## 9 Application of Derivatives of Styrene in Membrane of Fuel Cells
### Polystyrene
The membrane exhibits high thermal and oxidative stability but lower water uptake and proton conductivity as the amount of polystyrene-based synthesized polymer increases. Under hydrated conditions, the polymer blend membrane with 1:1:4 synthesized polymer and PVC contents shows a proton conductivity value of 7.8 \(\times\) 10\({}^{-5}\) S cm\({}^{-1}\). [PERSON] and his colleague scientists [119] synthesized a fibrous mat as an anion exchange membrane which consists of styrene\(-\)co\(-\)vinylbenzyl chloride\(-\)co\(-\)acrylonitrile copolymer by electrospinning technique using organic reaction blend. The unique phase modification of the membrane is responsible for its high ion conductivity. Moreover, the hydrophilic groups in the modified nanofiber mat result in a high water uptake, low swelling, and high IEC as the chemical composition of the organic blend in the membrane changes. With the ration of 3:5:2 of styrene-vinylbenzyl chloride-acrylonitrile, the modified membrane shows an ion conductivity value of 214 mS cm\({}^{-1}\) at a temperature of 80 \({}^{\circ}\)C. With its superior properties, the modified anion exchange membrane retains up to 94% of its ion conductivity after soaking in 1 M potassium hydroxide (KOH) solution for 72 h. A summary of these studies is provided in Table 2.  
In conclusion, polystyrene, a synthetic polymer derived from styrene monomers, is widely used in various applications, including fuel cells, due to its lightweight, rigid, and moldable nature. However, its brittleness and hydrophobic characteristics limit its direct use. To overcome these limitations, polystyrene is often modified or combined with other materials to enhance its properties. For instance, [PERSON] et al. [110] synthesized a polystyrene-based composite membrane with dual-functional graphene oxide, which improved proton conductivity and reduced methanol crossover in direct methanol fuel cells (DMFCs). Similarly, [PERSON] et al. [111], developed a composite membrane using sulfonated poly(styrene-co-maleic anhydride), poly(ethylene glycol), and silica, which exhibited high mechanical strength and low methanol permeability, making it suitable for DMFCs. Polystyrene can also be sulfonated to enhance its hydrophilic properties, as demonstrated by [PERSON] et al. [113], who grafted polystyrene sulfonic acid onto graphene oxide and combined it with SPEEK to create a composite membrane with high proton conductivity and low methanol crossover. This membrane outperformed both pristine SPEEK and commercial Nafion 117 membranes in terms of power density. These advancements highlight the potential of polystyrene-based membranes in fuel cell applications, offering improved performance, durability, and cost effectiveness compared to traditional materials like Nafion. By leveraging modifications such as sulfonation, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Types of Materials** & **Types of Fuel Cell** & \begin{tabular}{c} **Ion** \\ **Conductivity** \\ **(mS cm\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Current** \\ **Density** \\ **(mA cm\({}^{-2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Power Density** \\ **(mW cm\({}^{-2}\))** \\ \end{tabular} & **Ref.** \\ \hline styrene\(-\)co\(-\)vinylbenzyl chloride\(-\)co\(-\)acrylonitrile copolymer & AEMFC & 214 & - & - & [119] \\ \hline poly(styrene sulfonic acid-co-1-vinylimidazole-co-styrene) & PEMFC & 7.8 \(\times\) 10\({}^{-2}\) & - & - & [118] \\ \hline NaSS-4 VP & PEMFC & 71 & - & - & [117] \\ \hline SSA/cellulose acetate & DMFC & 4.77 & - & 24.6 & [114] \\ \hline Polystyrene/graphene oxide & DMFC & 73 & & 170 & [113] \\ \hline Polystyrene/PE/graphene oxide & DMFC & - & - & 78 & [110] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Polystyrene-based membranes for application in fuel cells. copolymerization, and nanocomposite formation, polystyrene-based membranes can address key challenges in fuel cell technology, contributing to the development of sustainable energy solutions.