Exploring chromophore tethered aminoethers as potential photoinitiators for controlled radical polymerization

Compounds 1–4 containing various light absorbing chromophores attached covalently to a hindered aminoether (2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) aminoether) were synthesized, and their photochemistry and photophysics studied in an attempt to develop photoinitiators for radical “living” polymerization. Significant shortening of the chromophore's triplet lifetime was observed in 1–4 as compared to analogous compounds containing no alkylated TEMPO moiety, which suggests an intramolecular quenching of the excited chromophore by the aminoether functionality. The efficiency of the quenching process depends on the chromophore. Employing 1–4 as unimolecular photoinitiators for styrene “living” polymerization was proven to be difficult due to rapid quenching of the excited state of the initiator by this monomer. Compound 4 was demonstrated as an initiator for controlled photopolymerization of methyl methacrylate.