A Molecular Dynamics Study on the Miscibility of Polyglycolide with Different Polymers

Abstract

The miscibility of mixtures between polyglycolide and the following polymers: polyethylene, polystyrene, polyacrylonitrile and polylactide is studied by Molecular Dynamics Simulation using Forcite and Blends Modules. The simulations of the binary mixture for the evaluation of the energy is achieved in the framework of the Flory-Huggins model. The Flory-Huggins interaction parameter, the mixing energy and the phase diagrams are analyzed and found to be the main parameters and features controlling the miscibility process in the present computer simulations. The results of the simulation show that when the Flory-Huggins interaction parameter Chi to a value close to 1 of mixtures the polyglycolide / polylactide, polyglycolide / polyacrylonitrile, polyglycolide / polyethylene and polyglycolide / polystyrene are miscible at 50K, 230K, 238K and 378K respectively. The commonly-accepted miscibility criteria of the binary namely mixing when Chi is negative or positive but small and non-miscibility when Chi is positive and higher than 1 is used in the present analysis. This led to the evaluation of a mixing energy of 1.5kcal/mole. The phase diagrams of all the binary mixtures are similar and present one critical point. The miscibility of the binary mixtures at that critical point corresponds to an optimal mole fraction of 0.5 but for different temperature for each binary mixture. In fine, the polyglycolide is miscible with polylactide for all the temperature range and above 378K for polyacrylonitrile, polyethylene and polystyrene. The results obtained are in agreement with those found in the literature.