Center for Functional Nanomaterials Seminar
"Ordering Phases in Polymer Electrolyte Membrane"
Presented by Sergey Yakovlev, Lawrence Berkeley National Laboratory
Wednesday, May 29, 2013, 11 am
Bldg. 735 - Conf Rm B
Hosted by: Eric Stach
Development of sustainable energy technologies requires new materials with properties tailored for specific needs. Nano-phase-separation observed in many material systems opens a wide range of possibilities for manipulating specific properties as well as for creating new properties not observed in homogeneous systems. Generally, targeted material design requires an understanding of underlying structure. One important example of nanophase-separated system is a polymer electrolyte membrane (PEM). In PEM a hydrophilic phase provides charge transport while a hydrophobic phase is responsible for mechanical properties and stability of the material. The geometry of phase separation governs performance of membrane providing continuous pathways for charge transfer. The goal of my research is to determine the structure of conductive pathways and to design a membrane with maximum connectivity in the hydrophilic phase. This goal can be achieved by exploiting self-organization in block copolymers that produces naturally aligned nano-sized phases. This approach has already allowed us to overcome difficulties in electron microscopy imaging of ionomer morphology and to report the first direct observation of sulfur clusters in PEM. Using a block copolymer system, we have shown that the clustering reduces conductivity of the ionomer and suggested a way to reduce clustering by decreasing the size of conductive domains. The next step towards development of an improved membrane material is determining water distribution in PEM which may be achieved by advanced electron microscopy techniques.