Opto-acoustic study of tinuvin-P and rhodamine 6G in solid polymeric matrices

Laser-induced opto-acoustic calorimetry has been used to examine the thermo -elastic properties of two polymer matrices doped with tinuvin-P and the ra diation-less decay processes of rhodamine 6G (Rh6G) in them. The matrices a ssayed were methyl methacrylate (MMA) homopolymers P(MMA), and methyl metha crylate and 2-hydroxyethyl methacrylate (HEMA) copolymers P(MMA : HEMA). A slight difference in the thermo-elastic properties of the polymers, namely their adiabatic expansion coefficients, has been detected and found to corr elate with the long-term stability of the laser material. This suggests a k ey role of the heat-dissipation processes in the photostability of these po lymeric materials. On the other hand, the fluorescence quantum yield of Rh6 G is shown to vary with the polymer-matrix composition in a way consistent with its lasing efficiency. The Rh6G absorption and fluorescence quantum yi eld also change dramatically upon increasing its concentration, which sugge sts the co-existence of different Rh6G forms with different photophysical p roperties.