Synthesis And Characterization Of Multiblock Sulfonated Poly(Arylene Ether Sulfone) For Proton Exchange Membranes

A series of novel multiblock SPAES were successfully developed. Blend membranes from bSPAES and SPI were prepared. Their properties such as ion exchange capacity (IEC), water uptake (WU), dimensional change, proton conductivity (a) as well as water stability were investigated in details.Hydrophilic/hydrophobic multiblock SPAES copolymers (SN-bSPAESs) were synthesized via step-growth polymerization in the presence of potassium carbonate. The structures of oligomers and multiblock copolymers were confirmed by1H NMR spectra. All bSPAES membranes showed good water stability. For example, M(6/4)-b(12/8) (IEC=2.42 meq/g) still remained good mechanical property after aging test in water at 100℃for 24h. All bSPAESs showed higher proton conductivities than that of Nafion 112 in water. The proton conductivity of M(4/6)-b(8/12) in water at 60℃was 0.208S/cm, which was about 1.5 times to that of Nafion (0.142S/cm). At the similar IEC value, their proton conductivity and water uptake were significantly affected by the block length, which a and WU increased with the increase block length.A series of high sulfonated degree/low sulfonated degree multiblock copolymer (SS-bSPAESs) were successfully synthesized. SEM micrographs revealed that there was no obvious phase separation occurred in the membrane. All of the SS-bSPAESs membranes showed good water stability that they could still remain good mechanical property after aging test in water at 100℃for 200 h with the IEC value of 2.08 meq/g. The proton conductivities of these membranes were all higher than that of Nafion 112 when the relative humidity (RH) was over 60%.A series of sulfonated SN-bSPAES/SPI blend membranes were prepared by solution casting method. Blend membranes were transparent and displayed smooth surfaces. SEM microgrphs also showd that there was no obvious phase separation occurred, indicating the good compatibility of the two materials. Due to the introduction of SPI, dimensional stability and hydrolytic stability of blend membrane were highly enhanced in comparison to the SN-bSPAESs.