Synthesis of Polymeric Temperature Sensor Based on Photophysical Property of Fullerene and Thermal Sensitivity of Poly(N-isopropylacrylamide)

Two types of temperature sensor which have pyrene (Pyr) and fullerene (C60) attached to poly(N-isopropylacrylamide) (PNIPAM) are synthesized, and their thermal sensitivities are examined in terms of the fluorescence quenching efficiency of C60: One is pyrene-poly(N-isopropylacrylamide)-fullerene (Pyr-PNIPAM-C60) which has Pyr and C60 attached to each chain end of PNIPAM, and the other is pyrene-poly(N-isopropylacrylamide-co-fullerenylethyl methacrylate) (Pyr-P(NIPAM-co-C60)) which has Pyr attached to one chain end of PNIAPM and two C60s attached onto PNIPAM backbone. Both of them exhibit the same conformational change from coil to globule at a specific temperature, which results in drastic on-and-off quenching efficiency. The quenching efficiency of Pyr-P(NIPAM-co-C60) is larger than Pyr-PNIPAM-C60, since Pyr-P(NIPAN-co-C60) has more C60s located closer to Pyr than Pyr-PNIPAM-C60. These C60-based thermosensitive polymers exhibit well-defined on-and-off behavior at a small change in temperature.