Surface-Induced Ordering Depresses Through-Film Ionic Conductivity in Lamellar Block Copolymer Electrolytes
Surface-Induced Ordering Depresses Through-Film Ionic Conductivity in Lamellar Block Copolymer Electrolytes
复制标题
表面诱导有序化降低了层状嵌段共聚物电解质的透膜离子电导率
DOI：
10.1021/acsmacrolett.0c00039
复制
发表时间：
2020
影响因子：
7.015
通讯作者：
Stein, Gila E.
中科院分区：
文献类型：
--
作者：
Coote, Jonathan P.;Kinsey, Thomas;Street, Dayton P.;Kilbey, S. Michael;Sangoro, Joshua R.;Stein, Gila E.
基于聚合物离子液体（pil）的层状嵌段共聚物在电化学器件中具有广阔的应用前景。然而，这些体系通常表现出结构各向异性，从而降低了透膜离子电导率。这项工作假设结构各向异性是表面诱导有序的结果，其中电极上一个块的优先吸附驱动了片层的短程堆叠。用聚苯乙烯（PS）和聚（1-（2-丙烯酰氧乙基）-3-丁基咪唑双（三氟甲烷磺酰）亚胺）（PIL）的层状二嵌段共聚物考察了这一点。块状PS-PIL结构由随机取向的层状晶粒组成。然而，在PS-PIL薄膜中（100-400 nm），片层与薄膜平面垂直堆叠，当制备的薄膜厚度与自然片层周期不匹配时，会出现孤岛/空穴。这两种特性都是众所周知的表面优先润湿的结果。厚PS-PIL薄膜（50-100 μm）的离子电导率在平面内比平面内高约20倍，与薄膜内部随机取向的片层和电极表面高度取向的片层混合结构相一致。因此，为了充分优化嵌段共聚物电解质的性能，考虑表面相互作用对结构域排序的影响是很重要的。
Lamellar block copolymers based on polymeric ionic liquids (PILs) show promise as electrolytes in electrochemical devices. However, these systems often display structural anisotropy that depresses the through-film ionic conductivity. This work hypothesizes that structural anisotropy is a consequence of surface-induced ordering, where preferential adsorption of one block at the electrode drives a short-range stacking of the lamellae. This point was examined with lamellar diblock copolymers of polystyrene (PS) and poly(1-(2-acryloyloxyethyl)-3-butylimidazolium bis(trifluoromethanesulfonyl)imide) (PIL). The bulk PS–PIL structure was comprised of randomly oriented lamellar grains. However, in thin PS–PIL films (100–400 nm), the lamellae were stacked normal to the plane of the film, and islands/holes were observed when the as-prepared film thickness was incommensurate with the natural lamellar periodicity. Both of these attributes are well-known consequences of preferential wetting at surfaces. The ionic conductivity of thick PS–PIL films (50–100 μm) was approximately 20× higher in the in-plane direction than in the through-plane direction, consistent with a mixed structure comprised of randomly oriented lamellae throughout the interior of the film and highly oriented lamellae at the electrode surface. Therefore, to fully optimize the performance of a block copolymer electrolyte, it is important to consider the effects of surface interactions on the ordering of domains.