Thermodynamic functions of both simple (monomeric) and polymeric melts: MFA approach and Monte Carlo simulation

Abstract

The influence of equilibrium polymerization on the thermodynamic properties of model systems consisting of building units with well-defined characteristics and interactions is investigated. The systems under study are thought to resemble more or less accurately undercooled melts, and the calculations performed give the configurational part of the thermodynamic functions of these melts. The whole investigation is performed by using two approaches. In the first one, the temperature courses of the entropies and the specific heat of the systems as well as the average flexibility and the mean chain length of the polymer molecules are obtained in the framework of a mean field approximation (MFA). In the second approach, the bulk characteristics and the configurational properties of the model systems are obtained by using Monte Carlo simulations (MCS). The correspondence and the differences between the thermodynamic properties for the same systems in the two approaches are analyzed and discussed. The model used in our MCS is a modified version of the so-called independent monomer state model proposed earliar by Jarič and Bennemann. The temperature course of the thermodynamic functions of the systems under investigation is analyzed and compared with existing experimental data. The existence of phase transition corresponding to melt-crystal or order-disorder transformation in the system is discussed based on the two approaches.