Triplet state energy and electron transfer in coronene-doped polymethylmethacrylate

The phosphorescence yield and decay kinetics of coronene in deoxygenated polymethylmethacrylate (PMMA) have been determined over the temperature range 77–300 K. At temperatures below ∼200 K the decays were close to single exponential (lifetime = 9.3 s at 77 K). However, at higher temperatures the decays were best fitted by the function I(t)=I0 exp(at+btn), where 0.3<n<0.4. This kinetic behaviour is attributed to long range energy transfer via a number of steps following a quasi-one-dimensional random walk from the coronene triplet state to trap sites. tinuities were observed in the temperature dependence of the phosphorescence yield of coronene in polymethylmethacrylate at temperatures of 175 and 255 K, corresponding to the onset of rotations within the polymer molecule.