We previously found that a copolymer. poly(NIPAM-co-BP), consisting of N-isopropylacrylamide (NIPAM) and benzophenotle (BP) units, behaves as a photosensitizer showing temperature-controlled oxygenation activity by singlet oxygen (O-1(2)) in water (J. Am. Chem. Soc. 2006. 128 8751-8753). This polymer shows a heat-induced oxygenation enhancement at < 20 degrees C, while showing suppression at > 20 degrees C. This is driven by a heat-induced phase transition of the polymer from coil to micelle and then to globule state, controlling the stability and diffusion of 10, and the location of substrate. In the present work, effects of polymer concentration and BP content of the polymer oil the oxygenation activity were Studied at 5-35 degrees C. Increase in the polymer concentration leads to activity decrease at > 20 degrees C due to strong polymer aggregation, Suppressing incident light absorption of the BP units. With it decrease in BP content of the polymer, heat-induced oxygenation enhancement at < 20 degrees C is more pronounced because formation of small size micelles accelerates O-1(2), oxygenation. The obtained findings reveal that the polymer with low BP content, when used at high concentration. shows clear-cut off-on-off activity change against the temperature window: very low activity at < 5 degrees C and > 25 degrees C, and very high activity at middle temperature ranoe.