Solution-cast films of sulfonated block copolymers are investigated for applications in water purification, gas separations, and fuel cells. It is well known that solvent composition influences the structures that form in solutions of sulfonated block copolymers and in the corresponding films. The solutions often contain trace water due to the hygroscopic nature of sulfonated polymers, and the effect of trace water on structure formation has not been previously explored. Water will drive dissociation of sulfonic acid, which in turn might accelerate the rearrangement of polymer chains by disrupting hydrogen bonds between acid groups. In this work, we examine the effects of trace water on the solution-state structure of a sulfonated pentablock copolymer (SPC) and the ultimate film morphology using small-angle X-ray scattering. The solvent used was a mixture of toluene and n-propanol with varying molar ratios of water to sulfonic acid (λ). In solutions with λ = 0, the SPC adopts a disordered structure. The addition of trace water (λ = 3.2) to SPC solutions drives a rapid self-assembly into an ordered lamellar structure. However, the presence of trace water in the solution has little effect on processing the SPC into films as water will rapidly escape from the drying film in a dry environment. For film processing, ambient humidity is more important than trace water in the solution as moisture in air provides a constant supply of water to the film as the solvent evaporates. While there are many variables that control the morphology of solution-cast SPC films, these studies demonstrate that trace amounts of water play a critical role in kinetics and thermodynamics of solution-state self-assembly and the evolution of nanoscale structures during film drying.

中文翻译：

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溶液加工过程中微量水对磺化嵌段共聚物自组装的影响

研究了磺化嵌段共聚物的溶液流延薄膜在水净化，气体分离和燃料电池中的应用。众所周知，溶剂组成会影响在磺化嵌段共聚物溶液和相应薄膜中形成的结构。由于磺化聚合物的吸湿性，溶液中通常含有痕量的水，并且痕量水对结构形成的影响以前没有被探索过。水将驱使磺酸解离，进而通过破坏酸基团之间的氢键而加速聚合物链的重排。在这项工作中，我们检查了痕量水对磺化五嵌段共聚物（SPC）溶液状态结构的影响以及使用小角度X射线散射的最终薄膜形态。ñ-丙醇的水与磺酸（λ）摩尔比变化。在λ= 0的解中，SPC采用无序结构。在SPC解决方案中添加痕量水（λ= 3.2）可以快速自组装成有序的层状结构。然而，溶液中痕量水的存在对将SPC加工成薄膜几乎没有影响，因为水会在干燥环境中迅速从干燥薄膜中逸出。对于薄膜冲洗来说，环境湿度比溶液中的痕量水更为重要，因为随着溶剂的蒸发，空气中的水分会为薄膜提供恒定的水供应。尽管有许多变量控制溶液流延SPC膜的形态，