Preparation And Characterization Of Proton Exchange Membranes Based On 2-acrylamido-2-methylpropane Sulfonic Acid

Proton exchange membrane(PEM) is one of the most important components in proton exchange membrane fuel cell(PEMFC). Nafion(DuPont), which is the mostly used membrane in fuel cells at present, is a type of proton exchange membrane with excellent performance. But it has disadvantages of high methanol permeation and high cost. So it is important to develop noval types of proton exchange membranes with high proton conductivity and low methanol permeation.Poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) is a typical anion polyelectrolyte with sulfonic group. It is often be used to produce proton exchange membrane duo to its high ion conductivity. But PEMs based on PAMPS have disadvantages of easy swellen and pore mechanical property, so they must be copolymerized with oil monomer to change their mechanical property. But, AMPS is a water-soluble monomer and it is indissoluble in most oil monomer.In this paper, AMPS was neutralized with 1-methyl imidazolium and ionic liquid was formed. Then the ionic liquid was then in-situ polymerized with styrene/acrylonitrile. After treating with acid, a piece of homogeneous proton exchange membrane containing AMPS was produced. Properties like water uptake behavior, ionic exchange capacity(IEC), methanol permeation, proton conductivity, thermal stability and oxidative stability of the membranes were characterized. The results showed that, the proton exchange membrane showed good thermal stability and high proton conductivity as high as 3.8×10-2 S/cm at room temerature. The methanol permeation of the membrane was 6.8×10-7 cm2 s-1. The proton conductivity of the membrane reaches the same level of Nafion117(6.0×10-2 S/cm), while the methanol permeation was an order of magnitude lower than that of Nafion117(1.68×10-6 cm2 s-1). Properties of the PEMs, such as proton conductivity, methanol permeation, can be controlled by changing the content of PAMPS and cross-linking agent.In order to obtain PEMs with low methanol permeation, we prepared organic/inorganic composite PEMs based on PAMPS. After blending with acrylic acid(AAc) and SiO2 nanoparticles which were modified with ionic liquid on the surface(SiO2-IL), we obtained PEMs with high proton conductivity(3.9×10-3 S/cm) and low methanol permeation(9.7×10-8 cm2 s-1). And the properties of the PEMs, such as water uptake behavior, proton conductivity and methanol permeation were characterized. It was showed that, this type of PEMs have high proton conductivity(10-3 S/cm order of magnitude) at high temperature.