Epitaxial crystallization of polyoxymethylene

Epitaxial growth of synthetic polymers on alkali-halide surfaces usually proceeds along the preferred 〈110〉 directions parallel to the {100} plane of the substrate. Polyoxymethylene was epitaxially crystallized as thin films on alkali halides and analyzed using the electron microscope. The metastable orthorhombic crystal form was obtained on substrates which exhibited a lattice match with the [100] distance of the orthorhombic form. Matching was not necessary for the growth of the normal hexagonal crystal form, although it did affect both the nucleation process and the growth rate of the epitaxial crystallization. The technique seems to be quite generally applicale in affecting the general morphology of the crystallization and the formation of metastable polymeric forms.