SAXS Characterization of Ordered Ion-Containing PolymersRobert B. Moore, Virginia Polytechnic Institute and State University, DMR 0923107

Perfluorosulfonate ionomers (PFSIs) have been shown to be of great importance for polymer electrolyte membrane fuel cell (PEMFC) applications. Understanding how PFSI’s structure and morphology relate to the transport of mobile species presents a challenge for designing next-generation fuel cell materials. The understanding of how processing can influence the ionic and crystalline domains will allow for tailored ordering of the structures that will enhance transport properties and fuel cell efficiency.

-Small Angle X-ray Scattering (SAXS) and Multi-Axis Pulsed-Field-Gradient NMR results show ionic domain orientation and improved conductivity in stretch direction.

-Synchrotron SAXS was used to study time-resolved morphological development during solution processing of nanostructured membranes

Figure 2. Orientation of hydrophilic channels with uniaxial stretching. With increasing draw ratio, the hydrophilic channels orient along the draw direction.

Figure 1. Synchrotron SAXS data of a uniaxially stretched PFSI.

Figure 3. A: SAXS of Nafion in solution,B:Morphologyical development during solution processing using In-situ SAXS . C: SAXS of Nafion in solid state.

A

C

B

Development of crystalline region

Disappearance of solution structure

Development of ionic aggregates

The small-angle X-ray scattering (SAXS) system that was purchased under the DMR-Award # 0923107 has been used to enhance the technical impact of many research groups at Virginia Tech, and others across the US. These interdisciplinary collaborations have involved many under-represented groups. Recent results from this instrumentation were presented by at least 10 students at the IUPAC World Polymer Congress and other ACS meetings.

During the past year, a graduate course on polymer characterization was taught at Virginia Tech. The SAXS instrumentation was utilized by this class in an experiment for determining crystalline order within oriented polymers.

a) Students learning to use SAXS for their research

b) Probing the morphological development of solution processed Nafion using real-time SAXS at Argonne National Lab

SAXS Characterization of Ordered Ion-Containing PolymersRobert B. Moore, Virginia Polytechnic Institute and State University, DMR 0923107