MONODISPERSE POLYMERIZATIONS AND COPOLYME RIZATIONS INITIATED BY RARE-EARTH-METAL COMPLEXES

Organometallics of rare earths such as (C5Me5)2LnR (Ln = Y, Sm, Yb, Lu ; R = H, Me) initiated the living polymerizations of alkyl methacrylat es and alkyl acrylates for the first time to afford high molecular wei ght polymers (M(n) > 500, 000) with extremely narrow molecular weight distribution (M(w)/M(n) < 1. 05). The 1 : 2 reaction of SmH(C5Me5), wi th MMA provides a single crystal and its X-ray analysis revealed the f ormation of an 8-membered ring complex where one end is bound with eno late form and the other end by the coordination of ester group of MMA. Based on these findings we propose coordination anionic polymerizatio n mechanism for this reaction. SmMe(C5Me5)2(THF) and YOMe(C5Me5)2(THF) were also able to conduct the living polymerizations of beta-propiola ctone, delta-valerolactone and epsilon-caprolactone. Organo rare earth metal (II) complex with bulky auxiliary ligand, Me2Si (2-Me3Si-4-tBu- C5H2)2Sm, as well as rare earth metal (III) complexes, Me2Si[2,4-(Me3S i)2C5H2]2LnCH(SiMe3)2 (Ln = La, Sm), were found to conduct the polymer ization of ethylene to give high moleculr weight polymers with narrow molecular weigt distribution.