Study on the Transition of Amorphous PMMA by Using p-（Dimethylamino）Benzylidene Malononitrile as a Fluorescence Prpbe

In amorphous PMMA film, the fluorescence quantum yield of p-dimethylamino benzylidene malononitrile decreased with increasing temperture. Two break points in the φ_F vs. t plot occured at 105℃ and 45℃ , which correspond to the glass transition and β-transition of PMMA respectively. At the lower temperature there was a good linear correlation between lgφ_F and t. The result showed that the δ-transiton caused by methyl group motion occured within wide temperture range. The relationship between the nonradiative decay rate of the probe and the free volume of PMMA obtained by dilatometry was in accordance with the following equation k_nr=k_nr⁰exp（-v₀/bv_f） From our straight line, the intrinsic nonradiative decay rate (k_nr⁰) and the constant （b） of the probe were 5.71×10¹¹s^-1 and 1.94.