A novel antibacterial piperazine derivative (PE-B) has been prepared via the nucleophilic substitution reaction of poly(ethylenediaminetetraacetic dianhydride-co-piperazine) (PE) with n-butyl bromide. PE was synthesized by a condensation polymerization reaction of ethylenediaminetetraacetic dianhydride (EDTAD) and piperazine (PA). The thermoresponsive test results showed that the PE was thermoresponsive; however, when it was quaternized by n-butyl bromide, this performance disappeared. The antibacterial test results showed that both the PE and PE-B exhibited potent inhibitory activity on S. aureus and E. coli. Specifically, PE had better antibacterial ability against S. aureus, but PE-B showed similar antibacterial activity against S. aureus and E. coli.