Characterization and analysis of defects in extruded/coagulated films of heterocyclic aromatic polymers for nonlinear optics studies

Abstract

AbstractThe high degree of electron delocalization in heterocyclic aromatic molecules makes this class of chemistry ideal for hyperpolarizability and NLO (nonlinear optics) polymer developments. This type of polymer is usually insoluble in common solvents and is not amenable to common optical film processing techniques like spin coating. A study of the approach in using an acidic solution extrusion followed by coagulation for optical quality film forming is reported in this paper. The polymers studied are: PBZT, (poly (p‐phenylene benzobisthiazole)); 6F‐PBO (polybenzobisoxazole containing hexaflorinated moities); and Zytel 330 (an amorphous nylon). Some of the resulting films showed an improved optical quality while others showed an extremely poor optical quality over the films used in a previous study. The optically clear films, however, were not of wave‐guiding quality. The defects in the films that would cause light scattering were characterized and the probable causes of these defects were discussed. The defects were: (a) optically inferior morphology, (b) micro‐voids, (c) macro‐voids, (d) solid particles, (e) lines in the transverse direction, and (f) lines in the machine direction. Identification and classification of these defects will help additional efforts in the future for improving the optical quality of heterocyclic aromatic polymer films.