Abstract
On the basis of the conformational entropy and enthalpy for unperturbed polyethylene terephthalate (PET) and nylon 6 computed with restricted or unrestricted rotation about the skeletal bond, the thermodynamic quantity RTQ, the free energy difference between the crystalline and quasi-crystalline regions, was evaluated for several non-isomorphic PET and nylon 6 copolymers. Good agreement with experimental results was obtained. From the change of RTQ with XA, mole fraction of major component, it is suggested that the rotation about skeletal bonds in the quasi-crystalline region (of major component) is more restricted with the increase of the content of minor component.
