Temperature Perturbation to Intrinsic Fluorescence of Phenyl Multimers in Glassy Polystyrene

The newly discovered fluorescence in polystyrene is used as a probe to understand the phenyl motions in glassy polystyrene fine particles when temperature increases from room temperature to 62°C. The large changes in fluorescence profiles (intensities and shapes) suggest profound phenyl motions and reorientations under 62°C. When excite a single phenyl ring (λex = 260 nm), proposed phenyl dimers (λex = 277 nm and 296 nm), and proposed tetramers (λex = 360 nm and 380 nm), the heating has negative effects on the fluorescence intensities of all emissions, while the heating exhibits positive effects on the fluorescence emissions when excite proposed trimers (λex = 325 nm and 340 nm). This implies that the phenyl motions and reorientations under 62°C in the studied time frame are in the direction of favoring the formations of proposed phenyl trimers, at the cost of proposed phenyl dimers and tetramers. With continuous heating under 62 °C, the emissions at λex = 277 nm showed different responses to the heat in its shorter wavelength region (350-367 nm) from its longer wavelength regions (374-426 nm), which is believed to be caused by the larger and increasing contributions of emissions from excited trimers (λex=340 nm) to the emissions at its longer wavelength side, through either indirect excitation of phenyl trimers by energy transfer or formation of excited trimers from some excited dimers, or both.