由4,4-Oxybis(benzoic acid)與4-硝基苯二胺合成二硝基化合物Bis(4-(2-(5-nitrobenzimidazolyl))phenyl)ether(O/IM/NO2)，再將O/IM/NO2還原成二胺單體Bis(4-(2-(5-aminobenzimidazolyl))phenyl)ether (O/IM/NH2)。由六環酸酐NTDA與含benzimidazole二胺單體，包括O/IM/NH2、2,2’-bis(2-benzimidazole)-4,4’-diaminobiphenyl (BP/IM/NH2)與1,3-diamino-5-(2-benzimidazole)benzene (m/IM/NH2)以及其他芳香族的二胺單體合成在主鏈與側基均含有benzimidazole之聚醯亞胺(PI)共聚物，其固有黏度範圍在0.94~1.87dL/g之間，均可塗佈成具韌性之薄膜，這些共聚物有好的熱安定性，於氮氣下10 %裂解溫度皆高於500℃，它們也有高的玻璃轉換溫度(Tg約在300℃)，聚合物尚未摻雜磷酸的抗張強度大於103 MPa，但是當摻雜磷酸後，薄膜受到磷酸的膨潤，機械強度會大幅下降。藉由側甲基進行交聯反應，形成交聯 PI 共聚物，交聯後 PI 共聚物因受交聯鍵結，形成高分子鏈緊密堆積，導致磷酸摻雜量下降，但仍能有足夠高的質子傳導度，並能維持好的機械性質，交聯後C3-O6BPBI2PF1.7DMB0.3濕膜抗張強度由8 MPa提升到15 MPa。本研究所合成PI共聚物在140℃時的質子傳導度幾乎都比m-PBI高，例如O7BPBI2PF1與O6BPBI2F1DMB1在140℃時之質子傳導度分別為82.5
與69.7 mS/cm皆高於m-PBI (52.7 mS/cm) ，這結果顯示導入benzimidazole環在主鏈與側基有利於提高質子傳導度，很有潛力應用於中溫型燃料電池的質子傳導膜。

Reaction of 4,4-oxybis(benzoic acid) with 4-nitro-o-phenylenediamine in polyphosphoric acid gave bis(4-(2-(5-nitrobenzimidazolyl))phenyl)ether (O/IM/NO2), which was hydrogenated to give novel monomer of bis(4-(2-(5-aminobenzimidazolyl))phenyl)ether(O/IM/NH2).
A series of copolyimides (PIs) containing main-chain and pendant benzimidazole groups were synthesized from 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA), diamines which had benzimidazole such as O/IM/NH2, 2,2 ’-bis(2-benzimidazole)-4,4’- diaminobiphenyl (BP/IM/NH2), 1,3-diamino-5- (2- benzimidazole) benzene (m/IM/NH2) and other aromatic diamines. They had inherent viscosities in the range of 0.94~1.87 dL/g, and they could form tough and flexible films. The PIs exhibited high thermal stability with 10% decomposition temperature more than 500℃ in nitrogen, and their glass transition temperature is around 300℃. These films exhibited good mechanical properties with tensile stress exceeded 103 MPa. However, the mechanical properties of PI significantly decreased when phosphoric acid doping level increased. The mechanical properties of phosphoric acid doped PIs could be improved via crosslinking reaction of methyl group, cross-linked PI would form close packing, and it led to decrease of phosphoric acid doping level, but it could still maintain high proton conductivity and high mechanical properties. The tensile strength of C3-O6BPBI2PF1.7DMB0.3 in wet state enhanced from 8 to 15 MPa after crosslinking reaction. Almost all PIs exhibited higher on proton conductivities at 140℃ than m-PBI(52.7 mS/cm). For example, the proton conductivities of O7BPBI2PF1 and O6BPBI2F1DMB1 were 82.5 and 69.7 mS/cm, respectively. Thus, these polyimides (PIs) containing benzimidazole on main chain and on pendant could be the promising materials alternative to m-PBI membrane for medium-temperature fuel cells applications because of their high proton conductivity and good oxidative stability.

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