Homogeneous Trimethylamine Quaternization and Properties of Polysulfone Hydroxide Exchange Membrane

Homogeneous trimethylamine quaternization of polysulfone was successfully performed by using DMAc / aqueous trimethylamine mixed solvent. Properties,such as hydroxide conductivity,ion exchange capacity( IEC),water uptake,swelling ratios and thermal stability were characterized for both homogeneous and heterogeneous trimethylamine quaternized membranes. Experimental data shows that IEC of heterogeneous and homogeneous membranes is ranging from 0. 52 to 1. 13 mmol / g and 0. 56 to 1. 28 mmol / g respectively. IEC and quaternized degree( DQ) of the homogeneous PSF-Qa OH membranes are improved,that is,the IEC increases by about 10%,and the water uptake increases by about 8. 8%. What is more,the increase of ion conductivity is much greater than that of the IEC and water uptake. For example,when IECmis 1. 0 mmol / g,the homogeneous membrane exhibits conductivity of 18 m S / cm( 20 ℃) and 34.8 m S / cm( 60 ℃),which increase by about 29. 5% and 40. 3%,respectively,as compared with that of the heterogeneous membrane( 13. 9 m S / cm( 20 ℃) and 24. 8 m S / cm( 60 ℃)). Furthermore,the onset decomposition temperature TODof two kinds of membranes reaches 159 ℃,which is much higher than typical operating temperature of fuel cell.