ELECTRON-SPIN-RESONANCE OF POLYPARAPHENYLENE-BASED CARBONS

We report electron spin resonance (ESR) results on heat-treated polypa raphenylene (PPP) over the heat-treatment temperature (T-HT) range of 650-2900 degrees C. Two distinct spin centers are identified correspon ding 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 pe aks from both spin centers are observable for T-HT=700 degrees C, a ma terial of particular interest for device applications. T-1 and T-2, th e spin-lattice and spin-spin relaxation times, respectively, are estim ated for both spin centers, and these results are discussed in relatio n to previously reported Raman spectroscopy and magnetic susceptibilit y measurements. (C) 1996 American Institute of Physics.