ESR studies of C-60-modified poly(N-vinylcarbazole)

The paramagnetic electronic structure changes of C-60-modified PVK subjected to different pretreatment have been studied with a variety of ESR techniques. It is found that in the C-60-chemically modified PVK polymer, there are mainly two kinds of paramagnetic species, a narrow peak( g=2.0028, Delta H-pp=2.2 G) attributed to the interaction between C-60 and corresponding carbazyl, and a the broad peak (Delta H-pp=11.2 G) which corresponds to the interaction between positively charged carbazyl and adjacent electron-rich carbazyl. Also, its temperature sensitivity is intriguing, and a transition state in which conformational equilibrium entropy is equal to zero at about 260 K might exist in the polymer. The effect of UV-irradiation on electronic structures of C-60-doped PVK and C-60-chemically modified PVK is discussed.