft polar species, like as -OH or ester groups, by coupling reaction with polymer macroradicals which were formed by H-abstraction through peroxide addition. For examples the 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (HO-TEMPO) and the 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (BzO-TEMPO) have been used to functionalize the polyolefin with good efficiency and, really important, this approach allows to keep under control the undesired degradation and cross-linking reactions which generally affect the free radical functionalization processes of polyolefins in the melt. Particularly the macroradicals coupling was completely hindered