Theoretical Description of the Structural Characteristics of the Quaternized SEBS Anion-Exchange Membrane Using DFT,The Journal of Physical Chemistry C

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Theoretical Description of the Structural Characteristics of the Quaternized SEBS Anion-Exchange Membrane Using DFT
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2015-12-10 00:00:00 , DOI: 10.1021/acs.jpcc.5b07166
Sergio Castañeda ₁ , Rafael Ribadeneira ₁

Affiliation

For four conforming structures of the quaternized polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene membrane (QSEBS), (a) tetramethylammonium hydroxide (TMA⁺OH^–), (b) benzyltrimetylammonium hydroxide, and (c and d) QSEBS segments with 1 and 2 side chains (DBQSEBS), spatial distribution, bond distances, and charge-density profiles were obtained with density functional theory (DFT) and compared with structural simulations of DBQSEBS for two different hydration levels. Results for the TMA⁺OH^– showed that its constituent ions stay metastable in the vicinity of each other and are joined by donor–acceptor interactions. Also, simulations of the other conforming structures show that, in the absence of water, spatial distribution as well as charge-density profiles of trimethylammonium hydroxide do not change with respect to isolated TMA⁺OH^–, demonstrating that the QSEBS chain is a thermodynamically stable backbone to support the functional group, which is in agreement with the literature. When hydrated, simulations of DBQSEBS for water uptake of 4 show that there is a partial dissociation of hydroxide ions due to donor–acceptor interactions acting competitively on them. For water uptake of 6, this dissociation is completed, and hydroxide ions conform to hypercoordinated structures similar to the square-planar arrangement described for pure water medium, but with some structural differences associated with location, type, and interactions among the molecules involved.

中文翻译：

DFT对季铵化SEBS阴离子交换膜结构特征的理论描述

用于季铵化聚苯乙烯-四个符合结构块-聚（乙烯- RAN丁烯） -嵌段-聚苯乙烯膜（QSEBS）中，（a）氢氧化四甲铵（TMA ⁺ OH ^{- ），（b）}中的氢氧化benzyltrimetylammonium，以及（c和d）使用密度泛函理论（DFT）获得具有1和2个侧链的QSEBS链段（DBQSEBS），空间分布，键距和电荷密度分布图，并将其与DBQSEBS的两种不同水合水平的结构模拟进行比较。TMA ⁺ OH的结果^–结果表明，其组成离子在彼此附近保持亚稳态，并通过供体-受体相互作用而结合在一起。此外，对其他符合结构的模拟结果表明，在没有水的情况下，氢氧化三甲铵的空间分布以及电荷密度分布对于分离的TMA ⁺ OH不会发生变化^–，表明QSEBS链是支持该官能团的热力学稳定主链，这与文献一致。当水合后，DBQSEBS的吸水量为4的模拟表明，由于施主与受主之间的竞争性竞争，氢氧根离子会部分解离。对于6的吸水率，该离解完成，并且氢氧根离子符合超配位结构，类似于针对纯水介质所述的正方形平面排列，但是在结构，位置，类型和所涉及分子之间的相互作用方面存在一定的结构差异。

更新日期：2015-12-10

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