EPR of mesoscale polyanilines

Electron paramagnetic resonance studies of the undoped and d,l-camphorsulfonic acid-doped tetra-, octa-, and hexadecamer of aniline are reported. Undoped oligomers have ~1 spin per 1000 2-ring repeats, increasing with oligomer length, that are suggested to originate from self-doping mechanisms. Doped oligomers have a temperature-independent Pauli susceptibility of ~40×10−6 emu/mole 2-ring repeats, showing the importance of three-dimensional delocalization. There is also a localized spin density of ~1 spin per twenty-five 2-ring repeats, and nearly Lorentzian lineshapes. Doped samples have 6 to 300 K FWHM linewidths decreasing from 10 to 4, 6 to 3.5, and 5 to 1.5 Gauss in the tetra-, octa-, and hexadecamer, respectively, implying increasing delocalization.