Influence of ionic liquids on the properties of sulfonated polymer membranes

Modification of sulfonated poly(ether ether ketone) membranes by impregnation with the ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate for proton exchange membrane fuel cell applications

“…According to published data, the PEEK has a T g at ∼150°C and a melting temperature at 335°C; the T g of SPEEK occurrs at temperatures above 150°C (200–220°C); this depends on the degree of sulfonation . The DSC results show the T g of the PEEK at 153°C, similar to the value found in the literature.…”

“…Proton replacement with the BMI + cation causes a decrease in the hydrophilic domains, which are generated from the sulfonic acid groups. As shown in a previous work of our group , that the water uptake of the SPEEK membranes increased significantly with increasing temperature, up to 90°C; however, at this temperature, swelling became predominant and the membrane dissolved. The SPEEK membranes modified with the BMI + cation, have similar water uptake at room temperature, but easily dissolve at temperatures as low as 70°C.…”

“…The incorporation of BMI + cations from the 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMI.BF 4 ) ionic liquid into SPEEK membranes is dependent on the time that the membrane was immersed in the IL solution, as shown in a previous study . It consists of the replacement of H + cations originally present in SO 3 H groups by l‐butyl‐3‐metylimidazolium cations from the IL.…”

“…After this, the mixture was poured onto glass plate molds. The solvent was evaporated under exhaust at room temperature for 1 week and then the membranes were transferred to an oven at 80°C for 72 h. The membranes were modified by immersion in a solution of 5 mmol BMI.BF 4 in 50 mL of ultrapure water (2 mS cm −1 ), i.e., at a concentration of 0.1 M at room temperature, as previously described , for different contact times. After immersion, the membranes were washed with deionized water to remove any residual IL and avoid its physical adsorption on the membrane surface .…”

A Study of Mechanical Properties of Polymer Composite Membranes with Various Ionic Liquids at Elevated Temperatures

“…Thereby ILs are good candidates for substituting water as an essential component for proton conducting in HT PEMFCs in anhydrous conditions. Several key properties have been successfully improved by incorporating ILs in SPEEK membranes, including thermal stability and proton conductivity [11,15]. IL/SPEEK composites are also paving the way to a new types of composite membranes by including additional components in addition to ILs, and opening wide variety of possibilities for further enhancement of PEM properties [13].…”