Solvent Processing and Ionic Liquid-Enabled Long-Range Vertical Ordering in Block Copolymer Films with Enhanced Film Stability
Solvent Processing and Ionic Liquid-Enabled Long-Range Vertical Ordering in Block Copolymer Films with Enhanced Film Stability
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DOI：
10.1021/acs.macromol.1c01305
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发表时间：
2021-09-17
期刊：
影响因子：
5.5
通讯作者：
Karim，Alamgir
中科院分区：
文献类型：
--
作者：
Masud，Ali;Wu，Wenjie;Karim，Alamgir
在许多纳米技术应用中，形成具有薄膜几何结构的低缺陷密度有序嵌段共聚物（BCP）材料需要快速可靠的加工方法。特别是垂直排列的BCP结构，其应用范围从用于电子和光子学的纳米光刻到用于水修复的纳米孔膜和用于柔性电子的新型电池。然而，获得bcp有序相的几乎完整的垂直方向顺序仍然具有挑战性。基于溶剂的技术，如直接浸没退火（DIA）和溶剂蒸汽退火（SVA），在BCP薄膜的这些应用中具有巨大的潜力，因为它允许对其热力学、结构和链迁移率驱动的动力学特性进行“调整”。我们首先证明了DIA，使用明智的选择二元溶剂混合物，以及相对疏水的离子液体（IL），诱导聚苯乙烯-b-聚甲基丙烯酸甲酯（PS-PMMA）在片层形成嵌段共聚物薄膜中的快速垂直有序。在甲苯和庚烷的二元溶剂混合物中，IL显然为BCP本身产生了接近中性的溶剂，并为获得BCP膜内的垂直微观结构提供了有用的边界。接下来，我们证明了IL还可以抑制PS-PMMA薄膜的脱湿，从而在长时间退火后在圆柱形薄膜中使用SVA实现长时间有序。通过选择不同的溶剂条件，可以获得垂直和水平两种形态。通过调整溶剂质量和使用il等添加剂，获得具有长程无缺陷有序的增强垂直和水平BCP结构，可以使它们在许多纳米技术应用中发挥作用。
Rapid and reliable processing methods for forming ordered block copolymer (BCP) materials with low defect density in a thin film geometry are required for many nanotechnology applications. Vertically aligned BCP structures, in particular, have applications ranging from nanolithography for electronics and photonics applications to nanoporous membranes for water remediation and novel batteries for flexible electronics. However, the attainment of a nearly complete vertical orientational order of the BCP-ordered phase remains challenging. Solvent-based techniques, such as direct immersion annealing (DIA) and solvent vapor annealing (SVA), have immense potential for these applications of BCP films, as it allows for a ‘tuning’ of their thermodynamic, structural, and chain mobility-driven kinetic properties. We first demonstrate that DIA, using a judicious choice of binary solvent mixtures, along with a relatively hydrophobic ionic liquid (IL), induces the rapid vertical ordering in polystyrene-b-poly(methyl methacrylate) (PS-PMMA) in lamellae-forming block copolymer films. The IL in a binary solvent mixture with toluene and heptane apparently gives rise to a near-neutral solvent for the BCP for itself and the boundary that is useful for attaining the vertical microstructure within the BCP film. Next, we show that an IL can moreover suppress the dewetting of the PS-PMMA films to achieve long-range order using SVA in cylindrical films after long annealing times. Both vertical and horizontal morphologies are attained in these films by selecting different solvent conditions. Attaining enhanced vertical and horizontal BCP structures with long-range defect-free order by tuning solvent quality and using additives like ILs can render them useful for many nanotech applications.