Polymerization of methyl methacrylate (MMA) initiated by eerie ammonium nitrate in combination with polytetrahydrofuran diol (PTHF-diol) and polycaprolactone diol (PCL-diol) has been investigated in aqueous nitric acid. PMMA-b-PTHF and PMMA-b-PCL block copolymers were obtained. Block copolymer yield was increased when using tetrabutyl ammonium hydrogen sulphate as a surfactant. The effects of nitric acid and eerie ions on the block copolymer yields were investigated. Block copolymers were characterized using GPC, H-1-NMR, DSC, TGA and fractional precipitation methods. (C) 1999 Elsevier Science Ltd. All rights reserved.