Experimentally- and theoretically-evaluated ultimate 3-dimensional elastic constants of trans-1,4-polyisoprene α and β crystalline forms on the basis of the newly-refined crystal structure information

The ultimate 3-dimensional elastic constants and compliance tensors have been evaluated for trans-1,4-polyisoprene (Gutta percha) α and β crystalline forms experimentally and theoretically. The theoretical estimation was performed by the molecular mechanics method on the basis of the newly-refined atomic coordinates obtained by quantitative analysis of the crystal structures using many numbers of X-ray reflections from the highly-oriented and highly-pure α and β crystalline samples. The calculated Young's modulus along the chain axis was 85.8 GPa for the α form and 72.3 GPa for the β form, in good agreement with the experimentally-obtained X-ray crystallite moduli, 72.4 GPa and 61.4 GPa, respectively.