Facile synthesis and characterization of biodegradable antimicrobial poly(ester-carbonate)

Biodegradable antimicrobial poly(ester-carbonate)s were prepared facilely via a simple two-step process with low cost. First, poly(5,5-dibromomethyl trimethylene carbonate-co-epsilon-caprolactone) (PDBTCL) with pendant bromo groups was synthesized by the direct ring-opening copolymerization of 5,5-dibromomethyl trimethylene carbonate (DBTC) and epsilon-caprolactone (CL) in the presence of stannous octanoate (Sn(Oct)(2)) as catalyst. Then, the quaternization reaction between PDBTCL and a series of N,N-dimethyl alkylamines was performed under mild conditions, resulting in biodegradable poly(ester-carbonate) s with pendant ammonium salts (QPDBTCL). The chemical structure and composition of QPDBTCLs were characterized by H-1 NMR. The influences of alkyl chain length and charge density on the antimicrobial activity of QPDBTCLs against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were evaluated by OD600 and zone of inhibition methods. It was observed that QPDBTCLs with long alkyl chain on the ammonium groups exhibit significantly higher antimicrobial activity than those with short alkyl chain for both Gram-negative and Gram-positive bacteria. QPDBTCL with quaternary N,N-dimethyldodecylammonium groups shows strong antimicrobial activity even with very low charge density (4.3 mol%). This kind of biodegradable antimicrobial material may have potential applications as biomaterials.