Evolution of dielectric response in polyaniline

Summary form only given. We report the optical reflectance from thin films of polyaniline with camphor-sulfonic acid as a counter ion (PAN-CSA). The films, which are cast out of blends of chloroform and m-cresol, show a change in crystallinity and dc conductivity with increasing m-cresol content. /sup 1/ Kramers-Kronig analysis shows that the optical absorption increases in the far IR with increasing order. Comparison of these samples with the earlier non-stretched HCl doped materials shows that the real part of the dielectric function evolves from being postive to showing multiple zero crossings in PAN-CSA, becoming negative in the mid-IR, then positive again in the far IR. Microwave measurements show a negative dielectric constant for the more metallic of the PAN-CSA samples./sup 2/ Analysis of the energy loss function also shows a clear plasma resonance peak at ~1.1 eV, unlike non-stretched PAN-HCl materials. Additionally, the loss function shows stronger phonon peaks and higher loss in the least conducting samples. These results will also be compared to other PAN-CSA (m-cresol) optical data/sup 3/, and to stretched PAN-HCl materials and PAN-MSA (methyl sulfonic acid) cast from m-cresol, to discuss the key role of inhomogeneous disorder.