Tailoring Effect of Alkyl Chain Length and Counter Anion on Antimicrobial Behavior of 4–Vinyl Pyridine–based Cationic Polymers

Polymers exhibiting anti–microbial properties constitute an important class of bioactive polymers whose properties can be easily tuned by simple polymer analogous reactions. Two series of new polymers were synthesized from 4–Vinyl pyridine, which was polymerized and quaternized in situ by using alkyl bromides of varying alkyl chain length. The well–characterized polymers were evaluated for their anti–microbial activity against a gram (–) bacterium (Citrobacter freundii) and fungus (Mucor circinelloides), and penicillin and fluconazole were the respective references. Polymer that exhibited the best activity was subjected to anion metathesis reactions as Br– was replaced with –OH, SO4 2, HSO3 –, NO3 – or CH3COO– to generate another series of new polymers. All the polymers exhibited strong antimicrobial activity against both the microbes studied. Polymer having butyl alkyl chain and –OH as counter ion exhibited the strongest activity with minimum inhibitory concentration of 60.0 μg/mL and 250 μg/mL, respectively, against the bacterium and fungus studied.