Non‐Fluorinated Functional Polyolefin for Puncture‐Resistant and Self‐Healable Proton Exchange Membranes of Fuel Cells

The development of puncture‐resistant and self‐healing proton exchange membranes (PEMs) is vital for enhancing fuel cells' (FCs) durability and safety; however, it remains a formidable challenge. Herein, we report a non‐fluorinated polyolefin‐based PEM that integrates autonomous self‐healing, puncture resistance, high gas barrier, and exceptional overall durability in FC applications. The polymers are prepared through rare‐earth‐catalyzed selective polymerization of isoprene, partial hydrogenation, thiol‐ene click chemistry, and oxidation, yielding a sulfonic acid‐functionalized polyolefin. The main chain structure of polymers features rigid poly(3‐methyl‐1‐butene) segments—derived from 3,4‐polyisoprene units—and soft ethylene‐ alt ‐propylene sequences—originating from cis ‐1,4‐polyisoprene units. The nanoscale microphase separation between these hard and soft segments provides exceptional mechanical robustness and self‐healing capability, while the aggregation of sulfonic acid groups creates efficient proton transport pathways. The resulting membrane achieves high through‐plane proton conductivity of 1.0 × 10 − 2 S cm − 1 and in‐plane conductivity of 6.4 × 10 − 1 S cm − 1 at 80°C and 100% RH. Under simulated FC operating conditions, the material autonomously heals mechanical damage, fully recovering its tensile strength, proton conductivity, gas barrier properties, and FC performance. This work establishes a versatile strategy for creating high‐performance, non‐fluorinated PEMs with enhanced safety and prolonged service life.