Transition Metal-Based Polymers with Controlled Architectures: Well-Defined Poly(ferrocenylsilane) Homopolymers and Multiblock Copolymers via the Living Anionic Ring-Opening Polymerization of Silicon-Bridged [1]Ferrocenophanes

Abstract

The living anionic ring-opening polymerization (ROP) of the methylated silicon-bridged [1]ferrocenophane Fe(η-C 5 H 4 ) 2 SiMe 2 1 initiated by n -BuLi, PhLi, FcLi (Fc = Fe(η-C 5 H 4 )(η-C 5 H 5 )), and 1,1‘-dilithioferrocene, fcLi 2 · 2 / 3 TMEDA (fc = Fe(η-C 5 H 4 ) 2 ) in THF at 20 °C has allowed the preparation of well-defined poly(ferrocenyldimethylsilanes) [Fe(η-C 5 H 4 ) 2 SiMe 2 ] n 4 with control of molecular weights, narrow polydispersities, and controlled end-group structures. The living anionic ROP of 1 has also been used to prepare a variety of novel, well-defined organometallic/organic/inorganic multiblock copolymers constructed from a combination of poly(ferrocenyldimethylsilane) (PFS), polystyrene (PS), and poly(dimethylsiloxane) (PDMS). The materials prepared included PFS-b-PDMS diblock copolymers ( 7a and 7b ), PDMS-b-PFS-b-PDMS triblock copolymers ( 8a and 8b ), a PS-b-PFS diblock copolymer ( 10a ), a PS-b-PFS-b-PDMS triblock copolymer ( 11 ), a PS-b-PFS-b-PDMS-b-PFS-b-PS pentablock copolymer ( 12 ), a PFS-b-PS-b-PFS triblock copolymer ( 15 ), and a PDMS-b-PFS-b-PS-b-PFS-b-PDMS pentablock copolymer ( 16 ). These materials were studied by cyclic voltammetry which afforded two reversible oxidation waves characteristic of redox-coupling arising from interactions between the skeletal iron atoms in the ferrocenylsilane blocks. The multiblock copolymers were also characterized by DSC which showed the presence of individual thermal transitions for each block which indicated that they were incompatible. In addition, the morphology of a film of PS-b-PFS ( 10a ) was investigated by TEM which showed a high degree of phase separation leading to the formation of microdomains of polystyrene and poly(ferrocenyldimethylsilane).