Open vessel photo-atom transfer radical copolymerization of benzyl methacrylate and vinyl ferrocene: Reactivity ratio determination

In this study, redox-active poly(benzyl methacrylate-co-vinyl ferrocene) copolymers were synthesized by photoinitiated atom transfer radical polymerization (Photo-ATRP) under open-vessel conditions. The monomer benzyl methacrylate (BzMA) was copolymerized with the monomer Vinyl ferrocene (VFc) at six different molar feed ratios varying from 85:15 to 10:90 (BzMA:VFc). The resulting copolymers were well characterized by 1H NMR spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy and UV-Vis absorbance spectroscopy, which collectively showed the presence of both monomer units in the polymer chain. Monomer reactivity ratios were calculated using a combination of three different methods: the Fineman–Ross (FR) linearization, the Kelen–Tüdős (KT) normalized linearization and the Mayo–Lewis (ML) non-linear least-squares minimization. The most statistically relevant results, r1 = 1.10 (BzMA) and r2 = 0.16 (VFc) obtained by ML suggested a tendency. A slighthomopropagationpreference for BzMA and a strong cross-propagation tendency forVFc, and was calculated as r1×r2 = 0.176. The ferrocene/ferrocenium (Fc/Fc+) redox was well-defined and reversible, as found using cyclic voltammetry (CV) analysis, with an oxidation peak around +0.45 V and a reduction peak around −0.80 V vs Ag/AgCl. Thermal stability, as measured by weight loss, was acceptable up to 250-290 °C by thermal analysis using TGA-DSC, with a progressive decrease in glass transition temperature (Tg) and increased char formation with increasing VFc content due to the elevated presence of iron-containing residues. The present results show that photo-ATRP is a useful option for the preparation of well-defined ferrocene-functionalized copolymers that display a tunable composition, electrochemical activity, and thermal properties, which renders them attractive for electrochemical sensor preparation, redox responsiveness and uses in energy storage applications.