THIN-FILM PROCESSING AND OPTICAL-PROPERTIES OF CONJUGATED RIGID-ROD POLYQUINOLINES FOR NONLINEAR OPTICAL APPLICATIONS

A structurally systematic series of 14 conjugated rigid-rod polyquinolines and polyanthrazolines of current interest as electronic and nonlinear optical materials have been prepared and solubilized in organic solvents by complexation and processed into thin films of high optical quality, and their optical properties characterized. The high molecular weight polyquinolines were solubilized in high concentrations by reversible complexation with either diaryl phosphates, dialkyl phosphates, or metal halide Lewis acids in organic solvents to produce viscous solutions processable to thin films, coatings, and fibers by conventional techniques. Thin film coatings on substrates and free standing films in frames suitable for the characterization of various solid-state properties were prepared from the soluble polyquinoline complexes. The optical properties, especially optical absorption spectra and refractive indexes, were characterized and related to the systematic variation in structure. The lowest energy absorption band maximum in the optical spectra of thin films of the polyquinolines was in the range 370-448 nm, and the corresponding optical bandgap was found to be in the range 2.5-3.0 eV. The phosphate and Lewis acid complexes of the polyquinolines II and III were found to exhibit greater degrees of pi-electron delocalization than the pure polymers as evidenced by the larger lambda(max) of their lowest energy optical absorption band (389-547 nm). The intrinsic optical loss-alpha of the conjugated polyquinolines was found to be of the order 1-10 cm-1 in the transparent region (800-1900 nm) of the materials. These results on the thin-film processing of the conjugated polyquinolines from their soluble complexes will make possible detailed investigation of their electronic, photoconductive, and nonlinear optical properties as well as their potential applications.