Intramolecular Contributions to the Entropy and Energy of Fusion of Polyethyleneoxalate and Polyethylenesuccinate

摘要

The intramolecular or conformational contribution to the entropy and energy of fusion of polyethyleneoxalate (PEO) and polyethylenesuccinate (PES) are calculated in the rotational isomeric state approximation. Both aliphatic polyesters are found to have conformational entropies equal to or in excess of those measured and calculated for the lower melting homologs polyethyleneadipate, polyethylenesuberate, and polyethylenesebacate. Consequently, it is concluded that PEO and PES melt at substantially higher temperatures than the higher members of the homologous series of polyesterslsqb;sngbnd;Osngbnd;lpar;CH2rpar;xsngbnd;Osngbnd;COsngbnd;lpar;CH2rpar;ysngbnd;COsngbnd;rsqb;h,primarily because of larger enthalpies of fusion. Furthermore, it is shown that the major contribution to the increased enthalpies of fusion for PEO and PES can be attributed to their possession of crystalline conformations of lower intramolecular or conformational energy.