Phosphoric acid (PA)-doped polybenzimidazole (PBI) proton exchange membranes have received attention because of their good mechanical properties, moderate gas permeability, and superior proton conductivity under high temperature operation. Among PBI-based film membranes, nanofibrous membranes withstand to higher strain because of strongly oriented polymer chains while exhibiting higher specific surface area with increased number of proton-conducting sites.In this study, PBI electrospun nanofibers were produced and doped with PA to operate as high temperature proton exchange membrane, while changes in proton conductivity and morphologies were monitored. Proton conductive PBI nanofiber membranes by using the process parameters of 15 kV and 100 μL/h at 15 wt% PBI/dimethylacetamide polymer concentration were prepared by varying PA doping time as 24, 48, 72, and 96 hours. The morphological changes associated with PA doping addressed that acid doping significantly caused swelling and 2-fold increase in mean fiber diameter. Tensile strength of the membranes is found to be increased by doping level, whereas the strain at break (15%) decreased because of the brittle nature of H-bond network. 72 hour doped PBI membranes demonstrated highest proton conductivity whereas the decrease on conductivity for 96-hour doped PBI membranes, which could be attributed to the morphological changes due to H-bond network and acid leaking, was noted. Overall, the results suggested that of 72-hour doped PBI membranes with proton conductivity of 123 mS/cm could be a potential candidate for proton exchange membrane fuel cell. Figure 1) is capable of absorbing acids (pKa~5.5), which is essential to be used in fuel cell membranes and other protonconducting applications. 2 To overcome the drawbacks of the low-temperature proton exchange membrane fuel cell (PEMFC) such as CO catalyst poisoning, necessity of humidification, heat management, and low diffusion rates of protons, PBI-based membranes were preferred because of their superior proton conductivity particularly both at high temperatures 3-5 and at 0% relative humidity. 6 Phosphoric acid-doped polybenzimidazole membranes were first successfully prepared by Wainright et al. 7,8 These membranes were recommended as electrolyte for high-temperature proton exchange membrane fuel cell (HT-PEMFC) operating at temperatures of up to 200°C. 8,7 They also exhibited good mechanical properties and low gas permeability [9][10][11] compared to water-containing membranes including Nafion whose proton conductivity decreases with increased temperature because of the evaporation of H 2 O molecules. 12 In addition, the results showed that an increase in doping level resulted in better proton conductivity and so more efficient HT-PEMFC performance. 7,13 After blended with PA, PBI films might suffer from deterioration because of the slow elution of water-soluble PA, when the vapor was produced. 14 Moreover, it was reported that these film membranes also sacrificed the

Carbon nanotubes (CNTs) have been explored to increase the mechanical properties and electrical conductivity of polymeric fibers through compounding with polymer to be extruded into fibers. However, this route creates major challenges because CNTs have strong cohesion and tend to aggregate and precipitate due to their poor interfacial interaction with polymers. CNTs can be individualized from agglomerations to enhance the mechanical and electrical properties of polymer fibers but even so the capillary forces during solvent drying creates CNTs bundling. In this study, classical molecular dynamics (MD) simulations are used to predict and characterize CNTs-polymer interface mechanism in two different polymer matrices: polyvinyl butyral (PVB) and polystyreneco-glycidyl methacrylate (P(St-co-GMA)). The dominated interface mechanisms are discovered to shed light on CNTs dispersion in solvent based systems and to explore the prerequisites for stabilized nanofluids. Our results showed that π-stacking interactions between aromatic groups and graphene surfaces of CNTs as in P(St-co-GMA) systems, play an important role in dispersion of CNTs, whereas slight repulsions between CNTs and PVB chains lead to large morphological differences and CNTs bundles in many chain systems. Altogether, the results indicated that polymers with structures having strong interactions with the surfaces of SWNTs through π-π interactions are more effective in dispersing CNTs and caused stabilized solutions in wet fiber processing.