In this study, we report on the safe and scalable N-methylation of primary amines in a linear polyglycerol backbone structure with altering molecular weight using gaseous chloromethane for the generation of quaternary ammonium groups. All polymers were subsequently analyzed for their antibacterial and antibiofilm properties against drug-resistant Staphylococcus aureus, showing that the implementation of quaternary ammonium groups to a polymer backbone structure is an efficient way to generate new antimicrobial agents. Thereby, the molecular weight of the polymer backbone structure strongly correlates to its antibacterial effect and can be altered depending on the desired application.