Calculation of the Intramolecular Contribution to the Entropy of Fusion in Crystalline Polymers

Abstract

The intramolecular contribution to the entropy of fusion of crystalline polymers is treated through calculation of the change in configurational entropy on melting of a single isolated polymer chain. Perfect backbone conformational order is assumed in the crystalline polymer chain, and the configurational entropy of the molten amorphous polymer chain is obtained through calculations based on the rotational isomeric state model of polymers. Comparison of the calculated change in intramolecular configurational entropy on melting with experimental results is achieved by assuming the entropy of fusion consists of two independent contributions: the entropy of fusion due to volume expansion (intermolecular contribution), and the entropy of fusion at constant volume, which is identified as the change in intramolecular configurational entropy. Several linear polymers are treated in the above fashion. The agreement between the calculated and experimentally determined intramolecular contribution to the entropy of fusion is generally satisfactory, and several conclusions are drawn based on this agreement.