Nafion®-based polymer actuators with ionic liquids as solvent incorporated at room temperature
Nafion®-based polymer actuators with ionic liquids as solvent incorporated at room temperature
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DOI：
10.1063/1.3204961
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发表时间：
2009-09-01
影响因子：
3.2
通讯作者：
Tsuchitani, Shigeki
中科院分区：
文献类型：
--
作者：
Kikuchi, Kunitomo;Tsuchitani, Shigeki
以离子液体为溶剂，在室温下将反离子交换到离子液体中，制备了Nafion(R)基离子聚合物-金属复合材料。在室温下，IPMC只需在去离子水和离子液体的混合物中浸泡48h即可进行离子交换，制备的IPMC的弯曲曲率与传统的离子液体IPMC相同或更大，由离子液体与离子液体在100℃左右的高温下交换而成，并且在空气中长期稳定运行，180min的弯曲曲率波动小于21%。在本方法中，离子液体的有效离子交换可能是由于离子液体在Nafion(R)膜中吸附水而加快了离子液体向IPMC中的扩散速度。令人惊讶的是，在含有离子液体1-乙基-3-甲基咪唑四氟硼酸盐(BMIBF4)、1-丁基-3-甲基咪唑四氟硼酸盐(BMIBF4)和1-丁基-3-甲基咪唑六氟磷酸盐(BMIPF6)的IPMC中，含有水不溶的BMIPF6的IPMC比含有水可混溶的BMIBF4的IPMC具有更大的弯曲曲率。这可能是由于BMIPF6有效地结合到IPMC中，因为BMIPF6与IPMC的亲和力高于与水和BMIPF6混合物中的水的亲和力。对离子液体IPMCs驱动电流的复阻抗和阶跃电压响应的测量表明，在高于约0.1 Hz的频率范围内，它们由Nafion(R)的膜电阻串联电路和金属电极上的双电层电容与Nafion(R)的膜电容并联组合的等效电路表示。三种离子液体IPMC弯曲曲率大小的不同主要是由于膜电阻的不同导致弯曲响应速度的不同。
Nafion (R)-based ionic polymer-metal composites (IPMCs), with ionic liquids as solvent, were fabricated by exchanging counterions to ionic liquids at room temperature. Ion exchange is performed by only immersing IPMC in a mixture of de-ionized water and ionic liquids at room temperature for 48 h. The fabricated IPMCs exhibited a bending curvature the same as or larger than that of conventional IPMCs with ionic liquids, formed by ion exchange to ionic liquids at an elevated temperature up to about 100 degrees C, and also had long-term stability in operation in air, with a fluctuation smaller than 21% in bending curvature during a 180 min operation. The effective ion exchange to ionic liquids in the present method is probably due to an increase in diffusion speed of ionic liquids into IPMC by adsorption of water in a Nafion (R) membrane. It is a surprise that among IPMCs with ionic liquids 1-ethyl-3-methyl-imidazolium tetrafluoroborate, 1-buthyl-3-methyl-imidazolium tetrafluoroborate (BMIBF4), and 1-buthyl-3-methyl-imidazolium hexafluorophosphate (BMIPF6), IPMC with water-insoluble BMIPF6 exhibited a larger bending curvature than that IPMC with water-miscible BMIBF4. This might be due to effective incorporation of BMIPF6 into IPMC, since BMIPF6 has a higher affinity with IPMC than with water in the mixture of water and BMIPF6. From measurements of complex impedance and step voltage response of the driving current of IPMCs with ionic liquid, they are expressed by an equivalent circuit of a parallel combination of a serial circuit of membrane resistance of Nafion (R) and electric double layer capacitance at metal electrodes, with membrane capacitance of Nafion (R), in a frequency range higher than about 0.1 Hz. The difference in magnitude of bending curvature in three kinds of IPMCs with ionic liquids is mainly due to the difference in bending response speed coming from the difference in the membrane resistance.