Navarro Lucila, Thünemann Andreas F, Klinger Daniel
Institute of Pharmacy (Pharmaceutical Chemistry), Freie Universität Berlin, Königin-Luise Straße 2-4, 14195Berlin, Germany.
Bundesanstalt für Materialforschung und -prüfung (BAM), Unter den Eichen 87, 12205Berlin, Germany.
ACS Macro Lett. 2022 Mar 15;11(3):329-335. doi: 10.1021/acsmacrolett.1c00665. Epub 2022 Feb 17.
Solvent annealing is a versatile tool to adjust the shape and morphology of block copolymer (BCP) particles. During this process, polar solvents are often used for block-selective swelling. However, such water-miscible solvents can induce (partial) solubilization of one block in the surrounding aqueous medium, thus, causing complex structural variations and even particle disassembly. To reduce the complexity in morphology control, we focused on toluene as a nonpolar polystyrene-selective solvent for the annealing of striped polystyrene--poly(2-vinylpyridine) (PS--P2VP) ellipsoids. The selective stretching of PS chains produces unique asymmetric lamellae structures, which translate to an increase in the particle aspect ratio after toluene evaporation. Complete reversibility is achieved by changing to chloroform as a nonselective solvent. Moreover, surfactants can be used to tune block-selective wetting of the particle surface during the annealing; for example, a PS shell can protect the internal lamellae structure from disassembly. Overall, this versatile postassembly process enables the tailoring of the structural features of striped colloidal ellipsoids by only using commercial BCPs and solvents.
溶剂退火是一种用于调整嵌段共聚物（BCP）颗粒形状和形态的通用工具。在此过程中，极性溶剂常用于选择性溶胀嵌段。然而，这种与水混溶的溶剂会导致其中一个嵌段在周围水介质中发生（部分）溶解，从而引起复杂的结构变化甚至颗粒解体。为了降低形态控制的复杂性，我们将重点放在甲苯上，它是一种用于条纹状聚苯乙烯 - 聚（2 - 乙烯基吡啶）（PS - P2VP）椭球体退火的非极性聚苯乙烯选择性溶剂。PS链的选择性拉伸产生独特的不对称片层结构，甲苯蒸发后颗粒的长径比会增加。通过改用氯仿作为非选择性溶剂可实现完全可逆性。此外，在退火过程中可使用表面活性剂来调节颗粒表面的嵌段选择性润湿性；例如，PS壳层可保护内部片层结构不发生解体。总体而言，这种通用的后组装过程仅通过使用市售的BCP和溶剂就能实现对条纹状胶体椭球体结构特征的定制。
