Temperature-dependent, static, and dynamic fluorescence properties of disubstituted acetylene polymer films

The fluorescence thermosensing behavior of poly[1-(trimethylsilyl)phenyl-2- phenylacetylene] (PTMSDPA) as a thin film was investigated for the purpose of potential application of this polymer as a thermosensor. The fluorescence significantly decreased as the temperature increased in a wide range from 25 to 200°C. Conversely, the fluorescence increased as the temperature decreased. This fluorescence-temperature relationship held for the repeated trials. In the IR spectra, new peaks gradually appeared in a range from 1300 to 1800 cm ^-1 surrounding the 1590 cm^-1 peak due to C=C double bond. This was caused by increasing temperature, indicating an occurrence of a slight molecular perturbation in the main chain. In the time-resolved fluorescence spectroscopy, the fluorescence decayed as the temperature increased, indicating significant exciton deconfinement at high temperature. The quenching rates of PTMSDPA in solution and in film at 95°C are approximately 0.80 and 0.45, respectively. The PTMSDPA quenched the fluorescence more quickly than other fluorescent disubstituted acetylene polymers tested in this study. The PTMSDPA has a low density (0.91) and a high fractional free volume (FFV, 0.26). Thus, we presumed that PTMSDPA may provide substantial space for molecular perturbation even in the solid film.