Hyperbranched poly(ferrocenylphenylenes): Synthesis, characterization, redox activity, metal complexation, pyrolytic ceramization, and soft ferromagnetism

Hyperbranched poly(ferrocenylphenylenes) (hb-PFPs) with high molecular weights were synthesized by the copolycyclotrimerizations of (E,E)-1,1′-bis[2-(4-ethynylphenyl)vinyl]ferrocene (1) with (E)-1-[2-(4-ethynylphenyl)vinyl]ferrocene (2) catalyzed by TaCl ₅-Ph₄Sn at room temperature in high yields (up to 97%). Effects of reaction conditions, such as monomer and catalyst concentrations, reaction time and molar feed ratio (r_1/2), on the copolycyclotrimerization were investigated. Solubility of the copolymer is decreased with an increase in its content of diyne component (N ₁/N₂). The hb-PFPs were characterized by IR, NMR, UV, CV and TGA analyses. The copolymers are redox active, whose oxidation potentials are decreased with an increase in N₁/N₂. They are thermally stable, losing ∼5% of weights when heated to 384-400 °C and retaining ∼70% of weights when pyrolyzed at 1200 °C. The complexation with cobalt carbonyl further metallizes the hb-PFPs and the pyrolytic ceramization of the cobalt-polymer complexes yields soft ferromagnetic ceramics with high magnetizability (M_s up to ∼126 emu/g) and low coercivity (H_c down to ∼0.068 kOe).