Antibacterial hydrogels containing quaternary ammonium (QA) groups were prepared via a facile thiol-ene click reaction using multifunctional poly(ethylene glycol) (PEG). The multifunctional PEG polymers were prepared by an epoxy-amine ring opening reaction. The chemical and physical properties of the hydrogels could be tuned with different crosslinking structures and crosslinking densities. The antibacterial hydrogel structures prepared from PEG Pendant QA were less well-defined than those from PEG Chain-End QA. Furthermore, functionalization of the PEG-type hydrogels with QA groups produced strong antibacterial abilities against Staphylococcus aureus, and therefore has the potential to be used as an anti-infective material for biomedical devices. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 656-667