Novel Proton Exchange Membranes Based On Sulfonated Poly(Phthalazinone Ether Sulfone Ketone)

Proton exchange membrane (PEM), the key part of proton exchange membrane fuel cell (PEMFC), not only separates the fuel from oxidant to avoid direct contact, but also transfers proton form anode to cathode. The properties of PEM considerably impact on the PEMFC performances such as output power, energy efficiency and service life.In order to overcome low thermal stability, high fuel permeability and high cost of perfluonated sulfonic membrane (such as Nafion), in this dissertation, sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) were prepared by sulfuric acid or fuming sulfuric acid sulfonating agent based on poly(phthalazinone ether sulfone ketone) (PPESK) using homogeneous sulfonation method. After optimization (organic solvent) of dissolution-precipitation separation method, effective removal of residual sulfonating agent and high yield (over 96%) were achieved. For further investigation of the separation process, a mathematical model describing yield was established, and the appropriate preferences were obtained by regression of the experimental data.The SPPESK membranes were prepared by solution casting method, and the effect of the casting solvent and curing temperature on the morphology were investigated. Flat and uniform SPPESK membranes were obtained under 40-60℃curing temperature and N-methylpyrrolidone (NMP) as the casting solvent. SPPESK membrane had high thermal stability (T_d > 300℃), appropriate water uptake and swelling rate, and shows excellent methanol resistance (permeability of SPPESK membrane was 1/32-1/42 of that of Nafionl 15). Though having higher apparent energy, conductivity of SPPESK membrane was still fairly lower than that of Nafionl 15. The primary H₂/O₂ and CH₃OH/O₂ single cell discharge experiments were successfully carried out and the maximum output power were 426.0 and 9.63 mW/cm², respectively.In order to improve electro-property, the covalent crosslinked SPPESK with glycol, glycerol or poly(vinyl alcohol) (PVA) membranes were prepared. Compared with small molecular glycol and glycerol, polymer PVA was much advantageous to be crosslinker due to lower crosslinking temperature and higher stability of crosslinked membranes. Because the crosslinking network not only increased the molecular weight but also restricted the polymer chain movement, Crosslinked SPPESK with PVA membrane had appropriate water uptake and good dimension stability. Due to having higher ion exchange capacity (IEC) and higher acidity of SPPESK DS: 140%, the crosslinked SPPESK with PVA membrane had considerably enhanced electro-property, in which conductivity almost reached twice of that of SPPESK 81%.In order to overcome the brittleness of crosslinked covalent PEM, the polymer blending blend membranes of SPPESK and poly(vinylidene fluoride) (PVdF) were prepared, taking the advantages of the hydrophobic and quite compatible nature of PVdF. In these blending membranes, a hydrophobic network composed by PVdF and SPPESK main chain was formed, which not only restrained excessive swelling and but also avoided too much brittleness. Furthermore the blending PVdF/SPPESK blend membrane had higher conductivity that similar to Nafion115.