Department of Chemical and Biomolecular Engineering, National University of Singapore , 4 Engineering Drive 4, Singapore 117576, Singapore.
Electrical and Computer Engineering Department, Duke University , Durham, North Carolina 27708, United States.
Langmuir. 2017 Nov 21;33(46):13214-13223. doi: 10.1021/acs.langmuir.7b02922. Epub 2017 Nov 7.
There are broad interests in selective and localized synthesis in nanodomains of self-assembled block copolymers (BCPs) for a variety of applications. Sequential infiltration synthesis (SIS) shows promise to selectively grow a controllable amount of materials in one type of nanodomain of a self-assembled BCP film. However, the effects of nanostructured domains in a BCP film and SIS cycles on the material growth behavior of SIS are rarely studied. In this work, we investigated the growth behavior of TiO SIS within self-assembled polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films and the two corresponding pure homopolymer films (PS and PMMA) by using in situ quartz crystal microbalance (QCM). According to the experimental results, reactant purge steps are essential to enable a high selectivity of SIS in PMMA nanodomains in the BCP films by eliminating the undesired homogeneous reactions. The continuous PS nanodomain acts as the main channel in transporting reactants to PMMA nanodomains in the self-assembled PS-b-PMMA BCP films. The segregated nanoscale PMMA nanodomains in the BCP films show dramatically different TiCl diffusion/reaction behavior than a continuous PMMA film. The mass gain per SIS cycle within PMMA nanodomains decreases quickly with increasing cycle number. After 7 TiO SIS cycles, TiO SIS can only take place at the interface between PS and PMMA nanodomains in the BCP film. The TiO SIS process can uniformly modify PMMA nanodomains throughout a self-assembled PS-b-PMMA film up to the diffusion depth owing to the unique nanostructure-enabled diffusion. SIS cycle number and chemistry of a BCP will strongly affect the material growth behavior of a SIS chemistry on the BCP film and, therefore, the final morphology of the resulting nanomaterial. Detailed studies are warranted for a SIS process on a self-assembled BCP film of different chemistry.
人们对在自组装嵌段共聚物 (BCP) 的纳米域中进行选择性和局部合成非常感兴趣，因为这在很多应用中都有很大的用处。顺序渗透合成（SIS）有望选择性地在自组装 BCP 薄膜的一种纳米域中生长可控数量的材料。然而，很少有研究关注 BCP 薄膜中的纳米结构域和 SIS 循环对 SIS 中材料生长行为的影响。在这项工作中，我们通过原位石英晶体微天平 (QCM) 研究了 TiO SIS 在自组装聚苯乙烯嵌段聚甲基丙烯酸甲酯 (PS-b-PMMA) 薄膜以及相应的两种纯均聚物薄膜 (PS 和 PMMA) 中的生长行为。根据实验结果，反应物吹扫步骤对于通过消除不需要的均相反应，在 BCP 薄膜中的 PMMA 纳米域中实现 SIS 的高选择性是必不可少的。连续的 PS 纳米域充当将反应物输送到自组装 PS-b-PMMA BCP 薄膜中 PMMA 纳米域的主要通道。在 BCP 薄膜中分离的纳米级 PMMA 纳米域表现出与连续 PMMA 薄膜截然不同的 TiCl 扩散/反应行为。每个 SIS 循环在 PMMA 纳米域中的质量增益随循环数的增加而迅速减少。在 7 个 TiO SIS 循环后，TiO SIS 只能在 BCP 薄膜中 PS 和 PMMA 纳米域的界面处进行。由于独特的纳米结构促进了扩散，TiO SIS 过程可以均匀地修饰整个自组装 PS-b-PMMA 薄膜中的 PMMA 纳米域，直至扩散深度。BCP 的 SIS 循环数和化学性质将强烈影响 SIS 化学在 BCP 薄膜上的材料生长行为，从而影响最终纳米材料的形态。因此，对于不同化学组成的自组装 BCP 薄膜上的 SIS 过程，需要进行详细的研究。
