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ABSTRACT Anion exchange membranes (AEM) are solid polymer electrolytes that facilitate ion transport in fuel cells. In this study, a polystyrene- b-poly(vinylbenzyl trimethylammonium) diblock copolymer was evaluated as potential AEM and compared with the equivalent homopolymer blend. The diblock had a 92% conversion of reactive sites with an IEC of 1.72 ± 0.05 mmol g−1, while the blend had a 43% conversion for an IEC of 0.80 ± 0.03 mmol g−1. At 50°C and 95% relative humidity, the chloride conductivity of the diblock was higher, 24-33 mS cm−1, compared with the blend, 1-6 mS cm−1. The diblock displayed phase separation on the length scale of 100 nm, while the blend displayed microphase separation (∼10 μm). Mechanical characterization of films from 40 to 90 microns thick found that elasticity and elongation decreased with the addition of cations to the films. At humidified conditions, water acted as a plasticizer to increase film elasticity and elongation. While the polystyrene-based diblock displayed sufficient ionic conductivity, the films' mechanical properties require improvement, i.e., greater elasticity and strength, before use in fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41596. [ABSTRACT FROM AUTHOR]