PHOTOCONDUCTIVITY AND PARAMAGNETISM OF FULLERENE CHEMICALLY-MODIFIED POLYMERS

Addition of the C-60 moiety, a powerful electron acceptor, to iodinate d poly(N-vinylcarbazole) (PVKI) by chemical reaction modifies consider ably the photoconductive property of PVKI. The photoinduced discharge rates for pure PVK, PVKI, C-60-chemically modified PVKI (C-60-PVKI cop olymer), and C-60-doped PVKI (a simple mixture of the component) under the same experimental conditions are found in the following order: C- 60-PVKI copolymer > C-60-doped PVKI > PVKI > PVK. The fullerenated PVK I has a visibly brownish yellow cast when compared with the unreacted polymer. The UV-vis absorption spectrum in which the main bands occur at 220, 230, 252, 268, 300, 332, and 346 nm extends the active range f rom about 300 to 860 nm. Also, its apparent temperature sensitivity is very intriguing, and an unusual temperature dependence for the ESR sp ectrum is observed. The photoconductive performance of the fullerenate d polymer is closely related to its paramagnetism. A considerable diff erence of electronic structure between pure PVKI and the C-60-PVKI cop olymer is indicated. (C) 1996 John Wiley & Sons, Inc.