【作者】 赵成吉；

【导师】 那辉；

【作者基本信息】 吉林大学 ， 高分子化学与物理， 2008， 博士

【摘要】 采用“一锅两步法”,以不同嵌段长度的氟封端的聚芳醚酮齐聚物与生成亲水嵌段的磺化二氟二苯酮和四甲基联苯二酚共聚,合成了不同磺化度和不同嵌段长度的嵌段SPAEK共聚物。我们利用TEM和SAXS对磺化聚芳醚酮嵌段共聚物的微观形态进行了研究。相同IEC下,嵌段共聚物膜的质子传导率高于无规聚合物。另一方面,嵌段SPAEK膜的质子传导率随着离子含量和嵌段长度的增加而增大。从而,我们建立起了嵌段SPAEK膜的形貌、结构和性能之间的关系。我们接着合成了一种新型的磺化聚芳醚砜-b-聚芳醚酮多嵌段聚合物。为了克服高磺化度SPAEK膜的缺点,特别是将其应用于直接甲醇燃料电池中,我们通过溶液共混的方法制备了具有不同含量的SPEEK/PAI复合膜。更多还原

【Abstract】 Polymer exchange membrane fuel cells (PEMFCs) are the rapidly developing fifth-generation fuel cell. With the lowest working temperaturethe highest specific energy, the fastest startup, the longest service life, and the widest applications, PEMFCs have received widely investigated as a promising new power sources for vehicles and portable devices. Proton exchange membrane is a key component of the PEMFC for transferring protons from the anode to cathode as well as providing a barrier to the fuel gas cross-leaks between the electrodes. The membranes traditionally used in PEMFC are perfluorosulfonic polymers such as Dupont Nafion?. Although they show superior performance in fuel cells operating at moderate temperatures (<90oC) and high relative humidity with pure hydrogen as fuel, the high cost, low conductivity at low humidity or high temperature and high methanol permeability of Nafion? have limited their usages. Hence alternative proton exchange membrane materials are being sought. For instance, recently our groups have explored several sulfonated poly(aryl ether)s (SPAEs) for proton exchange membranes usages. Although they show very good potential usages in PEM, there still have several drawbacks to solve. (1) SPAEs with low IEC exhibited good mechanical strength and methanol resistance. However, their low proton conductivity restricts the performance in fuel cell. (2) SPAEs with high IEC exhibited superior proton conductivity. However, the brittleness of the membranes at evaluated temperatures, excessively swelling properties and the relatively high methanol crossover in membranes has limited their usages.In order to solve these problems and improve selected PEM properties, two methods were proposed in this dissertation: (1) block copolymers; (2) acid-base blend membranes.In chapter 2, block SPAEK copolymer ionomers were successfully synthesized by a two-stage process. First, the hydrophobic block with controlled length on average was prepared. And then, the monomers with desired stoichiometry were added in order to prepare and control the length of the hydrophilic block. Each block copolymer was then composed of an alternating sequence of several hydrophilic and hydrophobic blocks. Further we have characterized the structures in detail.In chapter 3, the morphology of block SPAEK membranes was detailed investigated by various measurements, including small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). As observed by TEM, spherical ionic clusters uniformly dispersed thought the random SPAEK polymer backbone matrix. The ionic cluster size was in the range of 5-15nm, which is dependent of the degree of sulfonation. On the oter hand, a large number of smaller ionic clusters (<5nm) and a certain amount of bigger ionic clusters (20-35nm) appeared for block SPAEK membranes. However, the amount of these silver clusters was less than that of random membranes. Instead, the dark colored ionic domains spreading as a cloud-like belt were also observed. These wide ionic domains were well-connected each other by a mass of bigger and smaller ionic clusters together with medium size clusters. This observation was also confirmed by the SAXS analysis. The ionomer peaks in SAXS profiles indicated the presence of large ionic domains for most of polymers. The results showed that the block copolymers exhibited larger size of ionic domains or more clearly phase-separated microstructures with the increase of ionic content and hydrophobic sequence length. Futher, we have studied the properties of the resulted block SPAEK membranes in detail. Then, the relationship between morphology and proton conductivity of block SPAEK membranes was then established according to experimental data.In chapter 4, to obtained more clear structure and more obvious phase sepation, a new series of hydrophobic-hydrophilic multiblock copolymers derived from fluorine terminated poly(arylene ether ketone) as hydrophobic blocks and phenoxide terminated sulfonated poly(arylene ether sulfone) as hydrophilic blocks were successfully synthesized and evaluated for use as proton exchange membranes (PEMs). All the hydrophobic and hydrophilic oligomers were synthesized via molecular-weight controlled step growth polymerization of the monomers. 1H NMR spectra were used as characterization tool to determine the telechelic oligomers’molecular weight and multiblock copolymer’s structure. The morphologies of multiblock copolymers were investigated by TEM, which showed they had a clear microphase-separated structure between the hydrophilic domains and hydrophobic domains. All the sulfonated poly(arylene ether sulfone)-b-poly (arylene ether ketone) copolymers can easily be cast into tough membranes and show high thermal stability. Membrane properties including ion exchange capacities (IECs), water uptake and proton conductivities were characterized for the multiblock copolymers and compared with random sulfonated poly(arylene ether)s and other multiblock copolymer membranes at similar ion exchange capacity value. This series of multiblock copolymers showed moderate conductivities up to 0.063 S/cm at 80°C with very low water uptake of 19%. Therefore, they are considered to be promising PEM materials for fuel cells.In chapter 5,highly disulfonated poly( aryl ether ether ketone)s (SPEEK-70) copolymer was synthesized via direct polymerization. To overcome the shortcomings of the SPAEK membrane with high IEC, Poly (amide imide) was blended with SPEEK-70 to improve the methanol resistance and mechanical properties. These blend membranes were characterized as a function of weight fraction of PAI in terms of ion exchange capacity (IEC), water uptake, water desorption, proton conductivity and methanol permeability in detail. Therefore, considering these results, the SPEEK/PAI blend membranes are promising for the usage in DMFC.更多还原