Fuel cells are a promising technology to produce and develop sustainable and clean energy. One of the main component of fuel cell is polymer electrolyte membranes (PEMs). PEMs are responsible for ion conduction and act as barriers for gases and electrons during a fuel cell operation. Hence, it plays a crucial role in enhancing the efficiency and durability of fuel cells. However, the properties of PEMs are affected by its spatial arrangement and one cost- effective method to alter the morphology of these membranes is via polymer blending. In this study, varying compositions of Penta Block Copolymers (PBC) with two different ion-exchange capacities (IEC) of 1.0 and 2.0 were blended with poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) to create 2wt% homogenous solution-cast membranes in chloroform. When compared to unmodified PBC(1.0) and PBC(2.0), unmodified PPO membrane possesses higher thermal decomposition temperatures, and as the PPO blend ratio increased, the decomposition temperature of PBC(1.0)-PPO and PBC(2.0)-PPO increased. In addition, water uptake (WU) studies revealed that WU% of the blend decreases as the PPO blend ratio increases. When hydrophobic PPO blends with the hydrophilic sulfonated ionomers, the ionic channels are hindered, lowering the WU%. These results are further supported by the proton conductivity studies, which portray a similar trend in ion conductivity to the water uptake. However, it is interesting that as the temperature increases from 30°C to 70°C, the proton conductivity of PBC (1.0) membranes blended with PPO in the ratio of 90:10 and 80:20 exhibits 65% more conductivity than that of pure PBC (1.0). This behavior may be attributed to morphological transitions within the membrane as the temperature increases. In conclusion, the study shows that the composition of sulfonated and unsulfonated polymer blend components significantly alters the membrane's intermolecular interactions, changing the membrane's durability and transport properties.

Ion conduction and durability of penta block copolymer blends

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ACS Fall 2022

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