On the calculation of molecular conformation in crystalline polymers

The stability of helical conformations in simple polymer chains should depend upon intramolecular interactions, which can be described in a first approximation in terms of repulsive forces between nonbonded atoms along the chain plus a small contribution from dispersion forces. Using the same consistent set of interaction parameters as in a previous work on small molecules, the conformational potential energy of isolated polymer chains satisfying the postulate of the conformational equivalence of each monomeric unit has been investigated as a continuous function of skeletal bond angles. The most stable conformations corresponding to the deepest minima of the potential energy plot for polyethylene, polytetrafluoroethylene, polyoxymethylene and polyethylene oxide are in good agreement with the conformations experimentally observed from X-ray diffraction patterns.