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Towards Design of Functional Polymer Membranes Using ERmod

Isamu Shigemoto

Research Associate
Advanced Materials Research Laboratories, Toray Industries Inc.

Toray is implementing Green Innovation Business as a group-wide project in order to bring leading edge technologies to bear on global environmental problems. This project is widely expected to achieve polymer membranes as advanced materials essential for ameliorating and solving global environmental problems, whether as polyelectrolyte membranes for the fuel cells that are expected to be the next generation energy source, or reverse osmosis membranes for seawater desalination considered as a means for ensuring water resources in arid areas. To this end, our Computational Chemistry Group is working to develop and apply techniques for
the analysis of permeability using molecular modeling, with the target of designing polymer membranes with advanced selective permeability. 
There are two factors that determine the permeability of a substance, diffusivity and solubility. The approach which we considered initially for the former was to find the diffusion coefficient using molecular dynamics simulations, and for the latter, to calculate the free energy of solvation. However, free energy is a physical quantity with one of the highest calculation loads in molecular modeling, and there was no way to calculate the solvation free energy of a small molecule in polymer within a
reasonable simulation time and work load involved. 
In 2007, I and Professor Matubayasi were both invited by chance to a lecture on the subject. The lecture about methods of energy representation was the opportunity for asking Professor Matubayasi to undertake joint research with us. The original program was not envisaged as applying to giant molecules like polymers, and so under Professor Matubayasi’s guidance, we undertook research into methods of calculating the interaction energy of polymers and small molecules, improving
energy functionals and so on. As a result, we succeeded in building techniques for calculating free energy of solvation with realistic calculation times and accuracy. At the end of last year, we published an article authored jointly with Professor Matubayasi in J.Chem.Phys. Now, it is beginning to bear fruit in the form of polymer electrolytes and separation membranes using this technology, and it is also highly regarded within the company too. 
In this way we arrived at ERmod by a stroke of luck, but when the company researchers want to try leading edge simulations that are impossible with general-purpose software, it is not easy to find software that matches the company’s needs. For this reason, I think that the gradual establishment of MateriApps will be beneficial for future academic-industrial matching. In particular, if there are extensive tutorials and article summaries, it will be easy to see how they can be used for actual research, which will be very helpful.