Elastic modulus of the crystalline phase of poly(cis 1,4‐isoprene)

Abstract
The crystalline elastic modulus of poly(cis 1,4‐isoprene) has been measured by x rays and calculated by molecular mechanics. The experimental modulus is E = (2.3 ± 0.3) × 109N m−2. The calculated modulus is E = (8.8 ± 0.1) × 109N m−2 for chains in S+ cis ST conformation and E = (6.1 ± 0.1) × 109N m−2 for chains in S+ cis S+T conformation. The modulus calculated for a statistical structure including both conformation is E = (6.7 ± 0.1) × 109N m−2. The experimental modulus is thought to be a lower limit because of partial crystallinity of the sample. The chief mechanism of deformation is rotation around single bonds adjacent to the double bond.