Thermosensitive and superabsorbent polymer hydrogels were synthesized by copolymerization of three kinds of tri-n-alkyl vinylbenzyl phosphonium chlorides (TRVB) with different lengths of alkyl chains, N-isopropylacrylamide (NIPAAm), and N,N'-methylenebisacrylamide (MBAAm). The water-absorption ability and antibacterial activity of the hydrogels against Staphylococcus aureus (S. aureus) were investigated. The water content of TRVB-NIPAAm-MBAAm copolymers decreased with increasing temperature and increased with increasing phosphonium groups in the copolymers, while it decreased with increasing chain length of the alkyl groups in the phosphonium groups as well as with an increasing degree of crosslinking in the copolymers. The TRVB-NIPAAm-MBAAm copolymers with a higher TRVB content in the copolymers exhibited higher antibacterial activity against S. aureus, but decreased with increasing chain length of alkyl groups in phosphonium groups. The TRVB-NIPAAm-MBAAm copolymers exhibited the highest antibacterial activity at 30 degreesC against S. aureus in deionized water.