The antibacterial monomer, 2,4,4'-trichloro-2'-acryloyloxydiphenyl ether (AcDP) was synthesized from 2,4,4'-trichloro-2'-hydroxydiphenyl ether (DP) and acryloyl chloride in the presence of dry T H F at 20ยฐC. Copolymers of AcDP with acrylic acid [poly(AcDP-co-AA)] or 2-hydroxyethyl methacrylate [poly(AcDP-co-HEMA)] were synthesized using BPO as a thermal initiator at 70ยฐC. The synthesized poly(AcDP-co-AA) and poly(AcDP-co-HEMA) were identified by IR and 'H-NMR spectra. The monomer reactivity ratios, rl (AcDP) and rz (AA), determined by the Kelen-Tudos method, were 0.21 and 1.28, respectively. The number average molecular weights of poly(AcDP-co-AA) and poly(AcDP-co-HEMA) were 2400 and 3000, respectively. The glass transition temperatures of poly(AcDP-co-AA) and poly(AcDP-co-HEMA) were 87 and 50"C, respectively. The rate of hydrolysis decreased in the order of poly(AcDP-co-AA) > AcDP > poly(AcDP-co-HEMA) > poly(AcDP). The antibacterial activities of poly(AcDP-co-AA) and poly(AcDP-co-HEMA) were studied against Staphylococcus aureus by the shake flask test. The antibacterial activity of poly(AcDP-co-AA) was higher than that of poly(AcDP-co-HEMA). The trend of magnitude of the antibacterial activities for copolymers containing the AcDP unit was in agreement with that of the rate of hydrolysis for the copolymers.