Res. Chem. Intermed.
, Vol. 27, No. 7,8, pp. 823–835 (2001)
Ion recombination in PMMA doped with pyrene as
observed by wavelength selected radiothermoluminescence
and J. MAYER
Institute of Applied Radiation Chemistry, Technical University, Wróblewskiego 15,
93-590 ód´z, Poland
Abstract—Radioluminescence from electron-irradiatedpoly(methyl methacrylate),PMMA, pure and
doped with pyrene (Py) was investigated in the temperature range of 77– 295 K. The spectra of
emission were recorded, and temperature dependences of radioluminescence intensities at chosen
wavelengths were examined using a novel wavelength-selected radiothermoluminescence(WS RTL)
technique. The correlation between the WS RTL peaks and matrix relaxation temperatures were
found. The experimental results were explained in terms of solute radical ion recombination leading
to the Py monomer and excimer uorescence. The luminescence results were correlated with the
decay of Py ions as observed by spectrophotometric absorption method.
Poly(methyl methacrylate), (PMMA) is one of the most popular and widely-used
polymers, but the identi cation of the radical ionic intermediates and their reactions
in irradiated PMMA have been a matter of dispute for a long time. Torikai et al.
[1– 5] studied ESR and absorption spectra of
-irradiated solid PMMA at 77 K and
suggested that trapped electrons or PMMA anions were produced in the polymer.
These results showed that the absorption band at 440 nm in
at 77 K can be assigned to an anionic species. Ionic intermediates generated
in PMMA lms were investigated by Tabata et al.  using nanosecond pulse
radiolysis technique at various temperatures, and by ESR after
-irradiation at 77 K.
Short-lived transients with optical absorption at 440 nm and 725 nm were observed
and assigned to cations and anions of PMMA, respectively. It is clearly seen that
the assignments of the absorption bands by these two groups are not consistent with
To whom correspondence should be addressed.