Sorption isotherms for spherical penetrants in facilitating polymeric media using Monte Carlo simulations

Grand canonical ensemble Monte Carlo simulations of penetrant sorption in polymeric media have been used to predict sorption isotherms as a function of polymer–penetrant interactions. The polymer is modelled as a collection of hard chains and as a collection of square-well chains, while the penetrant is modelled as hard spheres and as square-well spheres. Partition coefficients have been compared for the different potentials of interaction for stationary and moving polymeric media. Partition coefficients are found to increase with increasing reservoir penetrant pressure and to be higher in moving polymeric media than in stationary polymeric media. Partitioning was studied also as a function of concentration of facilitating sites which have an increased affinity for penetrants. Partition coefficients increased with increasing concentration of facilitating sites. The presence of a second penetrant species of normal affinity is found to affect the partitioning of species with a special affinity for facilitating sites. The partition coefficient for the penetrant species with special affinity for facilitating sites is lower in a mixture than when present as the only component. The partition coefficient of the penetrant species of normal affinity at intermediate mole fractions is higher in a mixture than when present as the only component.