Primary amine groups of branched poly(ethylene imine) (PEI) were functionalized with quaternary ammonium groups, alkyl chains of different length, allylic and benzylic groups in a one-step reaction, using a carbonate coupler. The structure of the obtained amphiphilic polymers was determined by means of H-1 and C-13 NMR spectroscopy. Depending on their hydrophilic/hydrophobic balance, the obtained polymers can be used as water-soluble disinfectants and for antimicrobial coating materials. The bactericidal properties of some of the amphiphilic polymers against Gram-negative and Gram-positive bacteria were investigated. Minimal inhibitory concentrations (log 4 reduction of bacterial growth) against Escherichia coli and Bacillus subtilis were determined in the range of 0.3-0.4 mg/mL and 0.03-0.04 mg/mL for water-soluble polymers. Glass slides coated with functionalized PEIs showed a reduction of colony forming units of at least 95%, at best 99.9%, against E. coli and B. subtilis.