Molecular dynamics simulation on effect of different carboxylic acid group contents on norbornene derivatives proton exchange membranes bearing bifunctional groups

A bifunctional group proton exchange membrane(PEM) was constructed in this paper with sulfonic and carboxylic acid groups based on polynorbornenes on the software platform of Material Studio (MS). The effect on the properties of PEM were studied by changing the different proportion of three structural units 4-(bicyclo[2.2.1] hept-5-en-2-yl) benzene-1-sulfonylchloride (NBSC), dimethyl 8, 9, 10-rinorborn-5-ene-2, 3-dicarboxylate (DCNM) and DCNM-N. Meanwhile, the microscopic structure of the membranes and the transport properties of the small molecules were analyzed. The result shows that the MSD of H₂O as well as H₃O⁺and diffusion coefficients augment gradually with the reducing of carboxylic acid group contents which are the results of the hydrogen bonds interaction among the different components. Besides, under the synergistic action of sulfonic acid and carboxylic acid at 298 K, the proton conductivitise of the three proton exchange membranes are 22.75, 46.14 and 56.77 mS·cm^-1 respectively which indicates that proton conductivity rises with the aggrandizement of the number of carboxylic acid group, while the growth rate increases first and then decreases.