Bimetallic samarium(III) catalysts via electron transfer initiation: The facile synthesis of well-defined (meth)acrylate triblock copolymers

A method for generating a bifunctional organolanthanide(III) initiator in situ from a (meth)acrylate monomer and a divalent samarium precursor, (C5Me5)(2)Sm (I) or (C5Me5)(2)Sm(THF)(2), (2), is described. This process involves one-electron transfer from the Sm(II) species to monomer, forming radical anions which couple to give a bimetallic samarium(III) enolate that acts as a bisinitiator for living polymerization. Well-defined, highly syndiotactic ABA triblock copolymers containing both methacrylate and acrylate segments were prepared in two monomer addition steps with this methodology. Selective side chain deprotection may be carried out on copolymers containing poly(tert-butyl acrylate) or poly(benzyl methacrylate) blocks to give syndiotactic ester-acid copolymers. (C) 1997 Elsevier Science Ltd.