Polymerizations of methyl methacrylate (MMA), cyclohexyl methacrylate (CHMA), stearyl methacrylate (SMA), butyl acrylate (BuA), and 2-ethylhexyl acrylate (2-EHA) were carried out to examine the maximization of their molecular weights using a minute amount of a unique initiator, SmMe(C5Me5)(2)(THF), under various conditions. As a result, poly(MMA) with a molecular weight, M-n, of 135 X 10(4), with low polydispersity (MwIMn = 1.12) and high syndiotacticity (85%) was obtained in high yield (86%) when we used a [M](o)/[I](o) ratio of 8000 mol / mol at 0 T. CHMA also produced a high molecular weight polymer (M-n = 157 X 10(4), MwIMn = 1.2) in a high yield (99%), while SMA gives only low molecular weight polymers (M-n = 1.3 X 10(4), MwIMn = 1.17) in relatively low yield (78%). BuA and 2-EHA also produced high molecular weight polymers (M-n = 157 X 10(4), M(w)lM(n) = 1.21; M-n = 90.5 X 10(4), MwIMn = 1.05, respectively) in high yields using a [M](o)/[1](o) ratio of 8000, but their stereoregularities were very poor. As an extension of this study, tri-block copolymerizations of CHMA/BuA/CHMA were explored to obtain rubber-like elastic polymers. (C) 2002 Elsevier Science B.V. All rights reserved.