Theoretical and Predictive Modelling of Physical Properties of Polymers

Abstract

The application of Boltzmann statistics to a complete distribution of molecular conformation energies of simplified homo- and copolymer models gives meaningful information about temperatures at which phase transitions take place in the bulk. We have calculated in the conformation statistical distribution (CSD) approximation Helmholtz free energy variation versus temperature δF = δU-TδS. where U and S are, respectively, the internal molecular energy and the Gibbs statistical entropy of the considered polymeric model. The deepest minima correspond to glass-transition temperature (T g ) and melting temperature (T m ) of modelled polymers, while the remaining peaks are relied to some other transitions, the existence of which is also experimentally proven. The adopted method is able to give T g and T m as a function of the molecular weight of polymers. Some indications can also be achieved about the instability of polymers. The same procedure has been applied to copolymers and blends and has given acceptable results for T g and T m as functions of the material microstructure and composition. Other thermal and mechanical properties, such as moduli, mobilities, chemical resistance to oxidation, physical tendency to miscibility, have been directly or indirectly estmated.