- 2:42 PM
553h

Molecular Dynamics Study on Hydrated Water-Soluble Dendrimer-Grafted Polymer Membrane for Pemfc

Seung Soon Jang, Chemsitry, California Institute of Technology, Materials and Process Simulation Center, Beckman Institute MC 139-74, Pasadena, CA 91125 and William A. Goddard III, Chemistry and Chemical Engineering Division, California Institute of Technology, Materials and Process Simulation Center, Beckman Institute MC 139-74, Pasadena, CA 91125.

We have investigated a molecular architecture in which water-soluble dendrimers are grafted onto a linear polymer for application to polymer electrolyte membrane fuel cells. Using full-atomistic MD simulations, we examined the nanophase-segregation and transport in hydrated membrane consisting of such a new architecture. In order to determine the effect of the linear polymer backbone on the membrane properties, we simulated three different types of linear polymers: poly (epichlorohydrin) (PECH), poly (styrene) (PS) and poly (tetrafluoroethylene) (PTFE) in combination with the second-generation sulfonic poly aryl ethereal dendrimer, which results in PECH-D2, PS-D2, and PTFE-D2. From our simulations, we found that the extent of nanophase-segregation in the membrane increases in order of PECH-D2 < PS-D2 < PTFE-D2 at the same water content, which is determined by the interaction between backbone polymer and water. By analyzing properties such as structures in water phase, water dynamics and proton transport, we found that these properties are strongly coupled with the extent of nanophase-segregation as well as the water content in the membrane. As the nanophase-segregation proceeds, the structure in water phase, water dynamics and proton transport becomes similar to those in bulk water. Based on the observations from our simulations, we expect that the PTFE-D2 may have a comparable performance with Nafion and Dendrion.