Photophysics of poly(2,3,4,5,6-pentafluorostyrene) film
The Journal of Physical Chemistry
6495 where the term containing AI accounts for the i = j contribution in the sum The averages in eqs A7 and A8 are defined by between the chemical potential of the mixture and a standard chemical potential, which we choose to be the chemical potential for xA = 0. Then the free energy difference of interest is where Thus, the second-order contribution is partly symmetric and partly antisymmetric under the operation of interchanging A and B. This could provide an explanation of the lack of
... the lack of symmetry in the experiment, if it were not for the universality of the compensation temperature within a compensation class. As has been explained in ref 1, compensation only occurs if one term dominates or if the temperature dependence of all dominating terms is the same. We do not see a physical reason for the temperature dependence of Ai to be the same as the temperature dependence of (&/an or of A. Therefore, the asymmetry of the experimental result cannot be explained as a second-order effect of interactions with the resin. The temperature-dependent steady-state emission, emission polarization anisotropy, and fluorescence kinetics of poly-(2,3,4,5,6-pentafluorostyrene) film are reported. Two interconverting excited-state conformations of the chromophore have been identified. The fluorescence of the higher energy conformation results from excitation on the red edge of the polymer absorption band at temperatures below 180 K. The energy barrier for conversion of the higher energy conformer to the lower energy conformer is estimated to be E/hc = 27 f 7 cm-'. Electronic energy migration is not evident in this polymer. 0022-365419Ol2094-6495%02.50/0 sorption is much like a monoalkyl-substituted benzene absorption. This observation is indicative of weak interaction in the ground (1) OConnor, D. 9.; Scott, G. W. Laser Studies of Energy Transfer in (32) Gupta, M. C.; Gupta, A.; Horowitz, J.; Kliger, D. Time-resolved fluorescence and emission depolarization studies of polystyrene: photochemical processes in polymeric systems. 9. Mucromolecules 1982, I S , 1372-76. (33) Putnam-deLavareille, N.; Geuskens, G. Luminescence studies of polymers-IX: polarization of the fluorescence of copolymer films. Eur. Pentasodium orthoperiodate, NaS129106, has been prepared for use as a source in 129Xe Mossbauer spectroscopy. Raman and Iz7I Mbsbauer spectroscopy, along with chemical analysis, were used to characterize the compound. The high recoil-free fraction and narrow line width, 7.2-7.3 mm/s, demonstrate the merits of Na5129106 compared to previously used sources. A high-yield preparation of the IBXe reference standard, &hydroquinone xenon clathrate, 3C6H4(OH)2.0.92Xe, is also described.