The Modification Of Based-on Sulfonated Poly(Arylene Ether Sulfone) For Proton Exchange Membranes

Fuel cell is an electricity generated device which can turn the chemical energy in fuel into electric energy, proton exchange membrane is the key part of fuel cell. Nowadays, the most widely studied sulfonated aromatic polymer membrane become one of the most promising materials for proton exchange membrane due to its excellent thermal stability and oxidation stability, excellent mechanical properties, high water uptake and high proton conductivity. But these membrane materials had a low proton conductivity and stability at high temperatures and low humidity, it is still hard to satisfied with the actual fuel cell applications. So it is very necessary to do a further research in order to get a higher proton conductivity and stability of SPAES proton exchange membrane over a wide temperature and humidity range. This article used the method of crosslinking and nano-composited to modify SPAES membrane aimed for high performance proton exchange membrane.A series of sulfonated poly(arylene ether sulfone)(SPAES) copolymers were successfully synthesized from4,4’-difluorodiphenyl sulfone,4,4’-bisphenol and3,3’-disulfonate-4,4’-difluorodiphenyl sulfone via nucleophilic substitution polymerization. Polyacrylamide (PAM) were prepared from acrylamide and N,N-methylene-bis-acrylamide using azobisisobutyronitrile as initiator through radical polymerization, and used as starting material to prepare semi-IPN membrane during solution casting procedure simultaneously. A series of semi-IPN/SPAES-CPAM membranes was prepared by varying the molar ratio of copolymer and acrylamide, amount of crosslinking agent and the IEC of polymer matrix. The results shows that the water uptake and proton conductivity decreased with the increasing amount of acrylamide, while the dimensional stability and mechanical properties improved; as the CD(Crosslinked Degree) increased, the water uptake of semi-IPN-SPAES/CPAM membrane indicated a trendency of firstly increased and then decreased. SPAES(4/6)/CPAM10%-0.4membrane had an IEC of1.03mmol/g, whereas the water uptake and proton conductivity reached51%and191mS/cm, The constructure of semi-IPN improved the proton conductivity of membrane at low humidity. SPAES(4/6)/CPAM10%-0.4membrane had a proton conductivity of56mS/cm at80℃60%relative humidity which is similar with Nafionl12membrane.Based on the SPAES as matrix, using5wt%nanoparticles such as nanoSiO2, nanoTiO2, TiO2nanotubes and attapulgite as mixing agent, then after ball milling process, a series of SPAES composite membrane were prepared. The results indicated that adding organic nanoparticles into SPAES decreased the water uptake of composite membrane and improved the mechanical properties, the proton conductivity of composite membrane kept the same level with pure membrane. Considering of all performance, the composite membrane added TiO2nanotubes showed the best performance, the water uptake reached63%, proton conductivity reached185mS/cm, higher than pure membrane(184mS/cm) at60℃, Young’s modulus reached1.1Gpa.