Probing Microphase Separation and Proton Transport Cooperativity in Polymer-Tethered 1H-Tetrazoles

To elucidate the driving forces for phase separation and proton conductivity in polystyrenic alkoxy 1H-tetrazole (PS-Tet), an analogous polystyrenic alkoxy carboxylic acid (PS-HA) was synthesized and the conductivity and chain dynamics of both materials measured. Proton and polymer motions illustrate dramatic differences in the nonaqueous behavior of carboxylic acids and 1H-tetrazoles, belying similarities in their aqueous properties. Exceptional interactions between 1H-tetrazoles drive phase separation not observed in PS-HA or reported for other azole-containing homopolymers. PS-HA and PS-Tet exhibit both dry (0% relative humidity) and hydrated proton dissociations proportional to their aqueous pK(a)s, with residual water acting as the proton acceptor in both polymers. While water is the sole contributor to mobility in PS-HA, PS-Tet exhibits dynamic interactions with water allowing 1H-tetrazole moieties to contribute to proton conduction even in the hydrated state. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1375-1387