BODIPY-conjugated thermoresponsive copolymer as a fluorescent thermometer based on polymer microviscosity.

Research Center for Solar Energy Chemistry and Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka 560-8531, Japan.
Langmuir (Impact Factor: 4.38). 10/2009; 25(22):13176-82. DOI: 10.1021/la901860x
Source: PubMed

ABSTRACT A simple copolymer, poly(NIPAM-co-BODIPY), consisting of N-isopropylacrylamide (NIPAM) and boradiazaindacene (BODIPY) units, behaves as a fluorescent thermometer in water. The copolymer exhibits weak fluorescence at <23 degrees C, but the intensity increases with a rise in temperature up to 35 degrees C, enabling an accurate indication of the solution temperature at 23-35 degrees C. The heat-induced fluorescence enhancement is driven by an increase in the polymer microviscosity, associated with a phase transition of the polymer from the coil to globule state. The viscous domain formed inside the globule-state polymer suppresses the rotation of the meso-pyridinium group of the excited-state BODIPY units, resulting in heat-induced fluorescence enhancement. The polymer shows reversible fluorescence enhancement/quenching regardless of the heating/cooling process and displays high reusability with a simple recovery process.