## 9 Application of Derivatives of Styrene in Membrane of Fuel Cells
### Styrene-Ethylene-Butylene-Styrene (SEBS)
When alkaline stability is tested, the SEBS-based membrane shows only 6.23% ion conductivity declining under a 2 M NaOH solution and for a time period of 1400 h. [Figure 7d]. The results show that the SEBS-based membrane shows a power density value of 247.86 mW cm\({}^{-2}\) which depicts its great potential in the application of AEMFCs [Figure 7e]. PAP polymers with an ether-free polymer back chain are attracted by scientists nowadays to make membranes for AEMs due to its high ion conductivity and alkaline stability. Despite high conductivity, the drawbacks such as low mechanical strength and weak phase separation restrict its direct usage in electronic devices. Some researchers try crosslinking different forms of PAP with SEBS to further enhance its physical and electrochemical properties. As an example, [PERSON] and his colleague scientists [127] prepared membrane with the crosslinking of PBB polymer with SEBS polymer using their different ratios for changing the crosslinked degree. The modified membrane with 40% degree of crosslinking shows a young's modulus and elongation values of 486 MPa and 70%, respectively. Moreover, due to the hydrophilic nature of SEBS, the membrane delivers an ion conductivity value in the range from 72.28 to 146.25 mS cm\({}^{-1}\) with maximum captured water contents and boosted structure. With high mechanical strength and conductivity, the membrane shows a power density value of 1042 mA cm\({}^{-2}\) with a voltage value of 1.8 V. The results also show that when tested, the alkaline stability of the membrane for 720 h. and at 2 M KOH for a temperature of 80 \({}^{\circ}\)C, it retains a conductivity value of 99%. For oxidative stability, it is also able to sustain the conductivity value up to 98% when tested for a time period of 120 h. and at a temperature of 60 \({}^{\circ}\)C.  
[PERSON] and his colleague scientists [128] synthesized the SEBS-based membrane by using Friedel-Crafts acylation and a ketone reduction reaction. A long alkyl chain was introduced onto styrene to resist the formation of cations and promote the resistance of alkaline. These are the base materials used for the membranes. SEBS-C6-Br is the brominated form of SEBS, and SEBS-C6-MDA is the membrane after modification with caged double cations. An SEBS-grafted group of cations attracts more water and increases the ion conductivity of the membrane. The graph shows the water uptake percentage of the membranes with different TPIP crosslinking percentages (0%, 10%, 15%, 20%). Water uptake is crucial for ion conductivity in AEMs, as it facilitates the transport of hydroxide ions [Figure 8a,b]. The grafted cations contain a large hindrance property which  
Figure 7: (**a**) Schematic diagram of synthesis of PTP-based membrane containing SEBS. (**b**) Temperature vs. ionic conductivity and (**c**) temperature dependence Arrhenius curve for synthesized SEBS-based PTP membranes [126] (**d**) ion conductivity retension against time (**e**) current desnity vs cell potential. protects the membrane from degradation when hydroxyl groups attach to it. On the other hand, membrane containing SEBS-crosslinked photon-induced photopolymerization (TPIP) enhances the resistance against swelling and mechanical strength [Figure 8c]. The graph in Figure 8c illustrates the swelling ratio of the membranes under different TPIP crosslinking percentages. With 15% TPIP, the SEBS membrane containing cations delivers an ionic conductivity value of 86.76 mS cm\({}^{-1}\) at a temperature of 80 \({}^{\circ}\)C. Moreover, its tensile strength value and elongation reaches 18.75 MPa and 395.9%, respectively. With these enhanced properties, the modified membrane is able to deliver a stable alkaline fuel cell performance for 2200 h. with just a 20.81% degradation rate at a temperature of 80 \({}^{\circ}\)C under 2 M NaOH solution. and alkali stability [Figure 8d]. With 15% TPIP, the modified SEBS membrane is also able to deliver a power density and current density values of 221 mW cm\({}^{-2}\) and 460 mA cm\({}^{-2}\), respectively.