Preparation And Properties Of Poly(N-aryleneindole Ether)s As Proton Exchange Membrane

Proton exchange membrane fuel cell is a kind of energy conversion device which can transform chemical energy into electricity. Despite considerable effort, the availability of commercial Nafion membrane is limited to a certain extent for a variety of reasons, including expensive and high methanol permeability, etc. Accordingly, the development of a new strategy for construction of new proton exchange membrane material especially sulfonated aromatic polymers still remains an attractive and promising goal.However, the aromatic proton exchange membrane lately has faced a big problem that is the balance of swelling ratio, fuel penetration and proton conductivity. Usually,improving the proton conductivity requires the polymer with a high sulfonation degree,which will inevitably lead to a huge water uptake and swelling ratio. On the contrary,the result is a negative effect for dimensional stability, cell assembly and mechanical property of PEM. Therefore, how to prepare new proton exchange membrane materials with high proton conductivity, excellent size stability, and low fuel penetration is still the core of research in fields of fuel cell.In order to obtain new proton exchange membrane materials with a combination of high proton conductivity and excellent swelling resistance performance, in this study,we intend to introduce the indole groups into the polymer chain to assist proton transmission through the establishment and elimination of the cation-? interaction between indole and H+, the process of which is similar to the proton transmission between sulfonic acid groups. In addition, we hope that the cation-? interaction can enhance the interaction of the molecular chain in proton exchange membranes, so as to further improve their swelling resistance ability. Based on the reasons, we prepared a series of different degree of sulfonated Poly(N-aryleneindole ether)s(SPEIN-x) in a way of C-N/C-O coupling copolycondensation reaction. Through the methods such asFTIR and 1HNMR spectra, we characterized the polymer structures. The results were in good agreement with the target products. After casting and acidification, we obtained the acid form proton exchange membrane materials. These SPEIN-x proton exchange membranes exhibited excellent proton conductivities, as SPEIN-50 could reach 0.1286S/cm in 80 o C, which is higher than Nafion 117. Moreover, SPEIN-x showed excellent swelling resistance under the condition of high temperature at 100 o C. With a swelling ratio lower than 42%, it endowed the proton exchange membrane a good dimension stability under high temperature, which also provided SPEIN-x a low methanol permeability, only 1/35 to 1/12 of 117 Nafion membrane. Furthermore, the film displayed outstanding mechanical properties with a tensile strength higher than 53 MPa,which could satisfy the application requirements of proton exchange membrane.It is well known that the phase separation can further improve the proton conductivity and solvent resistance of proton exchange membrane. Thus, in order to obtain new sulfonated Poly(N-aryleneindole ether)s with excellent comprehensive performance, in this thesis, we also successfully synthesized a series of mutiblock proton exchange membranes, the hydrophilic segments of which contained indole groups. The test results indicated that the mutiblock proton exchange membranes had higher proton conductivity, better dimensional stability than the random sulfonated Poly(N-aryleneindole ether)s. The proton conductivity of X20Y20 at 80 o C could reach0.1406 S/cm, which is 1.4 times of Nafion 117. In addition, with the excellent mechanical strength and high resistance to methanol permeability, the swelling ratio of the mutiblock proton exchange membrane was lower than 22%. In a word, the introduction of the indole groups provided the target proton exchange membrane with an excellent proton conductivity and swelling resistance. We believed that the type of sulfonated poly(N-aryleneindole ether)s proton exchange membrane materials could be a good choice for fuel cells in future.