Highly Selective Polymer Electrolyte Membranes from Reactive Block Polymers
Highly Selective Polymer Electrolyte Membranes from Reactive Block Polymers
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DOI：
10.1021/ma901272s
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发表时间：
2009-08-25
期刊：
影响因子：
5.5
通讯作者：
Hillmyer, Marc A.
中科院分区：
文献类型：
--
作者：
Chen, Liang;Hallinan, Daniel T., Jr.;Hillmyer, Marc A.
采用原子转移自由基聚合法合成了一系列反应性嵌段聚合物，即苯乙烯-均苯乙烯-聚苯乙烯磺酸正丙酯（PNS PSSP）。制备含有PNS-PSSP、环烯烃二环戊二烯和/或环辛烯和第二代Grubbs复分解催化剂的溶液，流延成薄膜，并使其在室温下通过开环复分解聚合机理固化。固化膜上的小角X射线散射（SAXS）数据与包含限制在复分解反应性PNS嵌段和聚（环烯烃）的交联基质中的PSSP域的纳米结构材料的形成一致。这些膜中的PSSP相通过丙磺酸酯的水解转化为磺酸形式。用小角X射线散射和透射电子显微镜对所得交联聚合物电解质膜进行了表征。在这些膜中，具有由连续和机械坚固相支撑的磺酸相的连续域的双连续形态是明显的。PNS-PSSP嵌段聚合物的分子量控制域的大小，并且膜的机械性能可以通过所使用的环烯烃的选择来调节。PEM表现出明显的机械和热鲁棒性。此外，所有PEM中的质子传导率与在Nafion中观察到的质子传导率相似（最大。燃料电池中经常使用的PEM）。选择质子交换膜表现出显着较低的甲醇渗透比全氟磺酸，同时保持高饱和质子电导率，这可能会导致更高的直接甲醇燃料电池的功率密度。这种用于制备PEM的反应性嵌段聚合物策略是有吸引力的，这是由于双连续结构的容易形成、域尺寸的容易控制以及独立地控制基质材料的机械和溶胀性质的能力。
A series of reactive poly(norbornenylethylstyrene-s-styrene)-poly(n-propyl-p-styrenesulfonate) (PNS-PSSP) block polymers were prepared by atom transfer radical polymerization. Solutions containing PNS-PSSP, the cyclic olefins dicyclopentadiene and/or cyclooctene, and the second-generation Grubbs metathesis catalyst were prepared, cast as thin films, and allowed to cure at room temperature by a ring-opening metathesis polymerization mechanism. Small-angle X-ray scattering (SAXS) data on cured Films were consistent with the formation of nanostructured materials containing PSSP domains confined in a cross-linked matrix of the metathesis-reactive PNS block and the poly(cyclic olefins). The PSSP phase in these films was converted into the sulfonic acid form by hydrolysis of the propyl sulfonate ester. The resulting crosslinked polymer electrolyte membranes (PEMs) were characterized by SAXS and transmission electron microscopy. A bicontinuous morphology with continuous domains of the sulfonic acid phase supported by a continuous and mechanically robust phase was evident in these films. The molecular weight of the PNS-PSSP block polymer controlled the domain sizes, and the mechanical properties of the membranes could be tuned through the choice of cyclic olefins used. The PEMs exhibited pronounced mechanical and thermal robustness. Furthermore, proton conductivities in all the PEMs were similar to those observed in Nafion (the most. frequently used PEM in fuel cells) at high humidity. Select PEMs showed significantly lower methanol crossover than Nafion while maintaining high-saturated proton conductivities, which could result in higher direct methanol fuel cell power densities. This reactive block polymer strategy for the preparation of PEMs is attractive due to the ready formation of bicontinuous structures, the facile control of domain size, and the ability to independently control mechanical and swelling properties of the matrix material.