Synergistic Increase in Ionic Conductivity and Modulus of Triblock Copolymer Ion Gels
Synergistic Increase in Ionic Conductivity and Modulus of Triblock Copolymer Ion Gels
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DOI：
10.1021/acs.macromol.5b00882
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发表时间：
2015-07-28
期刊：
影响因子：
5.5
通讯作者：
Lodge, Timothy P.
中科院分区：
文献类型：
--
作者：
Tang, Boxin;White, Scott P.;Lodge, Timothy P.
由ABA三嵌段聚合物和离子液体(IL)形成的离子凝胶最近引起了人们的极大关注。由聚苯乙烯-b-聚甲基丙烯酸甲酯-b-聚苯乙烯(SMS)和聚苯乙烯-b-聚氧乙烷-b-聚苯乙烯(SOS)和IL-1-乙基-3-甲基咪唑双(三氟甲基磺酰亚胺)([EMI][TFSI])三嵌段聚合物制备的离子凝胶具有高离子导电性、高电容和良好的机械完整性，已成功地应用于薄膜晶体管的介质层。然而，吸水会对电介质层的稳定性产生负面影响，并导致电击穿。因此，这两种聚合物的首选聚合物是SMS。然而，PMMA的高玻璃化转变温度(T-g)限制了SMS聚合物的可用浓度，以确保与SOS离子凝胶的离子导电性相当；这种限制将凝胶的模数限制在约10(3)Pa.在这项工作中，我们开发了一种新的ABA三嵌段离子凝胶体系，该体系以聚丙烯酸乙酯(PEA)为中间嵌段，具有较低的玻璃化温度和疏水性。中间块的低T-g确保了所得到的离子凝胶在聚合物浓度高达50wt%时的离子导电性与SOS离子凝胶相当，这相对于目前使用的SMS离子凝胶是一个显著的改进。此外，在聚合物浓度不变的情况下，通过减小中间嵌段的尺寸，离子凝胶的模数和离子电导率协同增加。这种有趣和违反直觉的效应反映了中部区块的数密度和链伸展同时增加，同时伴随着传导阶段中区块浓度的净减少。我们证明了与SOS离子凝胶相比，用SEA离子凝胶制成的电解液门控晶体管(EGTS)在环境潮湿条件下具有更好的稳定性。
Ion gels formed with ABA triblock polymers and ionic liquids (IL) have recently attracted significant attention. Because of their high ionic conductivity, high capacitance, and good mechanical integrity, ion gels prepared from triblock polymers of polystyrene-b-poly(methyl methacrylate)-b-polystyrene (SMS) and polystyrene-b-poly(ethylene oxide)-b-polystyrene (SOS) and an IL 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]) have been successfully applied as the dielectric layer in thin film transistors. However, water absorption can negatively affect the stability of the dielectric layer and lead to electrical breakdown. Consequently, the preferred polymer of these two is SMS. However, the high glass transition temperature (T-g) of PMMA limits the usable SMS polymer concentration in order to ensure comparable ionic conductivity to that of SOS ion gel; this constraint limits the modulus of the gel to about 10(3) Pa. In this work, we developed a new ABA triblock ion gel system using poly(ethyl acrylate) (PEA) as a low T-g and hydrophobic midblock. The low T-g of the midblock ensures the ionic conductivity of the resulting ion gels is comparable to that of SOS ion gels at polymer concentrations up to 50 wt %, which is a significant improvement relative to the currently used SMS ion gels. Additionally, by decreasing the size of the midblock at constant polymer concentration, the modulus and ionic conductivity of the ion gels increase synergistically. This interesting and counterintuitive effect reflects the concurrent increase in the number density and chain stretching of midblocks, accompanied by a net reduction in midblock concentration within the conducting phase. We demonstrate that electrolyte gated transistors (EGTs) made with SEAS ion gels have improved stability under ambient humid conditions in comparison to those made with SOS ion gels.