Center for Functional Nanomaterials, Brookhaven National Laboratory , Upton, New York 11973, United States.
ACS Nano. 2017 Dec 26;11(12):12326-12336. doi: 10.1021/acsnano.7b06154. Epub 2017 Dec 6.
The ubiquitous presence of thermodynamically unfavored but kinetically trapped topological defects in nanopatterns formed via self-assembly of block copolymer thin films may prevent their use for many envisioned applications. Here, we demonstrate that lamellae patterns formed by symmetric polystyrene-block-poly(methyl methacrylate) diblock copolymers self-assemble and order extremely rapidly when the diblock copolymers are blended with low molecular weight homopolymers of the constituent blocks. Being in the "wet brush" regime, the homopolymers uniformly distribute within their respective self-assembled microdomains, preventing increases in domain widths. An order-of-magnitude increase in topological grain size in blends over the neat (unblended) diblock copolymer is achieved within minutes of thermal annealing as a result of the significantly higher power law exponent for ordering kinetics in the blends. Moreover, the blends are demonstrated to be capable of rapid and robust domain alignment within micrometer-scale trenches, in contrast to the corresponding neat diblock copolymer. These results can be attributed to the lowering of energy barriers associated with domain boundaries by bringing the system closer to an order-disorder transition through low molecular weight homopolymer blending.
在通过嵌段共聚物薄膜自组装形成的纳米图案中，热力学不利但动力学捕获的拓扑缺陷普遍存在，这可能会阻止它们在许多预期应用中的使用。在这里，我们证明了当对称的聚苯乙烯-嵌段-聚（甲基丙烯酸甲酯）嵌段共聚物与组成嵌段的低分子量均聚物共混时，这些嵌段共聚物形成的片晶图案会极其迅速地自组装和有序。由于处于“湿刷”状态，均聚物在各自的自组装微区中均匀分布，从而阻止了畴宽的增加。在热退火几分钟内，由于混合物中有序动力学的幂律指数显著增加，混合物中拓扑晶粒尺寸相对于纯（未混合）嵌段共聚物增加了一个数量级。此外，与相应的纯嵌段共聚物相比，混合物被证明能够在微米级的沟槽内快速而稳健地进行畴对准。这些结果可以归因于通过低分子量均聚物共混使系统更接近有序-无序转变，从而降低了与畴界相关的能垒。
