Ciftcioglu Gokcen A, Frank Curtis W
Department of Chemical Engineering, Marmara University, Istanbul 34722, Turkey.
Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA.
Molecules. 2021 Apr 8;26(8):2143. doi: 10.3390/molecules26082143.
Proton exchange membranes (PEMs) suffer performance degradation under certain conditions-temperatures greater than 80 °C, relative humidity less than 50%, and water retention less than 22%. Novel materials are needed that have improved water retention, stability at higher temperatures, flexibility, conductivity, and the ability to function at low humidity. This work focuses on polyimide-poly(ethylene glycol) (PI-PEG) segmented block copolymer (SBC) membranes with high conductivity and mechanical strength. Membranes were prepared with one of two ionic liquids (ILs), either ethylammonium nitrate (EAN) or propylammonium nitrate (PAN), incorporated within the membrane structure to enhance the proton exchange capability. Ionic liquid uptake capacities were compared for two different temperatures, 25 and 60 °C. Then, conductivities were measured for a series of combinations of undoped or doped unannealed and undoped or doped annealed membranes. Stress and strain tests were performed for unannealed and thermally annealed undoped membranes. Later, these experiments were repeated for doped unannealed and thermally annealed. Mechanical and conductivity data were interpreted in the context of prior small angle X-ray scattering (SAXS) studies on similar materials. We have shown that varying the compositions of polyimide-poly(ethylene glycol) (PI-PEG) SBCs allowed the morphology in the system to be tuned. Since polyimides (PI) are made from the condensation of dianhydrides and diamines, this was accomplished using components having different functional groups. Dianhydrides having either fluorinated or oxygenated functional groups and diamines having either fluorinated or oxygenated diamines were used as well as mixtures of these species. Changing the morphology by creating macrophase separation elevated the IL uptake capacities, and in turn, increased their conductivities by a factor of three or more compared to Nafion 115. The stiffness of the membranes synthesized in this work was comparable to Nafion 115 and, thus, sufficient for practical applications.
质子交换膜（PEMs）在某些条件下会出现性能下降，这些条件包括温度高于80°C、相对湿度低于50%以及保水率低于22%。因此需要新型材料，这些材料应具有更好的保水性能、在较高温度下的稳定性、柔韧性、导电性以及在低湿度环境下的功能。这项工作聚焦于具有高导电性和机械强度的聚酰亚胺-聚（乙二醇）（PI-PEG）嵌段共聚物（SBC）膜。通过将两种离子液体（ILs）之一，即硝酸乙铵（EAN）或硝酸丙铵（PAN），掺入膜结构中来制备膜，以增强质子交换能力。比较了在25°C和60°C这两种不同温度下的离子液体吸收容量。然后，对一系列未掺杂或掺杂的未退火膜以及未掺杂或掺杂的退火膜的组合进行电导率测量。对未退火和热退火的未掺杂膜进行了应力和应变测试。随后，对掺杂的未退火和热退火膜重复进行这些实验。在先前对类似材料进行的小角X射线散射（SAXS）研究的背景下解释了机械性能和电导率数据。我们已经表明，改变聚酰亚胺-聚（乙二醇）（PI-PEG）SBCs的组成可以调节体系中的形态。由于聚酰亚胺（PI）由二酐和二胺缩合而成，这是通过使用具有不同官能团的组分来实现的。使用了具有氟化或氧化官能团的二酐以及具有氟化或氧化二胺的二胺，以及这些物质的混合物。通过形成宏观相分离来改变形态提高了离子液体的吸收容量，进而使其电导率相比Nafion 115提高了三倍或更多。在这项工作中合成的膜的刚度与Nafion 115相当，因此足以用于实际应用。
