Department of Chemistry and Department of Chemical Engineering & Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
ACS Appl Mater Interfaces. 2009 Dec;1(12):2812-20. doi: 10.1021/am900555f.
Concentrated solutions of poly(styrene-b-ethylene oxide) (PS-PEO) diblock copolymers were prepared using the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMI][TFSI] as the solvent. The self-assembled microstructures adopted by the copolymer solutions have been characterized using small-angle X-ray scattering. Lyotropic mesophase transitions were observed, with a progression from hexagonally packed cylinders of PEO, to lamellae, to hexagonally packed cylinders of PS upon increasing [EMI][TFSI] content. The change in lamellar domain spacing with ionic liquid concentration was found to be comparable to that reported for other block copolymers in strongly selective solvents. The ionic conductivity of the concentrated PS-PEO/[EMI][TFSI] solutions was measured via impedance spectroscopy, and ranged from 1 x 10(-7) to 1 x 10(-3) S/cm at temperatures from 25 - 100 degrees C. Additionally, the ionic conductivity of the solutions was found to increase with both ionic liquid concentration and molecular weight of the PEO blocks. The ionic conductivity of PEO homopolymer/[EMI][TFSI] solutions was also measured in order to compare the conductivity of the PS-PEO solutions to the expected limit for a lamellar sample with randomly oriented microstructure grains.
采用离子液体 1-乙基-3-甲基咪唑双（三氟甲烷磺酰基）亚胺 [EMI][TFSI] 作为溶剂，制备了聚（苯乙烯-b-氧化乙烯）（PS-PEO）嵌段共聚物的浓缩溶液。使用小角 X 射线散射对共聚物溶液采用的自组装微结构进行了表征。观察到溶致中间相转变，随着 [EMI][TFSI] 含量的增加，共聚物溶液经历了从 PEO 六方柱状堆积、到层状、再到 PS 六方柱状堆积的转变。发现随着离子液体浓度的变化，层状畴间距的变化与在强选择性溶剂中报道的其他嵌段共聚物相当。通过阻抗谱法测量了浓缩 PS-PEO/[EMI][TFSI] 溶液的离子电导率，在 25-100°C 的温度范围内，其范围为 1×10(-7) 到 1×10(-3) S/cm。此外，还发现溶液的离子电导率随着离子液体浓度和 PEO 链段的分子量的增加而增加。为了将 PS-PEO 溶液的电导率与具有随机取向微观结构晶粒的层状样品的预期极限进行比较，还测量了 PEO 均聚物/[EMI][TFSI] 溶液的离子电导率。
