A new proton conducting material with a possible application as a membrane in fuel cells is synthesized. It is formed by nanocrystalline cellulose (NCC) doped with a different concentration of the imidazole molecules (Im) used as “dry” conducting species. The nanocomposites (NCC-Im) are obtained in the form of films. Their chemical composition, thermal properties, and the electric conductivity are determined by elementary and thermogravimetric analysis, differential scanning calorimetry and impedance spectroscopy methods, respectively. The nanocomposite (1.7NCC-Im) with the highest concentration of imidazole i.e. one Im per 1.7 glucose unit shows the highest electrical conductivity equal to 2.7 × 10⁻² S/m at 140 °C. This value is about five orders of magnitude higher than that of the pure NCC film at this same temperature. The important feature is that it is obtained for nanocomposite under anhydrous conditions.

Dicarboxylic acids are interesting for crystal engineering due to their ability of hydrogen bond formation. To find a relationship between the molecular structure and the properties of proton conducting materials, we synthesized two compounds of benzimidazole with dicarboxylic acids of different chain length: glutaric and pimelic acids. The structure of the compounds was determined by X-ray diffraction and compared with molecular arrangement studied by ¹³C CP/MAS NMR spectroscopy supported by Density Functional Theory computations for benzimidazole. Benzimidazole was found to form salt with glutaric acid in a 1 : 1 ratio and monoclinic layer-type structure with P2₁/n space group. Flat layers, parallel to (−102) plane, are built of glutaric acid molecules linked into rectangular-type chains by O–H⋯O bonds and benzimidazole molecules attached to the chains by N–H⋯O bonds. The molecule of the benzimidazole compound with pimelic acid contains two benzimidazole rings and one pimelic acid chain. The structure with alternating layers, built of two groups of benzimidazole dimers and layers of pimelic acid chains, belongs to P2₁/n space group. The acid layers are built of pimelic acid molecules linked by O–H⋯O hydrogen bonds into chains parallel to [30−1] direction and the benzimidazole dimers are linked to the acid layers by N–H⋯O bonds. Impedance spectroscopy studies in wide frequency and temperature range of pellets made of powdered compounds enabled to separate the contributions of crystalline and grain boundary parts to the electric conductivity. The conductivity (averaged over all directions) of the crystalline compounds of benzimidazole with glutaric and pimelic acid is characterized by activation energy of 2.5 eV and 1.6 eV, respectively, which is in an agreement with the hydrogen bond network in the materials.