LIVING POLYMERIZATIONS OF POLAR AND NONPOLAR MONOMERS BY THE CATALYSIS OF ORGANO RARE-EARTH-METAL COMPLEXES

This review article deals with the rare earth metal initiated polymeri zation of polar and nonpolar monomers in living fashion (''living'' me ans very active without termination and chain transfer reaction) to gi ve monodisperse high molecular weight polymers at high conversion. A t ypical example is seen in the polymerization of methyl methacrylate wi th [SmH(C5Me5)(2)](2) or [LnMe(C5Me5)(2)(THF)] (Ln = Sm, Y, and Lu), g iving high molecular weight syndiotactic polymers (M-n > 500000, syndi otacticity > 95%) quantitatively at low temperature (-95 degrees C). T he initiation mechanism was discussed on the basis of X-ray analysis o f the 1 : 2 adduct (molar ratio) of [SmH(C5Me5)(2)]2 with MMA. Living polymerizations of alkyl acrylates (methyl acrylate, ethyl acrylate, a nd butyl acrylate) were also possible by the catalysis of [LnMe(C5Me5) (2)(THF)] (Ln=Sm, Y); i.e. poly(methyl acrylate) M-n=48x1O(3), M-w/M-n =1.04, poly(ethyl acrylate) M-n=55x10(3), M-w/M-n=1.04, and poly(butyl acrylate) M-n = 70 x 10(3), M-w/M-n = 1.05. By taking advantages of t he living polymerization ability, we attempted ABA triblock copolymeri zation of MMA/butyl acrylate/MMA to obtain rubber-like elastic polymer s. Lanthanum alkoxide(III) has good catalytic activity for the polymer ization of alkyl isocyanates (M-n > 10(6), M-w/M-n = 2.08). Monodisper se polymerizations of lactones, lactide, and various oxiranes were als o achieved by polymerization with rare earth metal complexes. C-1 symm etric bulky organolanthanide(III) complexes such as {SiMe2[2(3),4-(SiM e)(2)C5H2](2)LnCH(SiMe3)(2)} (Ln = La, Sm, and Y) show high activity f or linear polymerization of ethylene. Organolanthanide( complexes such as racemic (SiMe2[2-SiMe3-4-tBu-C5H2](2)Sm(THF) as well as C-1 symmet ric{SiMe2[2(3),4-(SiMe3)(2)C5H2](2)Sm(THF)} were also found to have hi gh activity for the polymerization of ethylene. Thus, polyethylene of M-n > 10(6) (M-w/M-n = 1.6) was first obtained by using {SiMe2[2(3),4- (SiMe3)(2)C5H2](2)Sm(THF)}. 1,4-Cis conjugated diene polymerization of 1,3-butadiene and isoprene became available by the efficient catalyti c activity of NdCl(C5H5)(2)/AlR3 or Nd(octanoate)(3)/AlR3. The Ln(naph thenate)(3)/AliBu(3) system allows selective polymerization of acetyle ne in cia-fashion. Utilyzing the fact that rare earth metal initiated living polymerization proceeds for both polar and nonpolar monomers, r esearchers have attempted to block copolymerization of ethylene with M MA or lactones yielding polyethylene derivatives having high chemical reactivity.