Complexation chemistry for tuning release from polymer coatings

The strategy of metal ion complexation is employed to design a delivery system for an antifouling agent (AFA) in marine paints. A poly(1-vinylimidazole-co-methyl methacrylate) copolymer (PVM), together with Cu²⁺ or Zn²⁺ formed a PVM-M²⁺ complex. The AFA, Medetomidine, was then coordinated into the complex. The coordination strength was investigated in solution by ¹H NMR and on solid surfaces by using the Quartz Crystal Microbalance with Dissipation monitoring technique (QCM-D) and Surface Plasmon Resonance (SPR). From the ¹H NMR experiments strong interactions were observed between Cu²⁺ and the PVM-polymer and between Medetomidine and the PVM-Cu²⁺ complex. From the QCM-D and SPR measurements it was shown that Cu²⁺, compared to Zn²⁺, exhibited a larger affinity for the PVM-copolymer surface that resulted in higher degree of swelling of the polymer film. Large amounts of Medetomidine were adsorbed to the PVM-Cu²⁺ complex resulting in low desorption rates. However, the adsorbed amount of Medetomidine was lower to the Zn²⁺ doped polymer and a higher desorption rate was observed. These results indicate the possibility of tuning the release of Medetomidine by altering the coordinating metal ion, which may prove to be favorable in a paint formulation.