We report successful synthesis of three types of pyridine bridged tetraamine (PyTAB) monomers namely PyTAB-COOH, PyTAB-OH and PyTAB-CF₃ where additional functional groups –COOH, -OH, and –CF₃, respectively have been tagged in the parent PyTAB for the synthesis of soluble polybenzimidazoles (PBI). These newly designed PyTAB monomers were polymerized with varieties of dicarboxylic acids to yield series of pyridine bridged PBIs (PyPBIs). Thermal stability, mechanical strength (storage modulus) and glass transition temperature of PyPBIs were found to be influenced by the presence of additional functionalities in the PyTAB monomer and attributed to the hydrogen bonding capability and hydrophobicity of the functional groups. Newly synthesized PyPBIs displayed greater stability in phosphoric acid (PA) when compared with the non-functionalized PyPBIs, former is stable up to 85% PA whereas later is only up to 60% PA. The increased intermolecular interactions and possibility of crosslinking between the polymer chains owing to the presence of functional groups in the functionalized PyPBIs caused the increased stability in PA. The significantly low swelling (<1%) in water of PyPBIs considered to be a new benchmark of water swelling of PBI based polymers. Proton conductivities of PA loaded PyPBI were considerably higher than the conventional PBIs and non-functionalized PyPBIs and also depends on the functionality, structure of DCA and solvent used to make membranes. Functionalized PyPBIs (current study) showed conductivity as high as 0.12 S/cm whereas non-functionalized PyPBIs usually displayed conductivity around 0.01 S/cm. Porous and well connected network morphology of formic acid treated PyPBI membrane were attributed to the high PA loading and conductivity of PyPBI membrane.

我们报告成功合成了三种类型的吡啶桥联四胺（PyTAB）单体，即PyTAB-COOH，PyTAB-OH和PyTAB-CF ₃，其中另外的官能团为-COOH，-OH和-CF ₃分别在母体PyTAB中进行了标记，以合成可溶性聚苯并咪唑（PBI）。这些新设计的PyTAB单体与各种二元羧酸聚合，生成一系列吡啶桥联的PBI（PyPBI）。发现PyPBI的热稳定性，机械强度（储能模量）和玻璃化转变温度受PyTAB单体中其他官能团的存在影响，并且归因于氢键合能力和官能团的疏水性。与未官能化的PyPBI相比，新合成的PyPBI在磷酸（PA）中显示出更高的稳定性，前者在高达85％的PA下稳定，而后者仅在60％的PA下稳定。由于官能化的PyPBI中存在官能团，分子间相互作用的增加和聚合物链之间交联的可能性导致了PA稳定性的提高。PyPBIs在水中的溶胀度极低（<1％），被认为是PBI基聚合物水溶胀性的新基准。负载PA的PyPBI的质子电导率明显高于常规PBI和未官能化的PyPBI，并且还取决于DCA的功能，结构和用于制膜的溶剂。功能化的PyPBIs（当前研究）显示出高达0.12 S / cm的电导率，而非功能化的PyPBIs通常显示出0.01 S / cm的电导率。