Toth Kristof, Osuji Chinedum O, Yager Kevin G, Doerk Gregory S
Department of Chemical and Environmental Engineering, Yale University New Haven Connecticut 06520 USA.
Department of Chemical and Biomolecular Engineering, University of Pennsylvania Philadelphia Pennsylvania 19104 USA.
RSC Adv. 2020 Nov 24;10(69):42529-42541. doi: 10.1039/d0ra08491c. eCollection 2020 Nov 17.
Multicomponent blending is a convenient yet powerful approach to rationally control the material structure, morphology, and functional properties in solution-deposited films of block copolymers and other self-assembling nanomaterials. However, progress in understanding the structural and morphological dependencies on blend composition is hampered by the time and labor required to synthesize and characterize a large number of discrete samples. Here, we report a new method to systematically explore a wide composition space in ternary blends. Specifically, the blend composition space is divided into gradient segments deposited sequentially on a single wafer by a new gradient electrospray deposition tool, and characterized using high-throughput grazing-incidence small-angle X-ray scattering. This method is applied to the creation of a ternary morphology diagram for a cylinder-forming polystyrene--poly(methyl methacrylate) (PS--PMMA) block copolymer blended with PS and PMMA homopolymers. Using "wet brush" homopolymers of very low molecular weight (∼1 kg mol), we identify well-demarcated composition regions comprising highly ordered cylinder, lamellae, and sphere morphologies, as well as a disordered phase at high homopolymer mass fractions. The exquisite granularity afforded by this approach also helps to uncover systematic dependencies among self-assembled morphology, topological grain size, and domain period as functions of homopolymer mass fraction and PS : PMMA ratio. These results highlight the significant advantages afforded by blending low molecular weight homopolymers for block copolymer self-assembly. Meanwhile, the high-throughput, combinatorial approach to investigating nanomaterial blends introduced here dramatically reduces the time required to explore complex process parameter spaces and is a natural complement to recent advances in autonomous X-ray characterization.
多组分共混是一种简便而强大的方法，可用于合理控制嵌段共聚物和其他自组装纳米材料的溶液沉积薄膜中的材料结构、形态和功能特性。然而，由于合成和表征大量离散样品需要耗费时间和人力，因此在理解共混物组成对结构和形态的依赖性方面进展有限。在此，我们报告了一种系统探索三元共混物中广泛组成空间的新方法。具体而言，通过一种新型梯度电喷雾沉积工具，将共混物组成空间划分为依次沉积在单个晶片上的梯度段，并使用高通量掠入射小角X射线散射进行表征。该方法应用于制备由形成圆柱状的聚苯乙烯-聚（甲基丙烯酸甲酯）（PS-PMMA）嵌段共聚物与PS和PMMA均聚物共混而成的三元形态图。使用极低分子量（约1 kg/mol）的“湿刷”均聚物，我们确定了界限分明的组成区域，这些区域包含高度有序的圆柱、片层和球状形态，以及在高均聚物质量分数下的无序相。这种方法所提供的精细粒度还有助于揭示自组装形态、拓扑晶粒尺寸和畴周期之间作为均聚物质量分数和PS:PMMA比例函数的系统依赖性。这些结果突出了将低分子量均聚物用于嵌段共聚物自组装所带来的显著优势。同时，本文介绍的用于研究纳米材料共混物的高通量组合方法极大地减少了探索复杂工艺参数空间所需的时间，并且是对自主X射线表征方面最新进展的自然补充。
