PREDICTION OF POLYMER CRYSTAL-STRUCTURES AND PROPERTIES - POLYETHYLENE AND POLY(OXYMETHYLENE)

Molecular mechanics is used to calculate in a unified manner, from transferable conformational energy functions, the packing parameters and energy, vibrational dispersion curves, heat capacity, and thermodynamic functions, elastic constants, and refractive indices of polyethylene (PE) and poly(oxymethylene) (POM). PE was chosen as a 'standard' to illustrate the method and POM because it occurs in two crystal forms occasioned by the effect of packing forces in distorting the intramolecular torsion angles and because its crystal properties are of interest. Compared to the free multiplied by (times) multiplied by (times) GG multiplied by (times) multiplied by (times) the helix in the orthorhombic form is under compression and that in the hexagonal form under tension. Good agreement between calculated and experimental structures was found.