1H-Tetrazoles possess the lowest pKa within the azole family of nitrogen-containing heterocycles, making them attractive amphoteric moieties for anhydrous proton conduction. The synthesis of a styrenic, random coil polymer with pendent C-substituted 1H-tetrazoles is described in detail. This facile route results in a polymer containing free proton-bearing tetrazoles, limits side reactions, and proceeds using low polarity, halogenated solvents (e.g., 1,2-dichlorobenzene or chlorobenzene), which improve solubility during tetrazole cyclization. The resulting polymer, when probed by NMR spectroscopy and elemental analysis, had no measurable salt content, ensuring accurate proton conductivity measurements. Utilizing interdigitated electrodes (IDEs) in conjunction with electrochemical impedance spectroscopy (EIS), undoped anhydrous proton conductivities were measured to be as high as 10-5 S cm -1 at 120 °C. This weakly acidic, 1H-tetrazole-bearing polymer is thermally stable to 210 °C, possesses two distinct glass transitions (Tg) at 49 and 74 °C, and exhibits surprisingly low water uptake, despite its acidic and amphoteric nature. Reduction of Tgs, achieved by synthesis of low molecular weight poly(4-vinylphenol) via acid polymerization, shows a minimal dependence of anhydrous proton conductivity on backbone motion.
All Science Journal Classification (ASJC) codes
- Organic Chemistry
- Polymers and Plastics
- Inorganic Chemistry
- Materials Chemistry