A molecular model of the elastic behavior of polymethylene chains

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