## 9 Application of Derivatives of Styrene in Membrane of Fuel Cells
### Styrene-Ethylene-Butylene-Styrene (SEBS)
The results show that the membranes are able to be applied in the field of fuel cells [Figure 8e]. The crosslinking method is generally required to attach one polymer with another polymer for enhancing physical and electrochemical properties of AEMs. However, in some cases, the application of crosslinking agent greatly changed the properties of membrane  
Figure 8: (**a**) Schematic diagram of synthesis of SEBS membrane based on TPIP from 0 to 20%. Graphs of temperature vs. (**b**) water uptake (%) (**c**) swelling ratio (%); (**d**) graphs of time vs. ion conductivity retention of different SEBS membranes; (**e**) graphs of current density vs. voltage vs. power density values [128]. which it unsuitable for application in fuel cells. The research approach by the scientist nowadays is to apply the crosslinking method without a crosslinking agent which minimizes the damage of polymer physical structure and maximizes the properties such as mechanical strength, reduced swelling, and ion conductivity. As an example, [PERSON] and his colleague scientists [129] synthesized the membrane composed of PPO polymer and SEBS polymer by crosslinking method without crosslinker. By using this approach, the resultant membrane has a thinness in nature and a thickness of 10 \(\upmu\)m can be achieved. Moreover, the modified membrane is able to provide a high tensile strength and elongation of 34.3 MPa and 91.6%, respectively. The hydrophilic nature of the SEBS develops ionic channels and promotes absorption of water contents to help maximize the ionic clusters. Ultimately, the hydroxide ion conductivity value of the modified membrane is high under a relative humidity value of 95% and allows the membrane in fuel cells to achieve high efficiency. When the MEA is assembled with a modified membrane, the fuel cell is able to deliver a stable performance for a time period of 300 h at a temperature of 60 \({}^{\circ}\)C. The fuel cell with modified membrane is also able to deliver a power density value of 405 mW cm\({}^{-2}\). These results are superior to the commercially available membrane which proves that the modified membranes are compatible and applicable for AEMFCs. SEBS (styrene-ethylene-butylene-styrene) has been extensively explored for fuel cell applications due to its flexibility, chemical inertness, and ability to be modified for enhanced performance. In proton exchange membrane fuel cells (PEMFCs), SEBS is often sulfonated to improve hydrophilicity and proton conductivity, making it effective for applications like direct methanol fuel cells (DMFCs) where reduced methanol crossover is critical. For anion exchange membrane fuel cells (AEMFCs), SEBS is functionalized with ion-conducting groups or copolymerized with other polymers to achieve high hydroxide conductivity and excellent phase separation. Crosslinking SEBS with materials like polystyrene, fluorine-containing polymers, or nanoparticles further enhances its mechanical strength, thermal stability, and ion conductivity. These modifications enable SEBS-based membranes to deliver stable performance, resist swelling, and operate efficiently under high temperatures and low humidity. Overall, SEBS is a versatile material that, through various chemical and structural modifications, has proven to be a promising candidate for both PEMFCs and AEMFCs, offering a balance of durability, conductivity, and cost effectiveness.