Probing Hydrogen Bonding and Proton Mobility in Dicyanoimidazole Monomers and Polymers

Hydrogen bonding and proton mobility are important features in many polymers. In this work, hydrogen bonding is studied in both monomers and polymers of dicyanoimidazoles using infrared and solid-state NMR spectroscopy and polymer viscosity studies. Hydrogen bonding accounts for an unusual complexity in the nitrogen−hydrogen stretching region of the infrared spectra. The influence of hydrogen bonding on properties was observed in several dicyanoimidazole polymers through polymer viscosity studies and estimation of Mark−Houwink parameters. The Mark−Houwink a value decreases, representing a less stiff chain, in poly(1-methyl-2-vinyl-4,5-dicyanoimidazole) compared to poly(2-vinyl-4,5-dicyanoimidazole) because hydrogen bonding is eliminated. By dissolving poly(2-vinyl-4,5-dicyanoimidazole) in NH3(aq), a polymer electrolyte results. Although hydrogen bonding is eliminated, electronic repulsions contribute to an increase in a or chain stiffness. Proton mobility in dicyanoimidazole polymers was studied with an innovative solid-state NMR technique using double-quantum (DQ) filtering and fast magic angle spinning (MAS = 30 kHz). Using this approach, several types of hydrogen bonds were identified and proton mobility in poly(2-vinyl-4,5-dicyanoimidazole) was detected.