Studies on the synthesis and antibacterial activities of polymeric quaternary ammonium salts from dimethylaminoethyl methacrylate

Four quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl chloride (BC), butyl bromide (BB), dodecyl bromide (DB) or hexadecyl bromide (HB), respectively. And then, the monomers were homopolymerized to obtain four polymeric quaternary ammonium materials with different lengths of alkyl chain, which were referred to as poly(DMAEMA-BC), poly(DMAEMA-BB), poly(DMAEMA-DB) and poly(DMAEMA-HB), respectively. The resultant monomers and related polymers were characterized by elemental analysis, FTIR, NMR, thermogravimetric analysis (TGA) and so on. Their bactericidal activities were evaluated by determining minimum bactericidal concentration (MBC) values and inhibitory zone diameters against Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli), respectively. The results showed that the MBC values of monomer DMAEMA-DB and DMAEMA-HB were 12-24 μg/mL against E. coli and S. aureus. However, the MBC values of monomer DMAEMA-BC and DMAEMA-BB were higher than 50 mg/mL against test microbe. It was very interesting that poly(DMAEMA-BC) and poly(DMAEMA-BB) exhibited greater bactericidal activities than their precursory monomers, but poly(DMAEMA-DB) and poly(DMAEMA-HB) present contrary results.