Preparation And Properties Of Side Chain Sulfonated Poly(aryl Ether Ketone Sulfone)and The Composite Proton Exchange Membranes

Proton exchange membrane fuel cells（PEMFCs）are the energy conversion devices that can convert chemical energy into electrical energy directly.As a kind of PEMFCs,direct methanol fuel cells（DMFCs）are fueled by methanol and they have been extensively studied by scientists due to their non-polluting,efficient,fast load response and high energy density.As the key component of DMFCs,proton exchange membranes（PEMs）determine the life and performance of DMFCs.Nowadays,perfluorosulfonic acid PEMs such as Nafion?produced by DuPont and Flemion?developed by Asahi Glass have been mostly commercialized.However,high fuel penetration and processing difficult hindered their development.For this,the research about materials could replace them is necessary.Sulfonated aromatic polymer especially sulfonated poly（aryl ether ketone sulfone）has been the most promising alternative materials due to excellent mechanical properties,thermal properties,chemical stability and low cost.They could conduct protons by introducing-SO₃H.For higher proton conductivity,the higher-SO₃H ratio in the materials is the usually choose.However,the high-SO₃H ratio resulted excessive water uptake and dimension changes which weakened the mechanical properties.In this work,we synthesized sulfonated poly（aryl ether ketone sulfone）with-NH₂ on main chains（Am-SPAEKS）by condensation firstly.Then grafted alkyl side chains terminated with-SO₃H to Am-SPAEKS X and obtained a series of comb-shaped sulfonated poly（aryl ether ketone sulfone）membranes SPAEKS-PSA X.The comb-shaped structures improved the proton transport ability of membranes.The membrane SPAEKS-PSA 15 exhibited the highest proton conductivity of 0.097 S cm^-1 under 80°C and 100%relative humidity conditions.Meanwhile,that of membrane no comb-shaped structure was only 0.069 S cm^-1.The methanol permeability of comp-shaped membranes ranged from 7.56 cm² s^-1 to 9.44 cm² s^-1,which is quite lower compared to Nafion?117(22.37cm² s^-1).Although the comb-shaped structure decreased the thermal properties,oxidation stabilities,and mechanical properties of SPAEKS-PSA X membranes to some extent,it is still in an acceptable level for DMFCs applications.For improving the proton conductivity further,we prepared a series of composite membranes SPAEKS-PSA/PWA 30/TEOS X by introducing phosphotungstic acid（PWA）and ethylsilicate（TEOS）into SPAEKS-PSA X matrix.PWA enhanced the conductivity of composite obviously and the membrane SPAEKS-PSA/PWA 30/TEOS 4 exhibited high proton conductivity of 0.128 S cm^-1 which is much higher than that of SPAEKS-PSA 15membrane.Meanwhile PWA and TEOS could prevent the water leakage effectively,after being placed in 80^oC conditions 30 mins,the weight loss of membrane with 4%TEOS is only 2.94%.As scanning electron microscope image displayed,the PWA particles were dispersed more uniform after introducing TEOS.Considered all the parameter of composite membranes especially the proton conductivity and water retention,the SPAEKS-PSA/PWA 30/TEOS 4 membrane was most promising for DMFC applications.