A tem study on polyoxymethylene rodlike crystals grown epitaxially on NaCl

Rodlike crystals of polyoxymethylene (POM) were isothermally grown onto the newly cleaved (001) face of NaCI from a 0.1 wt% solution in nitrobenzene and then were studied by transmission electron microscopy (TEM). Morphological observation in bright- and dark-field imaging modes and selected-area electron diffraction analysis directly evidenced that POM chain stems in the rodlike crystals are set parallel to the substrate surface and also perpendicular to the rod axis. That is, each of the rodlike crystals is an “edge-on” lamella of POM, the lateral face of which is in contact with the substrate surface. The contact plane of the edge-on lamella in question, namely, the crystallographic plane parallel to the substrate surface, is determined as the (100) plane of the hexagonal crystal lattice of POM.