(647d) Nanocomposite Membranes for Fuel Cells

Proton exchange membranes (PEMs) were prepared using supramolecular polymers. Supramolecular forces may be used to induce phase separation. The resulting phase separation provides unique structures with both proton conducting and non-conducting phases. The supramolecular approach consists of membranes which have hydrophilic blocks (sulfonated) and hydrophobic blocks (nonsulfonated, aromatic) linked by hydrogen bonds. This creates two-directional proton conductivity caused by controlled phase separation accomplished using hydrophilic head groups which interact with hydrophobic blocks. Polybenzimidazole (PBI) copolymer was synthesized from isophtalic acid and 3,3'-diaminobenzidine tetrahydrochloride dehydrate which produce a hydrophobic block. Hydrophilic polyamide (PA) blocks were synthesized from isophtalic acid and 4,4'-diamino-2,2'-biphenyldisulfonic acid. The addition of pentadecylphenol (PDP) forms supramolecular structures via phase separation (hydrophilic ? hydrophobic). Composite membranes were also synthesized from polyamic acid and organoclay treated acid. The supramolecular sulfonated-PA / PDP / PBI membrane was tested in both the tangential and radial directions. Proton conductivity for this membrane is 3.3 x 10-3 S/cm in the tangential direction and 1.03 x 10-3 S/cm in the radial direction. In addition, proton conductivity for the composite membrane is 2.56.10-2 S/cm (80 oC). The focus of this presentation is on a nanocomposite membranes prepared from PBI and heteropolyacids (HPA). This membrane will provide high operating temperatures and high proton conductivity. Supramolecular polymers will be used for facilitated proton transport.