Synthesis of Aromatic Anion Exchange Membranes by Friedel–Crafts Bromoalkylation and Cross-Linking of Polystyrene Block Copolymers,Macromolecules

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Synthesis of Aromatic Anion Exchange Membranes by Friedel–Crafts Bromoalkylation and Cross-Linking of Polystyrene Block Copolymers
Macromolecules ( IF 5.1 ) Pub Date : 2019-02-20 00:00:00 , DOI: 10.1021/acs.macromol.8b02355
Jong Yeob Jeon , Sungmin Park , Junyoung Han , Sandip Maurya ₁ , Angela D. Mohanty , Ding Tian , Nayan Saikia ₂ , Michael A. Hickner ₂ , Chang Y. Ryu , Mark E. Tuckerman _{3,

4,

5} , Stephen J. Paddison ₆ , Yu Seung Kim ₁ , Chulsung Bae

Affiliation

Elastomeric anion exchange membranes (AEMs) were prepared by acid-catalyzed Friedel–Crafts alkylation of the polystyrene block of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) using bromoalkylated tertiary alcohols and triflic acid as a catalyst, followed by amination with trimethylamine. This simple one-step bromoalkylation allowed convenient control of both the degree of functionalization and cation tether length by changing the molar ratio and the structure of the bromoalkylated tertiary alcohol. The resulting quaternary ammonium-functionalized ionic triblock SEBS copolymers showed a microphase-separated morphology on the 35 nm length scale. A series of AEMs with different ion exchange capacities and ion tether lengths were systematically investigated by comparing swelling and anion conductivity. Because the SEBS AEMs showed high swelling and low dimensional stability in water due to the rubbery nature of SEBS, the hard segment PS units were cross-linked by 1,6-hexanediamine for practical use. The cross-linking of SEBS AEMs reduced water uptake significantly (e.g., 155% vs 28%) and enhanced their mechanical properties. Because the backbone of the SEBS AEMs are composed of all carbon–carbon bonds, they showed good alkaline stability, preserving their IEC and OH^– conductivity after testing in a 1 M NaOH solution at 80 °C for 500 h. Alkaline membrane fuel cell performance was evaluated with the cross-linked SEBS AEM, and a peak power density of 520 mW/cm² was achieved at 60 °C under H₂/O₂ conditions.

中文翻译：

Friedel-Crafts溴代烷基化和聚苯乙烯嵌段共聚物的交联合成芳族阴离子交换膜

弹性体阴离子交换膜（AEMs ）是通过溴代烷基叔醇和三氟甲磺酸作为酸催化的聚苯乙烯-b-聚（乙烯-共-丁烯）-b-聚苯乙烯（SEBS）聚苯乙烯嵌段的酸催化Friedel-Crafts烷基化制备的催化剂，然后用三甲胺胺化。这个简单的一步bromoalkylation允许官能化和阳离子系链长度的两个程度的方便的控制通过改变摩尔比和bromoalkylated的结构叔酒精。所得季铵官能化的离子三嵌段SEBS共聚物在35 nm的长度范围内显示出微相分离的形态。通过比较溶胀和阴离子电导率，系统地研究了一系列具有不同离子交换容量和离子束缚长度的AEM。由于SEBS的橡胶性质，SEBS AEM在水中显示出高溶胀度和低尺寸稳定性，因此，在实际应用中，硬链段PS单元通过1,6-己二胺交联。SEBS AEM的交联显着降低了吸水率（例如155％对28％），并增强了它们的机械性能。由于SEBS的AEM的主干是由所有的碳-碳键的，他们表现出良好的碱性稳定，维护他们的IEC和OH ^-在80°C的1 M NaOH溶液中测试500小时后的电导率。用交联的SEBS AEM评价碱性膜燃料电池的性能，在60℃，H ₂ / O ₂条件下，峰值功率密度为520mW / cm ²。

更新日期：2019-02-20

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