Preparation of an Antibacterial Poly(ionic liquid) Graft Copolymer of Hydroxyethyl Cellulose

Poly­(ionic liquid)­s (P­(IL)­s) of different degrees of polymerization (10, 50, and 100) were prepared via RAFT polymerization using an alkyne-terminated xanthate as transfer agent, with a monomer conversion of up to ∼80% and a <i>Đ</i>_M of 1.5 for P­(IL)₁₀₀. Subsequently, P­(IL) chains were coupled to ¹⁵N-labeled azido-functionalized hydroxyethyl cellulose (HEC), forming graft copolymers of HEC with different chain length and graft densities, which were characterized using (¹³C and ¹⁵N) CP-MAS NMR and FT-IR spectroscopies. The antibacterial activities of HEC-<i>g</i>-P­(IL)­s were tested against Escherichia coli and Staphylococcus aureus and were comparable to ampicillin, a well-known antibiotic, demonstrating efficient activity of the graft copolymers against bacteria. Moreover, HEC-<i>g</i>-P­(IL)­s were slightly more effective against E. coli than S. aureus. A decrease in graft density of P­(IL)₁₀ on the HEC backbone decreased the activity of the graft copolymers against both bacteria. These findings suggest that HEC-<i>g</i>-P­(IL) could find applications as an antiseptic compound, for example, in paint formulation