| Abstract: | A series of essentially triblock poly(m-phenylene isophthalamide-b-ethylene oxide) with sequence PEO-(MPD-I)-PEO or (MPD-I)-PEO-(MPD-I) and their admixtures with (PEO)n were studied as solution cast films. Experimental techniques included transmission optical microscopy, transmission electron microscopy, electron diffraction, and X-ray diffraction. Characterization of these systems showed that structure could develop in two ways. The first way was the development of a typical polycrystalline structure of the (MPD-I) segment by the action of such agents as formic acid. In a second manner, however, a non-typical development was manifested by the appearance of crosses In the polarized opticial microscope. These samples showed only an amorphous halo when subjected to wide angle X-ray diffraction measuremfents. Their small angle pattern suggested scattering by dispersed particles. Other experiments indicated the crosses would form only under an unusually restrictive set of conditions, principally that the PEO present must be above a certain molecular weight and concentration and, furthermore, that the solvent must contain a salt such as LiCl. These observations led us to speculate that optical activity of the films showing crosses could occur either by chain orientation near the interface of a spherical particulate second phase or from stress induced bond polarization resulting from the film formation process. |
