Iron catalyst in ppm scale: a novel NIR sensitized photoinduced ATRP

 
Atom transfer radical polymerization (ATRP) has received great importance for tailor-made synthesis of polymers and therefore also raw materials for coatings. A major disadvantage exists in the demand to use transition metal complexes at larger concentration. There exists therefore a demand to use systems comprising components directing the synthesis towards a greener design. Thus, the photo-ATRP has received increased interest since their design facilitates the use of metal ion complex in the ppm range. We report for the first time about a system comprising Fe(III) as catalyst for the photo-ATRP in the NIR range. A polymethine with barbital group sensitizes the catalytic ATRP cycle using 800 nm light for exposure. Metal complex functioned with tetrabutylammonium bromide (TBABr), tris(2-pyridylmethyl) amine and tris(4-methoxyphenyl) phosphine. TBABr showed the best performance. Polymers obtained exhibited dispersities between 1.1 and 1.3. Chain end fidelity of the polymers was confirmed by chain extension and block copolymerization experiments.