Dielectric Barrier Discharge Plasma Polymerization of N-Vinylimidazole: Structural Characterization and Cr3+ Coordination Behavior

Plasma polymerization offers a solvent-free route to functional polymer materials, but the structural integrity and accessibility of functional groups in plasma-derived networks remain insufficiently validated. Herein, N-vinylimidazole (NVI) was polymerized using atmospheric-pressure dielectric barrier discharge (DBD) plasma in a liquid-film configuration to generate a chemically heterogeneous poly(N-vinylimidazole)-like material that could be recovered and evaluated in aqueous solution. ATR–FTIR and 1H NMR spectroscopy indicate substantial vinyl-group consumption with retention of imidazole functionality. Functional behavior was probed using chromium(III) (Cr3+) as a model metal ion. UV–Vis spectroscopy revealed systematic changes in the Cr3+ d–d transition region (~580–600 nm) with increasing polymer concentration, consistent with ligand-field perturbation arising from interactions with imidazole donor sites. A monotonic increase in absorbance with an increasing ligand-to-metal ratio was observed, followed by plateau behavior at higher ratios, indicating saturation of accessible coordination environments. These results demonstrate that plasma-polymerized material retains chemically accessible imidazole functionalities capable of coordinating transition-metal ions in solution, establishing atmospheric-pressure plasma polymerization as a viable route to functional imidazole-containing materials.