title: Molecular Simulation Study of Gas Solubility and Diffusion in a Polymer-Boron Nitride Nanotube Composite.
abstract: We study the possibility of using polymer composites made of a polymer and boron nitride nanotubes (BNNTs) as a new type of membranes for gas separation. The polymer used is amorphous poly(ether imide) (PEI), and zigzag BNNTs are used to generate the composites with the PEI. The solubilities and self-diffusivities of CO2 and CH4 in the PEI and its composites with the BNNTs are calculated by molecular dynamics (MD) simulations. The molecular models of the PEI and its composites with the BNNTs are generated using energy minimization and MD simulation, and the Universal Force Field is used to represent the interactions between all the atoms. The morhology of the composites are characterized and are compared with that of PEI. The accuracy of the computations is tested by calculating the gases' solubilities and self-diffsivities in the pure PEI and comparing them with the experimental data. Good agreement is obtained with the data. The computed diffusivities and solubilities in the polymer-BNNTs composites are much larger than those in the pure polymer, which are attributed to the changes that the BNNTs induce in the polymer composite's free-volume distribution. As the mechanical properties of the polymer-BNNTs composites are superior over those of the pure PEI, their use as a membrane for gas separation offers distinct advantages over the pure polymer. We also demonstrate that, calculating the diffusion coefficients with MD simulations in the NPT ensemble, as opposed to the common practice of utilizing the NVT ensemble, leads to much more accurate results.
authors: Mork Family Department of Chemical Engineering & Materials Science, University of Southern California , Los Angeles, California 90089-1211, United States.
authors: Congyue
authors: C
authors: Wang
authors: Mork Family Department of Chemical Engineering & Materials Science, University of Southern California , Los Angeles, California 90089-1211, United States.
authors: Preeti
authors: P
authors: Jagirdar
authors: Mork Family Department of Chemical Engineering & Materials Science, University of Southern California , Los Angeles, California 90089-1211, United States.|Materials and Process Simulation Center, California Institute of Technology , Pasadena, California 91125, United States.
authors: Saber
authors: S
authors: Naserifar
authors: Mork Family Department of Chemical Engineering & Materials Science, University of Southern California , Los Angeles, California 90089-1211, United States.
authors: Muhammad
authors: M
authors: Sahimi