ABSTRACT
The entropy of the liquid state is positive relative to that of the amorphous polymeric state because liquid molecules are free to translate and rotate in a random manner, whereas polymer molecules have little freedom for either translation or rotation, and even segmental motion is limited. The polymers that have the greatest similarities with liquids are those in the rubbery amorphous state and above their glass transition temperatures at ambient temperature. Other amorphous polymers have higher glass transition temperatures and are in the glassy state at room temperature. Some polymers are observed in both amorphous and crystalline states that differ substantially in their densities or molar volumes. An important advance in the development of an understanding of polymer-liquid systems was the formulation of a corresponding polymer solution concept, a hypothetical reference solution with which real polymer solutions may be compared. The Flory-Huggins theory is useful in considering the thermodynamics of dilute polymer solutions.
