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 f ilms containing naphthalene diimide anion radicals in PVA. Both monome ric and oligomeric diimides, substituted with ionic phenyl sulfonate, propylammonium, or N-methylpyridinium groups, were employed. The loadi ng of the film with anion radicals was varied as was the degree of red uction, Optical microscopy on the films showed no microcrystals of con ductor, and samples with high conductivity appeared homogeneous, Chara cterization by vis, NIR, IR, and ESR spctroscopies showed that the ani on radicals were present as pi-stacks. Films formed from monomeric dii mides had the stacks preferentially oriented in the film plane, Oligom ers 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 fo r mixed valence stacks was found, The ratio of in-plane to across-the- plane conductivity ranged from 1 for spectroscopically isotropic sampl es to 10(5) for a mixed valence film from a monomeric diimide, Changes in the conductivity with diimide structure, loading, and extent of re duction were correlated with changes in the NIR and ESR spectra and ar e interpreted in terms of stack structure, stack anisotropy, and netwo rk formation.