Amine Additives for Fast Living Radical Polymerization of Methyl Methacrylate with RuCl2(PPh3)3

A series of amines were effective as additives for the control and rate enhancement of the living radical polymerization of methyl methacrylate (MMA) with RuCl 2 (PPh 3 ) 3 . On addition of n -Bu 3 N and n -Bu 2 NH, the polymerization with R−Cl/RuCl 2 (PPh 3 ) 3 in toluene at 80 °C reached 90% conversion in 50 h and 94% in 20 h, respectively, while only 46% in 120 h without additives. The polymers obtained with n -Bu 3 N and n -Bu 2 NH had controlled molecular weights that increased in direct proportion to monomer conversion and narrow MWDs ( M w / M n = 1.1−1.2). This is in sharp contrast to the uncontrolled molecular weights and broad MWDs ( M w / M n = 1.7−2.0) obtained in the additive-free systems. Primary amines like n -BuNH 2 and cyclic secondary amines like piperidine induced much faster polymerizations to result in broad MWDs ( M w / M n = 1.7−1.8). Other additives such as pyridines, amides, alcohols, phenols, esters, and dimanies were not effective as additives for the ruthenium-catalyzed polymerizations. Interactions between the added amines and RuCl 2 (PPh 3 ) 3 were observed by 1 H NMR analysis of the mixtures, where the amines coordinate to the ruthenium center and form highly active mononuclear ruthenium complexes.