Constructing Flexible Proton Exchange Membranes Through Alternate Deposition of Kevlar Nanofibers and Polydopamine Coating Polystyrene-Block-Poly(ethylene-ran-butylene)-Block-Polystyrene

The flexible proton exchange membrane (PEM) was constructed through alternate deposition of Kevlar nanofibers and polydopamine (PDA)-coating polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) with spin coating technology. In the prepared (Kevlar/PDA@SEBS)₅ membrane, the Kevlar nanofibers could withstand the external mechanical force owing to the fiber structure, while the flexible PEM was folded or stretched. The adhesive PDA coating was formed with the self-polymerization of dopamine protected the molecular chains of SEBS and further supported the flexible PEM. The structure of PDA coating SEBS could avoid the microstructure fracture of the flexible PEM during the folding and stretching operations. Notably, the multilayered structure promoted the phosphoric acid (PA) molecules motion through reducing the ion conduction resistance. For instance, the pristine (Kevlar/PDA@SEBS)₅/PA membrane exhibited the proton conductivity of 4.11 × 10^–2 S/cm at 160 °C, which was comparable to 4.13 × 10^–2 S/cm of the folded membrane and (4.07–4.78) × 10^–2 S/cm of the stretched membranes. The stable microstructure guaranteed the stiffness, such as 4.15 MPa of the (Kevlar/PDA@SEBS)₅-fold/PA membrane and (3.50–6.34) MPa of (Kevlar/PDA@SEBS)₅-stretched/PA membranes. Furthermore, the stretched membrane possessed the long-term proton conductivity stability, which was indicative of the microstructure and component stabilities.