Theory of the epitaxial crystallization of polymers on alkali halide substrates. II. Polyoxymethylene and polythiomethylene

The epitactic behavior of a single chain of polyoxymethylene and of polythiomethylene on alkali halide substrates has been simulated by computing the coulombic, induced dipolar, and dispersion–repulsive potential energies as a function of polymer–substrate geometry. Inspection of the total potential energy surface for a polyoxymethylene chain in a 9/5 helix reveals a favorable alignment in which the chain is parallel to the substrate surface ((001) cleavage plane) with specific positioning along rows of positive charge. This preferential orientation has been found to be independent of lattice matching between the substrate and deposited phase. An identical mode of orientation is predicted for a polyoxymethylene chain and a polythiomethylene chain, both in the 2/1 cis‐planar conformation. The theoretical results for polyoxymethylene are in agreement with available experimental evidence, whereas the outcomes of the calculations performed on polythiomethylene should be considered predictive study to be complemented by a future experimental investigation.