Statistical thermodynamics of lattice polymer fluid

We obtain the partition function and the complete thermodynamic description for pure polymer fluids on a lattice model. The analytical expressions of thermodynamic quantities are presented in the present theory. The interaction dependence of partition function is included in our theory, which induces the interaction and temperature dependence of entropy. The overall entropy of the system has three fundamentally different types of contributions, i.e., the translational entropy, the configurational entropy and the thermal correction entropy. The second type contributes the main part, while the temperature and interaction energy dependence of entropy emerges from the third type contribution that is absent in Flory-Huggins theory and lattice fluid (LF) theory. The equation of state for pure polymer fluid is obtained and the parameters in it are determined. With the introduction of large coordination number approximate to the present theory, the LF theory is recovered. Compared with LF theory and experimental data, it has been demonstrated that the present theory is capable of adequately describing thermodynamic quantities of pure polymer fluids. (C) 2002 American Institute of Physics.