Photocontrolled living anionic polymerization of phosphorus-bridged [l]ferrocenophanes: A route to well-defined polyferrocenylphosphine (PFP) homopolymers and block copolymers

Phosphorus-bridged strained [1]ferrocenophanes [Fe{(η-C ₅H₄)₂P(CH₂CMe₃))] (2) and [Fe((η-C₅H₄)₂P(CH₂SiMe ₃)]] (3) with neopentyl and (trimethylsilyl)methyl substituents on phosphorus, respectively, have been synthesized and characterized. Photocontrolled living anionic ring-opening polymerization (ROP) of the known phosphorus-bridged [l]ferrocenophane [Fe{(η-C₅H₄) ₂P(CMe₃)}] (1) and the new monomers 2 and 3, initiated by Na[C₅H₅] in THF at 5°C, yielded welldefined polyferrocenylphosphines (PFPs), [Fe{(η-C₅H₄) ₂PR}]., (R=CMe₃ (4), CH₂CMe₃ (5), and CH₂SiMe₃ (6)), with controlled molecular weights (up to ca. 60x10³ Da) and narrow molecular weight distributions. The PFPs 4-6 were characterized by multinuclear NMR spectroscopy, DSC, and by GPC analysis of the corresponding poly(ferrocenylphosphine sulfides) obtained by sulfurization of the phosphorus(III) centers. The living nature of the photocontrolled anionic ROP allowed the synthesis of well-defined all-organometallic PFP-b-PFS_F (7a and 7b) (PFS_F = polyferrocenylmethyl(3,3,3,-trifluoropropyl)silane) diblock copolymers through sequential monomer addition. TEM studies of the thin films of the diblock copolymer 7 b showed microphase separation to form cylindrical PFSF domains in a PFP matrix.