(437d) Computational Study of Water and Toxins Permeability in Sulfonated Sibs Copolymers

Andzelm, J., U. S. Army Research Laboratory
Sloan, J., US Army Research Laboratory
Napadensky, E., US Army Research Laboratory
Crawford, D., US Army Research Laboratory
Rigby, D., Accelrys Inc

Sulfonated polystyrene-b-polyisobutylene-b-polystyrene copolymer (sSIBS) forms a microphase separated membrane where one phase is impermeable, lightweight and flexible while the other ionic phase is rigid, strong and has high water transport performance. For these reasons, sSIBS can be considered as a promising material for applications to textiles where breathable yet protective clothing are required.

In this work, we have used multiscale modeling to gain understanding of static and dynamic properties of this polymer at detailed atomistic and mesoscale level. These results were then utilized to calculate the permeabilities of both water and chemical toxins using finite element methods.

In our earlier work, we studied water permeability in sSIBS membrane at low sulfonation levels (Molecular Simulations 32, 163 (2006)). However, the present work focuses on a much higher sulfonation levels where the diffusion and solubility of water increases significantly. The diffusion coefficients were calculated and compared with the recent experimental data. It was found that the presence of metal ions lowers the diffusion coefficients. The mechanism of diffusion and effect of membrane architecture will be discussed. Our results suggest a hopping mechanism occurs for water diffusion due to the hindered movement in narrow channels of polymer and also strong interaction with the ionized sulfonic acid groups. Simulations were performed for using both dispersed and ?blocky? architecture of copolymer. We will compare the diffusion characteristics of water and two known chemical toxins (mustard gas and dimethyl methyl phosphonate (DMMP)) in both materials.