Computational Study of the Tensile and Compressive Properties of Ordered Polymers via the Austin Model 1 (AM1) Semi-Empirical Molecular Orbital Method

摘要

The Austin Model 1 (AM1) semi-empirical molecular orbital method has been used to calculate tensile moduli and molecular tensile and compressive deformations for several ordered polymers and a graphite model. The calculated moduli are an improvement over previous Modified Neglect of Differential Overlap (MNDO) calculations. These moduli are the ultimate moduli for the perfectly aligned bulk systems. By analyzing the deformation of polymer molecules in tension and compression, the failure modes and weak points in the molecules can be determined. In compression, all the heterocyclic rigid rod polymers exhibit a bending failure mode. In tension and compression, the phenyl group in the rods is deformed more easily than the heterocyclic moiety, thus causing a lowering of the modulus. The hypothetical ladder polymer, polyacene, shows more tensile and compressive resistance than any of the rods, suggesting that further study into ladder polymers is warranted. Polymers, Molecular orbital, Compressive properties, Tensile properties, Ordered polymers, Computational chemistry, Molecular modeling. (JES)