A molecular model of the elastic behavior of polymethylene chains

In this paper, the elastic behavior of a polymethylene (PM) chain is investigated by using a realist rotational-isomeric-state (RIS) model. In our calculation, the non-local interactions between pairs of segments in polymethylene chain are also considered, and the Lennard-Jones (L-J) potential function is adopted Chain dimensions and thermodynamics statistical properties PM chains with various elongation ratios lambda are calculated. We find, that the elastic force increases slowly with elongation ratio for small lambda, and abruptly for large lambda. In the meantime, the energy contribution to elastic force, is negative and significant, especially for large lambda. Our calculations may provide some insight into the macroscopic phenomena of rubber elasticity.