Mitsufumi Nodono

Chain transfer polymerization of methyl methacrylate initiated by organolanthanide complexes

A novel chain transfer polymerization mediated by Cp 2 *Sm(III) species and organic acids is described. The chain transfer polymerization involves the reaction of organic acids such as thiols or ketones with an active bond between samarium(III) and the enolate in a living chain and of poly(methyl methacrylate) (PMMA). This chain transfer reaction resulted in termination of the living chain end and the regeneration of the active initiator which would consist of (C 5 Me 5 ) 2 Sm(III) and deprotonated organic acids. The chain transfer polymerization was confirmed by turnover numbers (TON). tert-Butyl thiol exhibited the chain transfer reactivity effectively to control the molecular weight of PMMA without decreasing of the polymer yield and the stereoregularity. As a result of this chain transfer polymerization, thermal and optical propertics of the PMMA obtained were improved by the control of chain end groups or by reducing a large amount of the samarium initiator.

22. High Molecular Weight Monodisperse Polymers Synthesized by Rare Earth Metal Complexes

Abstract High molecular weight polyethylene ( M n > 300,000, M w / M n = 1.6) was obtained by using bulky Sm(II) or Sm(III) species such as Me 2 Si(2-SiMe 3 -4-tBu-C 5 H 2 ) 2 Sm(THF) and Me 2 Si[2(3),4-(SiMe 3 ) 2 -C 5 H 2 ] 2 SmCH(SiMe 3 ) 2 as initiator. These complexes also conduct the polymerization of 1-pentene and 1-hexene to give isotactic polymers of M n > 20,000 with M w / M n = 1.6. By contrast the polar monomers such as methyl methacrylate and alkyl acrylates also proceeded the living polymerization by using Ln(C 5 Me 5 ) 2 R (R = H, Me) to give high molecular weight polymers ( M n > 450,000) with extremely low polydispersity ( M w / M n