STATISTICAL THERMODYNAMICS IN THE FRAMEWORK OF THE LATTICE FLUID MODEL .1. POLYDISPERSE POLYMERS OF SPECIAL DISTRIBUTION

The Gibbs free energies and equations of state of polymers with specia l molar mass distributions, e.g., Flory distribution, uniform distribu tion and Schulz distribution, are derived based on a lattice fluid mod el. The influence of the polydispersity (or the chain length) on the c lose-packed mass density, the close-packed volume of a mer and the mer -mer interaction energy or the scaling temperature is discussed. The d iagrams of the Gibbs free energies as a function of temperature and ch ain length are simulated with a computer. The results suggest that a p olydisperse polymer is thermodynamically more stable than the correspo nding monodisperse polymer and that the thermodynamical properties of a polydisperse polymer are identical with those of the corresponding m onodisperse polymer when the average degree of polymerization is suffi ciently high.