CAST POLY(VINYL ALCOHOL) FILMS CONTAINING STACKS OF IMIDE ANION-RADICALS - CORRELATION OF SPECTRA AND CONDUCTIVITY

Aqueous solutions of naphthalene diimides, sodium dithionite reductant, and poly(vinyl alcohol) (PVA) were used to cast air stable n-doped films containing naphthalene diimide anion radicals in PVA. Both monomeric and oligomeric diimides, substituted with ionic phenyl sulfonate, propylammonium, or N-methylpyridinium groups, were employed. The loading of the film with anion radicals was varied as was the degree of reduction, Optical microscopy on the films showed no microcrystals of conductor, and samples with high conductivity appeared homogeneous, Characterization by vis, NIR, IR, and ESR spctroscopies showed that the anion radicals were present as pi-stacks. Films formed from monomeric diimides had the stacks preferentially oriented in the film plane, Oligomers gave isotropic films, In the film plane, four-probe conductivities were in the range 10(-3)-10(-2) S cm(-1) for films loaded with 5 wt % of diimide anion radicals, Spectroscopic and conductivity evidence for mixed valence stacks was found, The ratio of in-plane to across-the-plane conductivity ranged from 1 for spectroscopically isotropic samples to 10(5) for a mixed valence film from a monomeric diimide, Changes in the conductivity with diimide structure, loading, and extent of reduction were correlated with changes in the NIR and ESR spectra and are interpreted in terms of stack structure, stack anisotropy, and network formation.