Synthesis and characterization of ferrocene end-capped poly([e]-caprolactone)s by a combination of ring-opening polymerization and aclicka chemistry techniques

Ferrocene (Fc) end-capped linear and star-shaped poly([e]-caprolactone)s (PCLs) with different numbers of arms were synthesized by a combination of ring-opening polymerization (ROP) and aclicka chemistry techniques in a four-step reaction procedure. In the first step, the polymer backbones were prepared via ROP of the [e]-caprolactone ([e]-CL) monomer in bulk by employing the compounds with different numbers of hydroxyl groups as the multisite initiators and stannous octoate (Sn(Oct)2) as the coordination-insertion catalyst. The hydroxyl end-groups of the obtained PCLs were then converted into a bromides and azides consecutively. In the final step, the Fc moiety was attached to the termini of the PCLs using a Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction between the azide end-groups of the PCLs and the acetylene group of ethynylferrocene under ambient conditions. In all cases, the FT-IR and 1H NMR spectra indicated a successful and quantitative transformation of the desired end-functional groups. The electrochemical properties of the Fc end-capped PCLs were also investigated via cyclic voltammetry (CV).