Electron spin resonance of polyparaphenylene-based carbons

We report electron spin resonance (ESR) results on heat-treated polyparaphenylene (PPP) over the heat-treatment temperature (T-HT) range of 650-2900 degrees C. Two distinct spin centers are identified corresponding to a broad (similar to 5 G) ESR peak below T-HT=750 degrees C and a narrow (similar to 0.5 G) ESR peak above T-HT=650 degrees C. ESR peaks from both spin centers are observable for T-HT=700 degrees C, a material of particular interest for device applications. T-1 and T-2, the spin-lattice and spin-spin relaxation times, respectively, are estimated for both spin centers, and these results are discussed in relation to previously reported Raman spectroscopy and magnetic susceptibility measurements. (C) 1996 American Institute of Physics.