NAMS 2002 Workshop - ICOM 2008

Membrane Modeling II - Gas Separation – 1 – Keynote
Tuesday July 15, 2:15 PM-3:00 PM, O’ahu/Waialua
Modeling Approaches for the Design of High Performance Polymer Glassy
Membranes for Small Gas Molecule Separations
P. Pullumbi (Speaker), Air Liquide, Jouy-en-Josas, France - pluton.pullumbi@airliquide.com
E. Tocci, Institute for Membrane Technology ITM-CNR, Rende (CS), Italy
M. Heuchel, GKSS, Teltow, Germany
S. Pelzer, GKSS, Teltow, Germay
The need to shorten the research cycle of novel materials used in gas
separations technologies by coupling several computational approaches with
experimental techniques has been the driving force for the recent developments
in molecular modeling technology. Modeling of gas transport through polymer
membranes is not straightforward because of the complexity of phenomena
involved. In this study we propose a methodology composed out of several
computational methods combining atomistic modelling of models of polymer
membrane materials with Molecular Dynamics (MD) calculations as well as
transition state theory (TST) simulation of transport properties of small gas
molecules in these models followed by Quantitative Structure Activity
Relationship (QSAR) analysis for the design of new polymer materials. The
quality of the predicted transport properties of small gas molecules through
membrane models strongly depends on the quality of these last ones. The large
scatter often observed in simulated values of small gas molecule diffusion
coefficient and solubility in the same glassy polymer membrane is related to the
methodology applied for generating reproducible packing models of the
membrane. In order to reduce this scatter, numerical analysis of structural
features of the membrane model has been used for pre-selecting only the
realistic ones for further use in simulations by means of transition state theory
(TST) approach. In this study more than 200 polymer membrane packing models
corresponding to more than 60 different polymers have been prepared.
Simulated values via TST of Solubility and Diffusion coefficients for small gas
molecules have been predicted for each packing model. Detailed Free Volume
analysis has been carried out for each cell of the data set. A multi- level QSAR
approach has been adopted in order to determine, first, the relevant descriptors
(including information of free volume distribution and dynamics) and second,
determine of the specific weight of each descriptor. Several “separated” QSAR
studies (QSAR-monomers, QSAR-chain, QSAR- Cell) have been carried out and
several descriptors have been selected for the composed study. The proposed
computational methodology in this study whose validation is under progress,
contributes to the joint experimental-theoretical efforts towards the rational
design of membranes with improved properties.
The authors acknowledge the European Community for its partial support (Project: NMP3-CT-
2005- 013644 MULTIMATDESIGN ).