REFRACTIVE-INDEX AND NONLINEAR-OPTICAL PROPERTIES OF POLYANILINE DERIVATIVES

An investigation of the refractive index and third-order nonlinear opt ical susceptibility chi(3) of two polypernigraniline derivatives, poly (4,4'-diphenylimine methine) (PDPIM) and poly(4,4'-diphenylimine p-he ptyloxybenzylidene) (PDPIHB) reveals effects of molecular structure on the linear optical and nonlinear optical properties of conjugated pol ymers. The chi(3) (-3omega; omega, omega, omega) of PDPIM was found to decrease relative to polypemigraniline, reflecting the observed decre ase of the oscillator strength of the 2.2 eV absorption band when a me thine carbon replaces one of the nitrogen atoms of pernigraniline repe at unit. The alkoxyphenylene side group substitution at the methine ca rbon in PDPIHB, however, significantly enhances the nonlinear optical response of PDPIHB while reducing the refractive index compared to PDP IM and polypemigraniline. The present results suggest that structural changes in conjugated polymers can be made in such a way as to enhance the nonlinear optical properties while modulating the linear optical properties. (C) 1994 John Wiley & Sons, Inc.