| Abstract: | A number of theoretical approaches to the problem of free volume in polymers are discussed. Because some questions in the Bueche approach remain unresolved, the lattice-gas model was studied. Inconsistencies in the independent-vacancy approximation led to consideration of a mean-field model and then a precise Padé-approximant solution, neither of which gave satisfactory agreement with experiment. Introduction of an internal pressure parameter to model the effects of the chainlike structure of polymers restores agreement with experiment. |
