Third-Order Nonlinear Optical Properties of a Series of Systematically Designed Conjugated Rigid-Rod Polyquinolines

Abstract

The third-order nonlinear optical properties of thin films of two series of conjugated rigid-rod polyquinolines, exemplified by poly(2, 2'-(l, 4-phenylene)-6, 6'-bis(4-phenyl quinoline)) (PPPQ, 2d) and poly(2, 7-(l, 4-phenylene)-4, 9-diphenyl-l, 6-anthrazoline) (PPDA, 3d), were investigated by third harmonic generation spectroscopy. Of the nine polyquinolines with diverse backbone structures, PPPQ has the largest optical nonlinearity with a χ(3) (-3ω; ω, ω, ω) value of 3.2 × 10−12 esu and 3.3 × 10−11 esu in the off-resonant and three-photon resonant regions, respectively. A comparison of the nonresonant χ(3) of the series of nine systematically derived polyquinolines showed that a scaling law of the form χ(3) ∼ (λmax)v ∼ Eg-v does not hold; in fact, the nonresonant χ(3) was essentially independent of the optical bandgap. These results suggest that structure-χ(3) propeny relationships in polymers cannot be inferred from those of oligomers and model compounds.

Electrochemical Properties and Electronic Structures of Conjugated Polyquinolines and Polyanthrazolines

“…We have extensively investigated the linear optical properties (optical absorption spectra, optical losses, dispersion of refractive index, etc. ), third-order nonlinear optical properties,and photoconductivity 6 of the conjugated polyquinolines and have found them to be very interesting and promising materials. However, to further improve the electronic, optoelectronic, and nonlinear optical properties of this class of polymers and establish the underlying structure−property relationships, we have synthesized a systematically designed series of new polyquinolines and polyanthrazolines …”