An Assessment of the Accuracy of Semi-Empirical Quantum Chemistry Calculations of the Mechanical Properties of Polymers
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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The ultimate mechanical properties of polymers, assuming perfect morphology, will be limited by the mechanical properties of a single, ideal polymer chain. Previous calculations of polymer chain moduli using semi- empirical SE quantum chemistry methods have resulted in modulus values much higher than experimentally measured. This study investigated the error in the calculated inherent to the method of calculation by comparing SE results for C-C bond potentials in two well characterized polymers, polyethylene and polydiacetylene. It was found that the SE calculation systematically overpredicted bond stiffness in these polymers by approximately 25 to 30. This is the upper limit on the modulus overprediction, depending on the importance of bond extensioncompression as compared to other deformation modes in the overall deformation of the polymer chain.
- Polymer Chemistry