A kinetic study of atom transfer radical polymerization of styrene with bis(2-pyridyl)ethylenedimethanimine derivative ligands

Atom transfer radical polymerization (ATRP) of styrene was carried out with multidentate nitrogen-based ligands, namely N,N'-bis[phenyl(pyrid-2-yl) methylene]ethane-1,2-diamine (BPDA) and N, N'-bis[methyl(pyrid-2-yl) methylene]ethane-1,2-diamine (BMDA), and catalyst systems at catalyst/ligand molar ratios of 1/0.33, 1/0.5, 1/1, and 1/1.5 by using 2 different initiators, (1-bromoethyl) benzene (BEB) and ethyl-2-bromopropionate (EBP). Linear first-order kinetic plots were observed for ATRP of styrene upon using BPDA as a ligand with both initiators. Even though the linear slopes indicate that radical concentration remains constant during reactions, high molecular weights were obtained at low conversion and showed a linear relation thereafter. To investigate the molecular weight effect, reactions were also performed in the presence of (1-bromoethyl) benzene initiator in dimethylformamide (DMF) for BPDA and in toluene for BMDA using a catalyst/ligand ratio of 1/1.