Antimicrobial activities of polymeric quaternary ammonium salts from poly(glycidyl methacrylate)s Zhixiang Liang a , Mingran Zhu a , Ying-Wei Yang b * and Hui Gao a ** Amino poly(glycerol methacrylate)s (PGOHMAs) were synthesized from linear and 8-arm poly(glycidyl methacrylate)s (PGMAs) via ring opening reactions with methylethylamine (MEA), diethylamine, and dipropylamine, respectively, which were further modified by quaternization reaction using methyl iodide to obtain quaternized PGMAs (QPGMAs for short). The products were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, and thermogravimetric analysis. The amination percentage of amino PGOHMAs and the degree of quaternization of QPGMAs were calculated by elemental analysis and X-ray photoelectron spectroscopy, respectively. According to the solubility test results, 8-arm PGOHMA modified with MEA (S8-MEA) is the only water-soluble derivative of amino PGOHMAs and was employed as a positive control for the comparison with QPGMAs. Antimicrobial studies on these PGMA derivatives were carried out by testing the minimum inhibitory concentration and the bacteria inhibitive rate against Escherichia coli and Staphylococcus aureus. The results indicated that QPGMAs possessed higher antimicrobial activity than S8-MEA and exhibited increased antimicrobial activity against both bacteria with an increased degree of quaternization in weak basic conditions. Moreover, the chemical structure of PGMA derivatives and pH value of the assay conditions were found to affect the antimicrobial activity. Copyright © 2013 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this paper. Keywords: synthesis; poly(glycidyl methacrylate); QPGMA; quaternization reaction; antibacterial activity INTRODUCTION Over the past decades, the risk of bacterial infection has been rising to be a global concern. [1] Misusing of antibiotics has been observed for many years, leading to an increased antibiotic resistance of bacterial pathogens in hospitals and communities, both in gram-negative and gram-positive bacteria. [2–5] Therefore, significant efforts have been made by many scientists to improve the efficacy and antimicrobial spectrum of existing drugs. [6–8] At present, the most commonly used antimicrobial reagents mainly include four broad categories [9–11] : (i) the oxidants, such as peroxides; (ii) the electrophilic agents, such as copper and mercury; (iii) organic biocides, such as formaldehyde; and (iv) cationic active biocides, such as chlorhexidine and quaternary ammonium compounds. However, these small molecules were highly toxic to the environment, and their protection was short-lived because of the difficulty in controlling the diffusion rate. [12] During the last two decades, continuous effort has been made to develop new antimicrobial polymers that are generally nonvolatile, chemically stable, and do not permeate through the skin of human body. [13–18] Although hundreds of polymeric compounds have been prepared, few of them were of visible antimicrobial activities. [19] Recently, much attention has been paid to quaternary ammonium compounds, which are very attractive for their antimicrobial applications because they target primarily at the microbial membrane and accumulate in cells driven by the potential of cell membrane. [20] Many researches have employed quaternary ammonium salts as biocides, owing to their low toxicity and a wide range of antimicrobial spectrum. [21,22] Tomiki and Shigeo [23] investigated the antimicrobial activity of polymeric quaternary ammonium salts and found out that the polymeric salts were more active than the corresponding monomer with the longest alkyl chain. Water-soluble quaternary ammonium salts of chitosan derivatives with a high charge density have been described to have a significant antimicrobial activity. [24,25] Polyurethane cationomers, polymerized from base polyurethane with chain extenders having a quaternary ammonium group, have been electrospun into nonwoven nanofibermats for antimicrobial nanofilter applications. [26] The antimicrobial ability of natural polysaccharides can also be improved by quaternization, as reported by Badawy and Kim et al. [27,28] As a highly versatile polymeric building block for postpolymerization modi fications of polymers, [29] poly(glycidyl methacrylate)s (PGMAs) * Correspondence to: Ying-Wei Yang, State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China. E-mail: ywyang@jlu.edu.cn ** Correspondence to: Hui Gao, School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300384, China. E-mail: ghhigher@hotmail.com a Z. Liang, M. Zhu, H. Gao School of Chemistry and Chemical Engineering, Tianjin University of Technol- ogy, Tianjin 300384, China b Y.-W. Yang State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, China Research article Received: 6 July 2013, Revised: 26 August 2013, Accepted: 23 September 2013, Published online in Wiley Online Library: 4 November 2013 (wileyonlinelibrary.com) DOI: 10.1002/pat.3212 Polym. Adv. Technol. 2014, 25 117–122 Copyright © 2013 John Wiley & Sons, Ltd. 117