10.1021/acsomega.0c01735.s001 Yemineni S L V Narayana Yemineni S L V Narayana Takefumi Yoshida Takefumi Yoshida Manas Kumar Bera Manas Kumar Bera Sanjoy Mondal Sanjoy Mondal Masayoshi Higuchi Masayoshi Higuchi Ni(II)-Based Metallosupramolecular Polymer with Carboxylic Acid Groups: A Stable Platform for Smooth Imidazole Loading and the Anhydrous Proton Channel Formation American Chemical Society 2020 Ni scanning electron microscopy measurement loading powder X-ray diffraction proton conduction pathway formation Smooth Imidazole Loading imidazole molecules Anhydrous Proton Channel Formation -9H polyNi-Im polyNi carboxylic acid groups polymer 2020-06-13 00:13:23 Journal contribution https://acs.figshare.com/articles/journal_contribution/Ni_II_-Based_Metallosupramolecular_Polymer_with_Carboxylic_Acid_Groups_A_Stable_Platform_for_Smooth_Imidazole_Loading_and_the_Anhydrous_Proton_Channel_Formation/12476459 The Ni­(II)-based metallosupramolecular polymer with carboxylic acid groups (<b>polyNi</b>) was synthesized via a 1:1 complexation of Ni­(II) salt with (4,4′-(9,9-dihexyl-9H-fluorene-2,7-diyl)­bis­(pyridine-2,6-dicarboxylic acid) for the first time. The divalent state of Ni­(II) in the polymer was confirmed by the X-ray absorption fine structure analysis. Smooth loading of imidazole molecules into <b>polyNi</b> proceeded with the help of the carboxylic acid groups to form the imidazole-loaded <b>polyNi</b> (<b>polyNi-Im</b>). Thermogravimetric analysis of <b>polyNi-Im</b> revealed that approximately three imidazole molecules were incorporated per repeating unit of <b>polyNi</b>. The Fourier transform infrared spectrum of <b>polyNi-Im</b> showed a new peak at 3219 cm<sup>–1</sup>, which shows an ∼73 cm<sup>–1</sup> enhancement to −N–H of pristine imidazole. The peak suggests the formation of an imidazolium cation in the polymer. Powder X-ray diffraction indicated no degradation of the polymer structure during the imidazole loading because the diffraction pattern of <b>polyNi-Im</b> was almost the same as that of <b>polyNi</b> except for the presence of peaks corresponding to the imidazole molecules. Interestingly, the scanning electron microscopy measurement showed a large morphological change to uniform spherical particles by loading imidazole to the polymer. <b>PolyNi-Im</b> exhibited good proton conductivity (1.05 × 10<sup>–2</sup> mS/cm) at a high temperature (120 °C), which is around 7 orders of magnitude higher than that of pristine <b>polyNi</b> because of the proton conduction pathway formation along the polymer chains by the incorporated imidazole molecules.