Probing microphase separation and proton transport cooperativity in polymer-tethered 1H-tetrazoles

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2014-11, Vol.52 (21), p.1375-1387
• Main Authors: Chaloux, Brian L., Ricks-Laskoski, Holly L., Miller, Joel B., Saunders, Kaitlin M., Hickner, Michael A.
• Format: Article
• Language: English
• Subjects: 1H-tetrazole; Analogies; Applied sciences; carboxylic acid; Carboxylic acids; charge carrier density; Chemical modifications; Chemical reactions and properties; Drying; Exact sciences and technology; microphase separation; Organic polymers; Origins; Phase separation; Physicochemistry of polymers; polyelectrolytes; proton conductor; proton mobility; Relative humidity; Separation; Uptakes
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23573

ABSTRACT 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 pKas, 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. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1375–1387 To elucidate the origins of proton conductivity and microphase separation in a styrenic 1H‐tetrazole polymer (PS‐Tet), its physical and conductive properties are compared with a carboxylic acid analog (PS‐HA). Although exhibiting similar aqueous properties, 1H‐tetrazole and carboyxlic acid give rise to fundamentally different physics and conductivity in polymers containing them. Despite similar polymer water uptake, these differences extend to both anhydrous and hydrated conditions.