A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water within a Glassy Polyetherimide

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed us to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bonding established in the system on the dynamics of water mass transport.

A Molecular Interpretation of the Dynamics of Diffusive Mass Transport of Water Within a Glassy Polyetherimide

The diffusion process of water molecules within a polyetherimide (PEI) glassy matrix has been analyzed by combining the experimental analysis of water sorption kinetics performed by FTIR spectroscopy with theoretical information gathered from Molecular Dynamics simulations and with the expression of water chemical potential provided by a non-equilibrium lattice fluid model able to describe the thermodynamics of glassy polymers. This approach allowed to construct a convincing description of the diffusion mechanism of water in PEI providing molecular details of the process related to the effects of the cross- and self-hydrogen bondings established in the system on the dynamics of water mass transport.

Transport properties of lattice fluid with SALR-potential on a simple square lattice

The transport properties of the lattice fluid with the attraction interaction between the nearest and repulsion interaction between the next-next-nearest neighbours on the square lattice are investigated. Computer simulation by the Monte Carlo method of the diffusion process in the specified system has been realised. The jump and tracer diffusion coefficients were determined. The dependence of the diffusion coefficients versus the concentration of adparticles and the interaction parameter of the model is investigated. The activation energy of jump and tracer diffusion determined. The possibility of estimating the jump diffusion coefficient of the lattice fluid with competing interactions using the Zhdanov’s relation on the base of information on the equilibrium properties of the system and the diffusion coefficient of a Langmuir (non-interacting) lattice gas is shown. In the future, it is planned to use the obtained results to study transport processes in 3D lattice systems which is suitable for describing the processes of mass or charge transfer in the volumes of solids.

A priori predictions of type I and type V isotherms by the rigid adsorbent lattice fluid

Adsorbents exhibiting non type I adsorption behaviour are becoming increasingly more important in industrial applications, such as drying and gas separation. The ability to model these processes is essential in process optimisation and intensification, but requires an accurate description of the adsorption isotherms under a range of conditions. Here we describe how the Rigid Adsorbent Lattice Fluid is capable of a priori predictions both type I and type V adsorption behaviour in silicalite-1. The predictions are consistent with experimental observations for aliphatic (type I) and polar (type V) molecules in this hydrophobic material. Type V behaviour is related to molecular clustering and the paper discusses the model parameters governing the presence/absence of this behaviour in the predicted isotherms. It is found that both the solid porosity and the adsorbate interaction energy/energy density are deciding factors for the isotherm shape. Importantly, the model, whilst thermodynamically consistent, is macroscopic and thus computationally light and requires only a small number of physically meaningful parameters.

Phase diagram of the lattice fluid with SRLA-potential on the plane triangular lattice

The lattice system with competing interactions (repulsive between nearest neighbors and attractive between nextnext-nearest neighbors) on a triangular lattice is studied. The possibility of existence of two types of ordered phases in the system is established. The initial lattice was splitted into a system of four identical triangular sublattices to describe the ordered phases. The geometric order parameter of the system is introduced. Using the order parameter, the critical value of the interaction parameter is determined and the phase diagram of the system is constructed. The dependence of the critical parameter of the model on the ratio of intensity of competing interactions is investigated. The simulation data for the chemical potential are compared with the results of the quasichemical approximation. It is shown that the quasichemical approximation results in an adequate assessment of the equilibrium properties of the model in the range of its applicability.