Amphiphilic block copolymers, methoxy polyethylene glycol-b-poly(butyl methacrylate), were synthesized via activators regenerated by electron transfer for atom transfer radical polymerization(ARGET ATRP) of butyl methacrylate (BMA), where pentamethyldiethylene triamine (PMDETA) was utilized as the ligand. The results show that the minimum amount of the catalyst required in the ARGET ATRP of BMA with a high degree of control depends upon the molar ratio of [catalyst](0)/[initiator](0). With PMDETA as the ligand and methoxy polyethylene glycol 2-bromo-iso-butyrate (MPEG-Br) as the macro-initiator, the ratio of [CuBr2](0)/[MPEG-Br](0) should be higher than 0.025:1. At this value, the copper catalyst level can be lowered to 50 ppm when the degree of polymerization of the BMA segment is set at 500. Reaction conditions that impact the controllability of the polymerization and the corresponding properties of the block copolymers were investigated. (C) 2013 Elsevier Ltd. All rights reserved.